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J Marchetti - One of the best experts on this subject based on the ideXlab platform.
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the parietal sheet of bowman s capsule of rat renal glomerulus a target of endothelin and paf
American Journal of Physiology-renal Physiology, 1995Co-Authors: J Marchetti, F. Lebrun, P Meneton, May Blochfaure, R M RajerisonAbstract:On the basis of intracellular Calcium concentration ([Ca 2+ ] i ) measurements, we have previously reported that the parietal sheet of Bowman's capsule was sensitive to cholinergic agonists. The aim of the present work was to investigate whether this structure could be also a target of endothelin and platelet activating factor (PAF), since we observed [Ca 2+ ] i increases in response to both agonists in the glomerulus, but which were very different from that induced by carbachol. For this purpose, we measured [Ca 2+ ] i on single microdissected parietal sheets, using a fura 2 microfluorescence technique and compared the effects of maximal concentrations of the three agonists (10 −7 , 10 −8 , and 10 −4 M for endothelin, PAF, and carbachol, respectively) under various experimental conditions. We observed that, like in the glomerulus, endothelin and PAF induced, in the parietal sheet, [Ca 2+ ] i responses that differed in many respects from those found with carbachol. Thus, in the presence of 2 mM External Calcium, 1) endothelin and PAF responses spontaneously declined to basal level, whereas a stationary plateau was observed after a sharp peak of [Ca 2+ ] i with carbachol; 2) the magnitude of [Ca 2+ ] i peak was smaller with endothelin and PAF than with carbachol; and 3) endothelin and PAF, but not carbachol, induced a homologous dose-dependent desensitization. Moreover, in the absence of External Calcium, endothelin and PAF responses were smaller than carbachol response, although all three responses apparently resulted from release of Calcium ions from the same internal pool. In additional experiments, we observed that, like carbachol, endothelin and PAF contracted the parietal sheet, which is only composed of myoepithelial cells. In conclusion, three agonists, namely carbachol, endothelin, and PAF, are now known to act on the parietal sheet by increasing [Ca 2 ] i and inducing contractions
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The parietal sheet of Bowman's capsule of rat renal glomerulus: a target of endothelin and PAF.
The American journal of physiology, 1995Co-Authors: J Marchetti, F. Lebrun, P Meneton, M Bloch-faure, R M RajerisonAbstract:On the basis of intracellular Calcium concentration ([Ca2+]i) measurements, we have previously reported that the parietal sheet of Bowman's capsule was sensitive to cholinergic agonists. The aim of the present work was to investigate whether this structure could be also a target of endothelin and platelet-activating factor (PAF), since we observed [Ca2+]i increases in response to both agonists in the glomerulus, but which were very different from that induced by carbachol. For this purpose, we measured [Ca2+]i on single microdissected parietal sheets, using a fura 2 microfluorescence technique and compared the effects of maximal concentrations of the three agonists (10(-7), 10(-8), and 10(-4) M for endothelin, PAF, and carbachol, respectively) under various experimental conditions. We observed that, like in the glomerulus, endothelin and PAF induced, in the parietal sheet, [Ca2+]i responses that differed in many respects from those found with carbachol. Thus, in the presence of 2 mM External Calcium, 1) endothelin and PAF responses spontaneously declined to basal level, whereas a stationary plateau was observed after a sharp peak of [Ca2+]i with carbachol; 2) the magnitude of [Ca2+]i peak was smaller with endothelin and PAF than with carbachol; and 3) endothelin and PAF, but not carbachol, induced a homologous dose-dependent desensitization. Moreover, in the absence of External Calcium, endothelin and PAF responses were smaller than carbachol response, although all three responses apparently resulted from release of Calcium ions from the same internal pool. In additional experiments, we observed that, like carbachol, endothelin and PAF contracted the parietal sheet, which is only composed of myoepithelial cells.(ABSTRACT TRUNCATED AT 250 WORDS)
