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Maurice Bichara - One of the best experts on this subject based on the ideXlab platform.
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regulation by glucocorticoids and osmolality of expression of romk kir 1 1 the apical k channel of thick ascending limb
American Journal of Physiology-renal Physiology, 2003Co-Authors: Morgan Gallazzini, Amel Attmaneelakeb, Steven C Hebert, David B. Mount, Maurice BicharaAbstract:Mechanisms of regulation of ROMK channel mRNA and protein expression in medullary thick ascending limb (MTAL) were assessed in rat MTAL fragments incubated for 7 h. ROMK mRNA was quantified by quantitative RT-PCR and ROMK protein by immunoblotting analysis of crude membranes. Medium Hyperosmolality (450 mosmol/kgH2O; NaCl plus urea added to isoosmotic medium) increased ROMK mRNA (P < 0.04) and protein (P < 0.006), and 10 nM dexamethasone also increased ROMK mRNA (P < 0.02). Hyperosmolality and dexamethasone had no additive effects on ROMK mRNA. NaCl alone, but not urea or mannitol, reproduced the Hyperosmolality effect on ROMK mRNA. 1-Deamino-(8-d-arginine) vasopressin (1 nM) or 0.5 mM 8-bromo-cAMP had no effect per se on ROMK mRNA and protein. However, 8-bromo-cAMP abolished the stimulatory effect of dexamethasone on ROMK mRNA in the isoosmotic but not in the hyperosmotic medium (P < 0.004). In in vivo studies, the abundance of ROMK protein and mRNA increased in adrenalectomized (ADX) rats infused with d...
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Control of H(+)-HCO3- plasma membrane transporters by urea Hyperosmolality in rat medullary thick ascending limb.
The American journal of physiology, 1994Co-Authors: F Leviel, M Froissart, H Soualmia, J Poggioli, M Paillard, Maurice BicharaAbstract:Hyperosmolality inhibits bicarbonate absorption by the rat medullary thick ascending limb (MTAL) by unknown mechanisms. Intracellular pH (pHi) was monitored with use of 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein in rat MTAL tubule suspensions to specify the H(+)-HCO3- membrane transporters affected by Hyperosmolality. Measurements were made after > or = 15-min incubation of the cells in media rendered hypertonic by urea to avoid any change in cell volume. Na(+)-H+ antiport activity, estimated from the Na(+)-induced initial rate of pHi recovery of Na(+)-depleted acidified cells in the presence of 0.1 mM furosemide to inhibit Na(+)-K(+)-2Cl- cotransport, was inhibited by 300 mM urea and 10(-8) M arginine vasopressin (AVP) in an additive manner. Na(+)-H+ antiport inhibition by urea Hyperosmolality was maximal at 300 mM urea with a half-maximal inhibitory concentration of 75 mM and was due to a 28% decrease in maximum velocity (Vmax) with no effect on the Michaelis constant for sodium. Urea Hyperosmolality (300 mM) did not affect steady-state intracellular calcium concentration ([Ca2+]i), assessed with use of fura 2 fluorescence, and still inhibited Na(+)-H+ antiport in MTAL cells loaded with 1,2-bis(2- aminophenoxy)ethane-N,N,N',N'-tetraacetic acid to minimize any transient change in [Ca2+]i during the preincubation in urea medium. Furthermore, 300 mM urea did not stimulate basal or AVP-induced adenosine 3',5'-cyclic monophosphate (cAMP) accumulation. Plasma membrane H(+)-adenosinetriphosphatase (ATPase) activity and HCO3- transport, assessed by appropriate experimental protocols, were unaltered by 300 mM urea.(ABSTRACT TRUNCATED AT 250 WORDS)
Jarle Vaage - One of the best experts on this subject based on the ideXlab platform.