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cholinergic effects on intracellular free Calcium concentration in renal corpuscle role of parietal sheet
American Journal of Physiology-renal Physiology, 1992Co-Authors: F. Lebrun, G Vassent, F. Morel, J MarchettiAbstract:: To investigate a possible effect of cholinergic agonists on the renal glomerular function, fura-2 microfluorometric measurements of intracellular free Calcium [( Ca2+]i) were performed on single intact glomeruli, single isolated parietal sheets of the Bowman's capsule and single parietal sheet-deprived glomeruli (PS-D glomerulus). Carbachol (10(-4) M), in the presence of 2 mM External Calcium, induced a biphasic increase in [Ca2+]i characterized by a sharp initial peak followed by a sustained plateau in the whole glomerulus (delta [Ca2+]i = 177 +/- 13 and 70 +/- 7 nM, respectively; n = 21) and in the parietal sheet (418 +/- 30 and 111 +/- 13 nM, respectively; n = 21). In the PS-D glomerulus (n = 9), the response was less marked and included a barely visible peak (77 +/- 13 nM) and a relatively low plateau (49 +/- 11 nM). In the absence of External Calcium, the peak phase was preserved in the three structures, indicating a Calcium release from intracellular pools, whereas the plateau, due to the entry of External Calcium, was suppressed. These effects were fully inhibited by 10(-4) M of either atropine or pirenzepine, demonstrating the muscarinic nature of the receptors. Dose-response curves showed that the parietal sheet was more sensitive to the physiological agonist (acetylcholine) than to carbachol. A still unexplained difference in sensitivity was noted between peak and plateau, respectively (half-maximal responses were 5 x 10(-6) vs. 5 x 10(-7) M for carbachol and 2 x 10(-7) vs. 3 x 10(-8) M for acetylcholine).(ABSTRACT TRUNCATED AT 250 WORDS)
Marco T Gonzalezmartinez - One of the best experts on this subject based on the ideXlab platform.
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sodium influx induced by External Calcium chelation decreases human sperm motility
Human Reproduction, 2011Co-Authors: Victor Torresflores, Giovanni Picazojuarez, Yadira Libertad Hernandezrueda, Alberto Darszon, Marco T GonzalezmartinezAbstract:BACKGROUND Calcium removal from the medium promptly reduces human sperm motility and induces a Na(+)-dependent depolarization that is accompanied by an increase in intracellular sodium concentration ([Na(+)](i)) and a decrease in intracellular Calcium concentration ([Ca(2+)](i)). Sodium loading activates a Na(+)/K(+)-ATPase. METHODS Membrane potential (Vm) and [Ca(2+)](i) were simultaneously detected in human sperm populations with the fluorescent probes diSC(3)(5) and fura 2. [Na(+)](i) and was measured independently in a similar fashion using sodium-binding benzofuran isophthalate. Motility was determined in a CASA system, ATP was measured using the luciferin-luciferase assay, and cAMP was measured by radioimmunoassay. RESULTS Human sperm motility reduction after Calcium removal is related to either Na(+)-loading or Na(+)-dependent depolarization, because, under conditions that inhibit the Calcium removal-induced Na(+)-dependent depolarization and [Na(+)](i) increase, sperm motility was unaffected. By clamping sperm Vm with valinomycin, we found that the motility reduction associated with the Calcium removal was related to sodium loading, and not to membrane potential depolarization. Mibefradil, a Calcium channel blocker, markedly inhibited the Na(+)-dependent depolarization and sodium loading, and also preserved sperm motility. In the absence of Calcium, both ATP and cAMP concentrations were decreased by 40%. However ATP levels were unchanged when Calcium removal was performed under conditions that inhibit the Calcium removal-induced Na(+)-dependent depolarization and [Na(+)](i) increase. CONCLUSIONS Human sperm motility arrest induced by External Calcium removal is mediated principally by sodium loading, which would stimulate the Na(+)/K(+)-ATPase and in turn deplete the ATP content.