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transient Hyperosmolality modulates expression of cardiac aquaporins
Biochemical and Biophysical Research Communications, 2012Co-Authors: Arkady Rutkovskiy, Lars Henrik Mariero, Stale Nygard, Kareolav Stenslokken, Guro Valen, Jarle VaageAbstract:Abstract Purpose Hyperosmolarity is a common complication in intensive care patients, dysregulating water balance in many organs including brain and heart. The aquaporin (AQP) water channels, in particular AQP1 and −4, have been suggested to play an important role in fluid homeostasis of the myocardium. In many organs AQP expression is regulated by osmolarity, drastically altering water permeability of the cell membranes. The aim of our study was to investigate if plasma Hyperosmolality may regulate cardiac expression of AQP1 and −4, and if so, at which magnitude and time frame such regulation takes place. Methods C57Bl6 mice were injected intraperitoneally with either 1.5 ml 0.154 Mol (isoosmotic), 0.5 ml 1 Mol (mild hyperosmotic) or 0.5 ml 2 Mol (strong hyperosmotic) NaCl. Plasma, hearts, and forebrains were harvested before injection (“time 0”), and after 1, 4, 8 and 24 h. AQP1 and −4 expression were analyzed using qPCR and Western blot. Results Isoosmotic and mild hyperosmotic injections caused no important changes in cardiac AQP expression. Strong hyperosmotic NaCl injections induced an upregulation of AQP1 mRNA and glycosylated fraction of AQP1 protein in the heart without changes of the total protein. AQP4 mRNA and protein decreased in the heart and increased in the brain after hyperosmotic NaCl. The change in AQP4 protein content in the brain preceded the increase of mRNA. Conclusion As in the brain, expression of AQP1 and −4 in the heart is influenced by changes in plasma osmolality. Changes in AQP expression may alter cardiac function in hyperosmotic states.
Fumiaki Marumo - One of the best experts on this subject based on the ideXlab platform.
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Expression of aquaporin-1 in the peritoneal tissues: localization and regulation by Hyperosmolality
Peritoneal dialysis international : journal of the International Society for Peritoneal Dialysis, 2002Co-Authors: Tomoko Ota, Yoshio Terada, Michio Kuwahara, Sei Sasaki, Shuling Fan, Takashi Akiba, Fumiaki MarumoAbstract:♦ Objective: The purpose of this study was to determine the localization of the aquaporin-1 (AQP1) water channel in peritoneal tissues and the effect of Hyperosmolality on the peritoneal expression and function of AQP1. ♦ Methods: Immunohistochemical localization of AQP1 was identified in rat peritoneal tissues. Cultured rat peritoneal mesothelial cells (RPMCs) were exposed to Hyperosmolality by adding 4% glucose to the culture medium. After 1 hour, 4 hours, 24 hours, and 48 hours, AQP1 was identified by semiquantitative immunoblot and immunocytochemistry. Osmotic water permeability was measured using a light-scattering method. ♦ Results: Immunohistochemistry of rat peritoneal tissues showed the presence of AQP1 in mesothelial cells, venular endothelial cells, and capillary endothelial cells, but not in arteriole and interstitial cells. Semiquantitative immunoblot revealed that exposure to Hyperosmolality significantly increased AQP1 expression after 24 hours in whole RPMC lysates (3.3-fold at 24 hours and 3.9-fold at 48 hours). Consistent with the immunoblot, osmotic water permeability of RPMC was augmented 1.7-fold and 2.7-fold after 1 hour and 24 hours, respectively, in a hyperosmotic environment. In RPMC membrane fractions, AQP1 expression was significantly increased after 1 hour of exposure to Hyperosmolality (3.9-fold at 1 hour, 7.1-fold at 4 hours, and 8.7-fold at 24 hours). Immunocytochemistry of RPMCs showed that AQP1 was gradually redistributed from the perinuclear area to the peripheral cytoplasm, and then to the plasma membrane after a 1-hour hyperosmotic challenge, suggesting Hyperosmolality-induced translocation of AQP1. Upregulation of AQP1 was also observed in the omentum of rats loaded intraperitoneally with hyperosmotic dialysate every day for 10 weeks. ♦ Conclusion: AQP1 is widely distributed in the peritoneal cavity and may provide the major aqueous pathway across the peritoneal barrier. In addition, our findings suggested that Hyperosmolality increases AQP1-dependent water permeability in peritoneal tissues by regulating the translocation and synthesis of AQP1 protein.