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intracellular sodium increase induced by External Calcium removal in human sperm
Journal of Andrology, 2008Co-Authors: Victor Torresflores, Norma L Garciasanchez, Marco T GonzalezmartinezAbstract:In human sperm, removal of External Calcium produces a fast Na(+)-dependent depolarization that is presumably due to sodium permeation through Calcium channels. Calcium restoration produces a ouabain-sensitive hyperpolarization that brings the membrane potential to values frequently more negative than resting. In this work, we show evidence indicating that External Calcium removal induces an increase in the intracellular sodium ([Na(+)](i)) and that this phenomenon is related to the Na(+)-dependent depolarization. Calcium restoration blocked the [Na(+)](i) increase and then produced a slow decrease that was inhibited by ouabain. The [Na(+)](i) increase was inhibited by nanomolar-micromolar Calcium or by millimolar magnesium, which has been previously shown to inhibit the Na(+)-dependent depolarization. This evidence supports the hypothesis that, in zero-Calcium medium, a Calcium channel that would contribute to resting intracellular Calcium levels allows sodium permeation, producing depolarization and a significant [Na(+)](i) increase. Sodium loading would stimulate the Na(+),K(+)-ATPase, the activity of which contributes to the sperm hyperpolarization observed upon Calcium restoration.
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induction of a sodium dependent depolarization by External Calcium removal in human sperm
Journal of Biological Chemistry, 2003Co-Authors: Marco T GonzalezmartinezAbstract:Abstract Removal of External Calcium with EGTA (from 2.5 mm to nanomolar levels) caused a remarkable depolarization in human sperm. This depolarization was initially fast. It was followed by a slow phase that brought the Vm to values of over 0 mV in 1–2 min. The slow and sustained phase correlated with a sustained decrease in intracellular Calcium. However, Calcium removal still induced depolarization in sperm with enhanced intracellular Calcium (induced by progesterone), indicating that the sustained depolarization was not caused by a sustained intracellular Calcium decrease. The depolarization was reduced as the External sodium content was substituted with choline, indicating that it was due to a sodium current, and was observed in lithium but not in tetramethylammonium-containing medium. In low sodium medium, the addition of sodium after Calcium removal induced depolarization to the extent of which slightly increased in 2 min. The depolarization was completely inhibited by External magnesium (Ki = 1.16 mm). The addition of Calcium or magnesium to Calcium removal-induced depolarized sperm induced hyperpolarization that was inhibited by ouabain and was also prevented in medium without potassium, suggesting that the activity of the electrogenic Na+,K+-ATPase was involved. The conductance activated by Calcium removal might unveil the presence of a Calcium channel that in the absence of External Calcium allows sodium permeation and that in normal conditions might contribute to the resting intracellular Calcium concentration.
F. Lebrun - One of the best experts on this subject based on the ideXlab platform.
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the parietal sheet of bowman s capsule of rat renal glomerulus a target of endothelin and paf
American Journal of Physiology-renal Physiology, 1995Co-Authors: J Marchetti, F. Lebrun, P Meneton, May Blochfaure, R M RajerisonAbstract:On the basis of intracellular Calcium concentration ([Ca 2+ ] i ) measurements, we have previously reported that the parietal sheet of Bowman's capsule was sensitive to cholinergic agonists. The aim of the present work was to investigate whether this structure could be also a target of endothelin and platelet activating factor (PAF), since we observed [Ca 2+ ] i increases in response to both agonists in the glomerulus, but which were very different from that induced by carbachol. For this purpose, we measured [Ca 2+ ] i on single microdissected parietal sheets, using a fura 2 microfluorescence technique and compared the effects of maximal concentrations of the three agonists (10 −7 , 10 −8 , and 10 −4 M for endothelin, PAF, and carbachol, respectively) under various experimental conditions. We observed that, like in the glomerulus, endothelin and PAF induced, in the parietal sheet, [Ca 2+ ] i responses that differed in many respects from those found with carbachol. Thus, in the presence of 2 mM External Calcium, 1) endothelin and PAF responses spontaneously declined to basal level, whereas a stationary plateau was observed after a sharp peak of [Ca 2+ ] i with carbachol; 2) the magnitude of [Ca 2+ ] i peak was smaller with endothelin and PAF than with carbachol; and 3) endothelin and PAF, but not carbachol, induced a homologous dose-dependent desensitization. Moreover, in the absence of External Calcium, endothelin and PAF responses were smaller than carbachol response, although all three responses apparently resulted from release of Calcium ions from the same internal pool. In additional experiments, we observed that, like carbachol, endothelin and PAF contracted the parietal sheet, which is only composed of myoepithelial cells. In conclusion, three agonists, namely carbachol, endothelin, and PAF, are now known to act on the parietal sheet by increasing [Ca 2 ] i and inducing contractions
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The parietal sheet of Bowman's capsule of rat renal glomerulus: a target of endothelin and PAF.