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Sequential activation of Raf-1 kinase, mitogen-activated protein (MAP) kinase kinase, MAP kinase, and S6 kinase by Hyperosmolality in renal cells.
The Journal of biological chemistry, 1994Co-Authors: Yoshio Terada, Hiroshi Nonoguchi, Kimio Tomita, Sei Sasaki, Miwako K. Homma, Tiaxin Yang, Takehisa Yamada, Yasuhito Yuasa, Edwin G. Krebs, Fumiaki MarumoAbstract:In the renal medulla during antidiuresis, the extracellular fluid becomes hyperosmotic. Madin-Darby canine kidney (MDCK) epithelial cells adapt in hyperosmotic conditions and serve as a useful tissue culture model for cellular responses to Hyperosmolality. We demonstrate that Hyperosmolality stimulates phospholipase C, Raf-1 kinase mitogen-activated protein (MAP) kinase kinase, MAP kinase, and S6 kinase activities and that it increases phosphorylation of Raf-1 kinase, and p42 MAP kinase in MDCK cells. Stimulation of these kinases is osmolality-dependent (from 300 to 600 mosm/kg H2O). The time course of activation is sequential; the peak stimulation for Raf-1 kinase is at 5 min, at 10 min for MAP kinase kinase and MAP kinase, and at 20 min for S6 kinase. The activation of Raf-1 kinase and MAP kinase is inhibited by phorbol 12-myristate 13-acetate pretreatment in the presence of calphostin C or H-7. Tyrosine kinase inhibitors (genistein, herbimycin) do not significantly suppress Hyperosmolality-induced MAP kinase activity. The increase of Ins-1,4,5-P3 levels by Hyperosmolality suggests that activation of these kinases is mediated at least partially via activation of phospholipase C. Thus, Hyperosmolality stimulates the serine/threonine kinases, Raf-1 kinase, MAP kinase kinase, MAP kinase, and S6 kinase, via predominantly protein kinase C-dependent, tyrosine kinase-independent pathways in MDCK cells.
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Effects of Hyperosmolality on ANP-stimulated cGMP generation in rat inner medullary collecting duct
Kidney international, 1994Co-Authors: Masanori Shinohara, Yoshio Terada, Hiroshi Nonoguchi, Kazutomo Ujiie, Kimio Tomita, Akira Owada, Fumiaki MarumoAbstract:Effects of Hyperosmolality on ANP-stimulated cGMP generation in rat inner medullary collecting duct. The innner medullary collecting duct (IMCD) is a major target site of atrial natriuretic peptide (ANP) for diuresis and natriuresis, and it is in a hypertonic condition made by the renal countercurrent multiplication system. We investigated the effects of Hyperosmolality on ANP-stimulated cGMP generation in IMCD and glomerulus. Hypertonic solutions (490 and 690 mOsm/kg · H 2 O) were made by adding NaCl or urea to isotonic solution (290 mOsm/ kg · H 2 O). Hypertonicity of 490 mOsm/kg · H 2 O using NaCl reduced both ANP-stimulated guanylate cyclase activity (from 7.7 ± 1.1 to 4.1 ± 0.5 fmol/mm/5 min) and cGMP generation (from 1.35 ± 0.18 to 0.48 ± 0.20 fmol/mm/3 min) in IMCD. Hypertonicity of 690 mOsm/kg · H 2 O using NaCl did not further reduce ANP-stimulated cGMP generation in IMCD. Hypertonicity using urea also inhibited ANP-stimulated guanylate cyclase activity and cGMP generation in IMCD. On the other hand, hypertonicity using NaCl stimulated AVP-stimulated cAMP generation in IMCD, while hypertonicity using urea reduced it. In glomeruli, Hyperosmolality of 490 mOsm/kg · H 2 O using NaCl also reduced ANP-stimulated cGMP generation, and hypertonicity of 690 mOsm/kg · H 2 O using NaCl further reduced it. In summary, Hyperosmolality using NaCl and urea inhibited ANP-sensitive guanylate cyclase activity and cGMP generation both in IMCD and glomeruli. However, the mechanisms at work may be different between NaCl and urea.
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Effect of Hyperosmolality on production and mRNA expression of ET-1 in inner medullary collecting duct
American Journal of Physiology-Renal Physiology, 1993Co-Authors: Tianxin Yang, Yoshio Terada, Hiroshi Nonoguchi, Kazutomo Ujiie, Kimio Tomita, Fumiaki MarumoAbstract:The effects of Hyperosmolality on the production and mRNA expression of endothelin-1 (ET-1) in inner medullary collecting duct (IMCD) were examined in the present study. Osmolality in incubation media was changed from 290 to 490 or 690 mosmol/kgH2O by adding NaCl, urea, mannitol, or raffinose. A preliminary experiment was carried out using tubule suspension from the inner medulla. Hyperosmolality by NaCl stimulated ET-1 accumulation in rats (from 323.5 +/- 76.3 to 478.0 +/- 108.4 and 573.7 +/- 47.8 pg.mg protein-1 x 24 h-1 in 290, 490, and 690 mosmol/kgH2O, respectively) and rabbits. In contrast, Hyperosmolality by urea markedly decreased ET-1 accumulation and Hyperosmolality by mannitol showed no effect on it. We next examined whether Hyperosmolality changes ET-1 mRNA. After incubation in isotonic or hypertonic solution for 6 h, ET-1 mRNA was determined using reverse transcription and polymerase chain reaction (PCR) in microdissected IMCD and glomerulus. Hyperosmolality by NaCl and raffinose significantly increased the PCR products of ET-1 mRNA in IMCD, whereas mannitol did not. The stimulatory effect of Hyperosmolality by NaCl on ET-1 mRNA expression was not observed in glomerulus. Our data suggested a stimulatory effect of Hyperosmolality on production and mRNA expression of ET-1 in IMCD but not in glomerulus.
Dietmar Kültz - One of the best experts on this subject based on the ideXlab platform.
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gadd45 proteins induce g2 m arrest and modulate apoptosis in kidney cells exposed to hyperosmotic stress
Journal of Biological Chemistry, 2004Co-Authors: Dietmar KültzAbstract:Abstract Gadd45 proteins are induced by Hyperosmolality in renal inner medullary (IM) cells, but their role for cell adaptation to osmotic stress is not known. We show that a cell line derived from murine renal IM cells responds to moderate hyperosmotic stress (540 mosmol/kg) by activation of G2/M arrest without significant apoptosis. If the severity of hyperosmotic stress exceeds the tolerance limit of this cell line (620 mosmol/kg) apoptosis is strongly induced. Using transient overexpression of ectopic Gadd45 proteins and simultaneous analysis of transfected versus non-transfected cells by laser-scanning cytometry, we were able to measure the effects of Gadd45 super-induction during Hyperosmolality on G2/M arrest and apoptosis. Our results demonstrate that induction of all three Gadd45 isoforms inhibits mitosis and promotes G2/M arrest during moderate hyperosmotic stress but not in isosmotic controls. Furthermore, all three Gadd45 proteins are also involved in control of apoptosis during severe hyperosmotic stress. Under these conditions Gadd45γ induction strongly potentiates apoptosis. In contrast, Gadd45α/β induction transiently increases caspase 3/7 and annexin V binding before 12 h but inhibits later stages of apoptosis during severe Hyperosmolality. These results show that Gadd45 isoforms function in common but also in distinct pathways during Hyperosmolality and that their increased abundance contributes to the low mitotic index and protection of genomic integrity in cells of the mammalian renal inner medulla.