The American journal of physiology, 1995Co-Authors: J Marchetti, F. Lebrun, P Meneton, M Bloch-faure, R M RajerisonAbstract:On the basis of intracellular Calcium concentration ([Ca2+]i) measurements, we have previously reported that the parietal sheet of Bowman's capsule was sensitive to cholinergic agonists. The aim of the present work was to investigate whether this structure could be also a target of endothelin and platelet-activating factor (PAF), since we observed [Ca2+]i increases in response to both agonists in the glomerulus, but which were very different from that induced by carbachol. For this purpose, we measured [Ca2+]i on single microdissected parietal sheets, using a fura 2 microfluorescence technique and compared the effects of maximal concentrations of the three agonists (10(-7), 10(-8), and 10(-4) M for endothelin, PAF, and carbachol, respectively) under various experimental conditions. We observed that, like in the glomerulus, endothelin and PAF induced, in the parietal sheet, [Ca2+]i responses that differed in many respects from those found with carbachol. Thus, in the presence of 2 mM External Calcium, 1) endothelin and PAF responses spontaneously declined to basal level, whereas a stationary plateau was observed after a sharp peak of [Ca2+]i with carbachol; 2) the magnitude of [Ca2+]i peak was smaller with endothelin and PAF than with carbachol; and 3) endothelin and PAF, but not carbachol, induced a homologous dose-dependent desensitization. Moreover, in the absence of External Calcium, endothelin and PAF responses were smaller than carbachol response, although all three responses apparently resulted from release of Calcium ions from the same internal pool. In additional experiments, we observed that, like carbachol, endothelin and PAF contracted the parietal sheet, which is only composed of myoepithelial cells.(ABSTRACT TRUNCATED AT 250 WORDS)
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cholinergic effects on intracellular free Calcium concentration in renal corpuscle role of parietal sheet
American Journal of Physiology-renal Physiology, 1992Co-Authors: F. Lebrun, G Vassent, F. Morel, J MarchettiAbstract:: To investigate a possible effect of cholinergic agonists on the renal glomerular function, fura-2 microfluorometric measurements of intracellular free Calcium [( Ca2+]i) were performed on single intact glomeruli, single isolated parietal sheets of the Bowman's capsule and single parietal sheet-deprived glomeruli (PS-D glomerulus). Carbachol (10(-4) M), in the presence of 2 mM External Calcium, induced a biphasic increase in [Ca2+]i characterized by a sharp initial peak followed by a sustained plateau in the whole glomerulus (delta [Ca2+]i = 177 +/- 13 and 70 +/- 7 nM, respectively; n = 21) and in the parietal sheet (418 +/- 30 and 111 +/- 13 nM, respectively; n = 21). In the PS-D glomerulus (n = 9), the response was less marked and included a barely visible peak (77 +/- 13 nM) and a relatively low plateau (49 +/- 11 nM). In the absence of External Calcium, the peak phase was preserved in the three structures, indicating a Calcium release from intracellular pools, whereas the plateau, due to the entry of External Calcium, was suppressed. These effects were fully inhibited by 10(-4) M of either atropine or pirenzepine, demonstrating the muscarinic nature of the receptors. Dose-response curves showed that the parietal sheet was more sensitive to the physiological agonist (acetylcholine) than to carbachol. A still unexplained difference in sensitivity was noted between peak and plateau, respectively (half-maximal responses were 5 x 10(-6) vs. 5 x 10(-7) M for carbachol and 2 x 10(-7) vs. 3 x 10(-8) M for acetylcholine).(ABSTRACT TRUNCATED AT 250 WORDS)
R M Rajerison - One of the best experts on this subject based on the ideXlab platform.