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Gadd45 Proteins Induce G2/M Arrest and Modulate Apoptosis in Kidney Cells Exposed to Hyperosmotic Stress
Journal of Biological Chemistry, 2004Co-Authors: Dietmar KültzAbstract:Abstract Gadd45 proteins are induced by Hyperosmolality in renal inner medullary (IM) cells, but their role for cell adaptation to osmotic stress is not known. We show that a cell line derived from murine renal IM cells responds to moderate hyperosmotic stress (540 mosmol/kg) by activation of G2/M arrest without significant apoptosis. If the severity of hyperosmotic stress exceeds the tolerance limit of this cell line (620 mosmol/kg) apoptosis is strongly induced. Using transient overexpression of ectopic Gadd45 proteins and simultaneous analysis of transfected versus non-transfected cells by laser-scanning cytometry, we were able to measure the effects of Gadd45 super-induction during Hyperosmolality on G2/M arrest and apoptosis. Our results demonstrate that induction of all three Gadd45 isoforms inhibits mitosis and promotes G2/M arrest during moderate hyperosmotic stress but not in isosmotic controls. Furthermore, all three Gadd45 proteins are also involved in control of apoptosis during severe hyperosmotic stress. Under these conditions Gadd45γ induction strongly potentiates apoptosis. In contrast, Gadd45α/β induction transiently increases caspase 3/7 and annexin V binding before 12 h but inhibits later stages of apoptosis during severe Hyperosmolality. These results show that Gadd45 isoforms function in common but also in distinct pathways during Hyperosmolality and that their increased abundance contributes to the low mitotic index and protection of genomic integrity in cells of the mammalian renal inner medulla.
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Hyperosmolality triggers oxidative damage in kidney cells
Proceedings of the National Academy of Sciences of the United States of America, 2004Co-Authors: Dietmar KültzAbstract:The intracellular milieu, including solute composition and concentration of important electrolytes, is carefully tuned to support metabolism and other vital cell functions. In addition, cell volume is tightly regulated. A change in extracellular osmolality disturbs the delicate balance that maintains intracellular solute composition and cell volume. To counteract deleterious consequences of such disturbance, cells have evolved a universal mechanism to respond to osmotic stress by cell volume regulation (1) and adaptive adjustment of compatible organic osmolyte levels (2). However, these adaptive responses are not instantaneous, and osmotic stress causes significant damage to proteins (3) and DNA (4). Such damage can persist until hyperosmotic stress diminishes (5). In this issue of PNAS, Zhang et al. (6) demonstrate that at least part of the hyperosmotic damage to proteins and DNA is caused by secondary oxidative stress. Zhang et al. report the thought-provoking observation that Hyperosmolality increases reactive oxygen species (ROS) and protein carbonylation levels in renal inner medullary (IM) cells in vitro and in vivo . This observation significantly extends our understanding of the molecular nature of the hyperosmotic threat to cells. The work by Zhang et al. also identifies ROS and protein carbonylation as potential signaling intermediates for osmosensory signal transduction. ### Consequences of Hyperosmolality Renal IM cells of mammals are routinely exposed to osmotic fluctuations as a result of the renal concentrating mechanism. Changes in renal urinary concentration and excretion reflect the degree of systemic hydration and salt load. They are based on adjustments of NaCl and urea concentrations in the renal IM. Thus, Hyperosmolality in the renal IM is mainly a result of increased concentrations of NaCl and urea. These two major osmolytes have very different effects on cells. First, NaCl does not readily permeate the cell membrane, and Hyperosmolality in the form of elevated extracellular NaCl leads …
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Hyperosmolality in the form of elevated NaCl but not urea causes DNA damage in murine kidney cells
Proceedings of the National Academy of Sciences of the United States of America, 2001Co-Authors: Dietmar Kültz, Devulapalli ChakravartyAbstract:This study demonstrates, by using neutral comet assay and pulsed field gel electrophoresis, that hyperosmotic stress causes DNA damage in the form of double strand breaks (dsb). Different solutes increase the rate of DNA dsb to different degrees at identical strengths of Hyperosmolality. Hyperosmolality in the form of elevated NaCl (HNa) is most potent in this regard, whereas Hyperosmolality in the form of elevated urea (HU) does not cause DNA dsb. The amount of DNA dsb increases significantly as early as 15 min after the onset of HNa. By using neutral comet and DNA ladder assays, we show that this rapid induction of DNA damage is not attributable to apoptosis. We demonstrate that renal inner medullary cells are able to efficiently repair hyperosmotic DNA damage within 48 h after exposure to Hyperosmolality. DNA repair correlates with cell survival and is repressed by 25 μM LY294002, an inhibitor of DNA-activated protein kinases. These results strongly suggest that the hyperosmotic stress resistance of renal inner medullary cells is based not only on adaptations that protect cellular proteins from osmotic damage but, in addition, on adaptations that compensate DNA damage and maintain genomic integrity.
Yoshio Terada - One of the best experts on this subject based on the ideXlab platform.
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Expression of aquaporin-1 in the peritoneal tissues: localization and regulation by Hyperosmolality
Peritoneal dialysis international : journal of the International Society for Peritoneal Dialysis, 2002Co-Authors: Tomoko Ota, Yoshio Terada, Michio Kuwahara, Sei Sasaki, Shuling Fan, Takashi Akiba, Fumiaki MarumoAbstract:♦ Objective: The purpose of this study was to determine the localization of the aquaporin-1 (AQP1) water channel in peritoneal tissues and the effect of Hyperosmolality on the peritoneal expression and function of AQP1. ♦ Methods: Immunohistochemical localization of AQP1 was identified in rat peritoneal tissues. Cultured rat peritoneal mesothelial cells (RPMCs) were exposed to Hyperosmolality by adding 4% glucose to the culture medium. After 1 hour, 4 hours, 24 hours, and 48 hours, AQP1 was identified by semiquantitative immunoblot and immunocytochemistry. Osmotic water permeability was measured using a light-scattering method. ♦ Results: Immunohistochemistry of rat peritoneal tissues showed the presence of AQP1 in mesothelial cells, venular endothelial cells, and capillary endothelial cells, but not in arteriole and interstitial cells. Semiquantitative immunoblot revealed that exposure to Hyperosmolality significantly increased AQP1 expression after 24 hours in whole RPMC lysates (3.3-fold at 24 hours and 3.9-fold at 48 hours). Consistent with the immunoblot, osmotic water permeability of RPMC was augmented 1.7-fold and 2.7-fold after 1 hour and 24 hours, respectively, in a hyperosmotic environment. In RPMC membrane fractions, AQP1 expression was significantly increased after 1 hour of exposure to Hyperosmolality (3.9-fold at 1 hour, 7.1-fold at 4 hours, and 8.7-fold at 24 hours). Immunocytochemistry of RPMCs showed that AQP1 was gradually redistributed from the perinuclear area to the peripheral cytoplasm, and then to the plasma membrane after a 1-hour hyperosmotic challenge, suggesting Hyperosmolality-induced translocation of AQP1. Upregulation of AQP1 was also observed in the omentum of rats loaded intraperitoneally with hyperosmotic dialysate every day for 10 weeks. ♦ Conclusion: AQP1 is widely distributed in the peritoneal cavity and may provide the major aqueous pathway across the peritoneal barrier. In addition, our findings suggested that Hyperosmolality increases AQP1-dependent water permeability in peritoneal tissues by regulating the translocation and synthesis of AQP1 protein.