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the parietal sheet of bowman s capsule of rat renal glomerulus a target of endothelin and paf
American Journal of Physiology-renal Physiology, 1995Co-Authors: J Marchetti, F. Lebrun, P Meneton, May Blochfaure, R M RajerisonAbstract:On the basis of intracellular Calcium concentration ([Ca 2+ ] i ) measurements, we have previously reported that the parietal sheet of Bowman's capsule was sensitive to cholinergic agonists. The aim of the present work was to investigate whether this structure could be also a target of endothelin and platelet activating factor (PAF), since we observed [Ca 2+ ] i increases in response to both agonists in the glomerulus, but which were very different from that induced by carbachol. For this purpose, we measured [Ca 2+ ] i on single microdissected parietal sheets, using a fura 2 microfluorescence technique and compared the effects of maximal concentrations of the three agonists (10 −7 , 10 −8 , and 10 −4 M for endothelin, PAF, and carbachol, respectively) under various experimental conditions. We observed that, like in the glomerulus, endothelin and PAF induced, in the parietal sheet, [Ca 2+ ] i responses that differed in many respects from those found with carbachol. Thus, in the presence of 2 mM External Calcium, 1) endothelin and PAF responses spontaneously declined to basal level, whereas a stationary plateau was observed after a sharp peak of [Ca 2+ ] i with carbachol; 2) the magnitude of [Ca 2+ ] i peak was smaller with endothelin and PAF than with carbachol; and 3) endothelin and PAF, but not carbachol, induced a homologous dose-dependent desensitization. Moreover, in the absence of External Calcium, endothelin and PAF responses were smaller than carbachol response, although all three responses apparently resulted from release of Calcium ions from the same internal pool. In additional experiments, we observed that, like carbachol, endothelin and PAF contracted the parietal sheet, which is only composed of myoepithelial cells. In conclusion, three agonists, namely carbachol, endothelin, and PAF, are now known to act on the parietal sheet by increasing [Ca 2 ] i and inducing contractions
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The parietal sheet of Bowman's capsule of rat renal glomerulus: a target of endothelin and PAF.
The American journal of physiology, 1995Co-Authors: J Marchetti, F. Lebrun, P Meneton, M Bloch-faure, R M RajerisonAbstract:On the basis of intracellular Calcium concentration ([Ca2+]i) measurements, we have previously reported that the parietal sheet of Bowman's capsule was sensitive to cholinergic agonists. The aim of the present work was to investigate whether this structure could be also a target of endothelin and platelet-activating factor (PAF), since we observed [Ca2+]i increases in response to both agonists in the glomerulus, but which were very different from that induced by carbachol. For this purpose, we measured [Ca2+]i on single microdissected parietal sheets, using a fura 2 microfluorescence technique and compared the effects of maximal concentrations of the three agonists (10(-7), 10(-8), and 10(-4) M for endothelin, PAF, and carbachol, respectively) under various experimental conditions. We observed that, like in the glomerulus, endothelin and PAF induced, in the parietal sheet, [Ca2+]i responses that differed in many respects from those found with carbachol. Thus, in the presence of 2 mM External Calcium, 1) endothelin and PAF responses spontaneously declined to basal level, whereas a stationary plateau was observed after a sharp peak of [Ca2+]i with carbachol; 2) the magnitude of [Ca2+]i peak was smaller with endothelin and PAF than with carbachol; and 3) endothelin and PAF, but not carbachol, induced a homologous dose-dependent desensitization. Moreover, in the absence of External Calcium, endothelin and PAF responses were smaller than carbachol response, although all three responses apparently resulted from release of Calcium ions from the same internal pool. In additional experiments, we observed that, like carbachol, endothelin and PAF contracted the parietal sheet, which is only composed of myoepithelial cells.(ABSTRACT TRUNCATED AT 250 WORDS)
Eduardo Rojas - One of the best experts on this subject based on the ideXlab platform.