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Hyperosmolality activates Akt and regulates apoptosis in renal tubular cells
Kidney international, 2001Co-Authors: Yoshio Terada, Seiji Inoshita, Satoko Hanada, Haruko Shimamura, Michio Kuwahara, Wataru Ogawa, Masato Kasuga, Sei Sasaki, F MarumoAbstract:Hyperosmolality activates Akt and regulates apoptosis in renal tubular cells . Background The novel serine-threonine kinase Akt is a critical enzyme in cell survival. We investigated the roles of the Akt pathway and apoptotic signals in ( 1 ) Madin-Darby canine kidney (MDCK) cells in a hyperosmotic condition in vitro and ( 2 ) in the inner medulla of dehydrated rat in vivo. Methods The in vivo experiments were performed in 24- and 48-hour water-restricted rats. Hyperosmolality-stimulated Akt phosphorylation was examined in MDCK cells. Phosphatidylinositol 3-kinase (PI3-K) inhibitors, the dominant-negative mutant of PI3-K, the dominant-negative mutant of Akt, and the dominant-active form of Akt were used to examine the roles of the PI3-K/Akt pathways in renal tubular cell apoptosis. Results The amount of phosphorylated Akt protein was increased in the inner medulla of dehydrated rats. Hyperosmolality induced by the addition of NaCl, urea, and raffinose phosphorylated Akt in MDCK cells in an osmolality-dependent manner. PI3-K inhibitors and the dominant-negative mutant of PI3-K inhibited the Hyperosmolality-induced phosphorylation of Akt. Raising the media osmolality from a normal level to 500 or 600 mOsm/kg H 2 O final osmolality elicited apoptotic changes such as nucleosomal laddering of DNA and an increment of caspase-3 activity and increased activity in the cell death enzyme-linked immunosorbent assay. Dominant-active Akt prevented the mild Hyperosmolality-induced apoptosis, while inhibition of the PI3-K/Akt pathways promoted apoptosis. Conclusion The Akt pathway is activated by Hyperosmolality in vitro and in vivo, and activation of Akt prevents the mild Hyperosmolality-induced apoptotic changes in MDCK cells. PI3-K/Akt pathways are involved in a hypertonic condition that confers the balance between cell survival and apoptosis.
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Sequential activation of Raf-1 kinase, mitogen-activated protein (MAP) kinase kinase, MAP kinase, and S6 kinase by Hyperosmolality in renal cells.
The Journal of biological chemistry, 1994Co-Authors: Yoshio Terada, Hiroshi Nonoguchi, Kimio Tomita, Sei Sasaki, Miwako K. Homma, Tiaxin Yang, Takehisa Yamada, Yasuhito Yuasa, Edwin G. Krebs, Fumiaki MarumoAbstract:In the renal medulla during antidiuresis, the extracellular fluid becomes hyperosmotic. Madin-Darby canine kidney (MDCK) epithelial cells adapt in hyperosmotic conditions and serve as a useful tissue culture model for cellular responses to Hyperosmolality. We demonstrate that Hyperosmolality stimulates phospholipase C, Raf-1 kinase mitogen-activated protein (MAP) kinase kinase, MAP kinase, and S6 kinase activities and that it increases phosphorylation of Raf-1 kinase, and p42 MAP kinase in MDCK cells. Stimulation of these kinases is osmolality-dependent (from 300 to 600 mosm/kg H2O). The time course of activation is sequential; the peak stimulation for Raf-1 kinase is at 5 min, at 10 min for MAP kinase kinase and MAP kinase, and at 20 min for S6 kinase. The activation of Raf-1 kinase and MAP kinase is inhibited by phorbol 12-myristate 13-acetate pretreatment in the presence of calphostin C or H-7. Tyrosine kinase inhibitors (genistein, herbimycin) do not significantly suppress Hyperosmolality-induced MAP kinase activity. The increase of Ins-1,4,5-P3 levels by Hyperosmolality suggests that activation of these kinases is mediated at least partially via activation of phospholipase C. Thus, Hyperosmolality stimulates the serine/threonine kinases, Raf-1 kinase, MAP kinase kinase, MAP kinase, and S6 kinase, via predominantly protein kinase C-dependent, tyrosine kinase-independent pathways in MDCK cells.