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Quantitative analysis of depolarization-induced ATP release from mouse brain synaptosomes: External Calcium dependent and independent processes
The Journal of Membrane Biology, 1992Co-Authors: Jenny L Fiedler, Harvey B Pollard, Eduardo RojasAbstract:We and others have shown previously that ATP is secreted from mouse brain synaptosomes following depolarization of the membrane by high [K^+]_ 0 and the time course can be monitored accurately by measuring the light emitted from luciferin-luciferase included in the reaction medium. In the present work we have evaluated the relative importance of [Ca^2+]_ 0 and membrane potential on the ATP secretion process by modelling the time course of ATP release under different conditions. After correction of the records for destruction of released ATP by synaptosomal ecto-ATPase activity, we found that ATP secretion occurs by an apparent first order process. We also established that, in addition to the classical [Ca^2+]_ 0 -dependent mode, ATP secretion also occurred in the absence of extracellular Calcium ([Ca^2+]_ 0 < 1 μ m ). Upon lowering the extracellular Ca^2+ concentration, both the rate and the extent of ATP secretion decreased. To assess the contribution of membrane potential to the release rate we measured ATP secretion at membrane potentials determined by extracellular [K^+]_ 0 (or [Rb^+]_ 0 ) as defined by the distribution of the carbocyanine dye, diSC_3(5). Rate constants computed from measured secretion curves revealed that this parameter was essentially independent of membrane potential in the absence of [Ca^2+]_ 0 . Noise analysis of the light signal showed that the variance increased upon stimulation by high [K^+]_ 0 , suggesting that both modes of secretion are quantal. Thus, we conclude that the rate of ATP secretion from nerve terminals depends upon Ca^2+ entry but not on membrane potential, per se
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quantitative analysis of depolarization induced atp release from mouse brain synaptosomes External Calcium dependent and independent processes
The Journal of Membrane Biology, 1992Co-Authors: Jenny L Fiedler, Harvey B Pollard, Eduardo RojasAbstract:We and others have shown previously that ATP is secreted from mouse brain synaptosomes following depolarization of the membrane by high [K+]o and the time course can be monitored accurately by measuring the light emitted from luciferin-luciferase included in the reaction medium. In the present work we have evaluated the relative importance of [Ca2+]o and membrane potential on the ATP secretion process by modelling the time course of ATP release under different conditions. After correction of the records for destruction of released ATP by synaptosomal ecto-ATPase activity, we found that ATP secretion occurs by an apparent first order process. We also established that, in addition to the classical [Ca2+]o-dependent mode, ATP secretion also occurred in the absence of extracellular Calcium ([Ca2+]o less than 1 microM). Upon lowering the extracellular Ca2+ concentration, both the rate and the extent of ATP secretion decreased. To assess the contribution of membrane potential to the release rate we measured ATP secretion at membrane potentials determined by extracellular [K+]o (or [Rb+]o) as defined by the distribution of the carbocyanine dye, diSC3(5). Rate constants computed from measured secretion curves revealed that this parameter was essentially independent of membrane potential in the absence of [Ca2+]o. Noise analysis of the light signal showed that the variance increased upon stimulation by high [K+]o, suggesting that both modes of secretion are quantal. Thus, we conclude that the rate of ATP secretion from nerve terminals depends upon Ca2+ entry but not on membrane potential, per se.