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Effects of Hyperosmolality on ANP-stimulated cGMP generation in rat inner medullary collecting duct
Kidney international, 1994Co-Authors: Masanori Shinohara, Yoshio Terada, Hiroshi Nonoguchi, Kazutomo Ujiie, Kimio Tomita, Akira Owada, Fumiaki MarumoAbstract:Effects of Hyperosmolality on ANP-stimulated cGMP generation in rat inner medullary collecting duct. The innner medullary collecting duct (IMCD) is a major target site of atrial natriuretic peptide (ANP) for diuresis and natriuresis, and it is in a hypertonic condition made by the renal countercurrent multiplication system. We investigated the effects of Hyperosmolality on ANP-stimulated cGMP generation in IMCD and glomerulus. Hypertonic solutions (490 and 690 mOsm/kg · H 2 O) were made by adding NaCl or urea to isotonic solution (290 mOsm/ kg · H 2 O). Hypertonicity of 490 mOsm/kg · H 2 O using NaCl reduced both ANP-stimulated guanylate cyclase activity (from 7.7 ± 1.1 to 4.1 ± 0.5 fmol/mm/5 min) and cGMP generation (from 1.35 ± 0.18 to 0.48 ± 0.20 fmol/mm/3 min) in IMCD. Hypertonicity of 690 mOsm/kg · H 2 O using NaCl did not further reduce ANP-stimulated cGMP generation in IMCD. Hypertonicity using urea also inhibited ANP-stimulated guanylate cyclase activity and cGMP generation in IMCD. On the other hand, hypertonicity using NaCl stimulated AVP-stimulated cAMP generation in IMCD, while hypertonicity using urea reduced it. In glomeruli, Hyperosmolality of 490 mOsm/kg · H 2 O using NaCl also reduced ANP-stimulated cGMP generation, and hypertonicity of 690 mOsm/kg · H 2 O using NaCl further reduced it. In summary, Hyperosmolality using NaCl and urea inhibited ANP-sensitive guanylate cyclase activity and cGMP generation both in IMCD and glomeruli. However, the mechanisms at work may be different between NaCl and urea.
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Effect of Hyperosmolality on production and mRNA expression of ET-1 in inner medullary collecting duct
American Journal of Physiology-Renal Physiology, 1993Co-Authors: Tianxin Yang, Yoshio Terada, Hiroshi Nonoguchi, Kazutomo Ujiie, Kimio Tomita, Fumiaki MarumoAbstract:The effects of Hyperosmolality on the production and mRNA expression of endothelin-1 (ET-1) in inner medullary collecting duct (IMCD) were examined in the present study. Osmolality in incubation media was changed from 290 to 490 or 690 mosmol/kgH2O by adding NaCl, urea, mannitol, or raffinose. A preliminary experiment was carried out using tubule suspension from the inner medulla. Hyperosmolality by NaCl stimulated ET-1 accumulation in rats (from 323.5 +/- 76.3 to 478.0 +/- 108.4 and 573.7 +/- 47.8 pg.mg protein-1 x 24 h-1 in 290, 490, and 690 mosmol/kgH2O, respectively) and rabbits. In contrast, Hyperosmolality by urea markedly decreased ET-1 accumulation and Hyperosmolality by mannitol showed no effect on it. We next examined whether Hyperosmolality changes ET-1 mRNA. After incubation in isotonic or hypertonic solution for 6 h, ET-1 mRNA was determined using reverse transcription and polymerase chain reaction (PCR) in microdissected IMCD and glomerulus. Hyperosmolality by NaCl and raffinose significantly increased the PCR products of ET-1 mRNA in IMCD, whereas mannitol did not. The stimulatory effect of Hyperosmolality by NaCl on ET-1 mRNA expression was not observed in glomerulus. Our data suggested a stimulatory effect of Hyperosmolality on production and mRNA expression of ET-1 in IMCD but not in glomerulus.