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David F Chang - One of the best experts on this subject based on the ideXlab platform.
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the effect of α1 adrenergic receptor antagonist tamsulosin flomax on Iris Dilator smooth Muscle anatomy
Ophthalmology, 2010Co-Authors: Ricardo M Santaella, John J Destafeno, Sandra S Stinnett, Alan D Proia, David F ChangAbstract:Purpose To characterize and determine the effect of tamsulosin (Flomax) on the human Iris Dilator Muscle anatomy. Design Retrospective, case-control study. Participants This study comprised 51 cadaveric eyes from 27 patients (14 with a history of tamsulosin use and 13 control patients) who underwent autopsy at the Duke University Medical Center, Durham, North Carolina. Methods Patients' records were reviewed, and age, medical, surgical, and ocular history; gender; medications; and duration and dosage of tamsulosin were recorded. Specimens were sectioned through the pupillary axis in the horizontal meridian and reviewed by light microscopy. A morphometric analysis was performed to measure the maximum and minimum Iris Dilator Muscle thickness and the Iris stromal thickness (micrometers) at 6 points in each eye. All microscopic evaluations and measurements were performed by the same masked observer. Main Outcome Measures To determine whether there is a significant difference in the Iris Dilator Muscle or stromal thickness in those patients receiving tamsulosin treatment compared with age-matched controls. Results The mean Iris Dilator Muscle thickness in the tamsulosin-treated group (6.53±1.99 μm) was significantly thinner compared with that of the control group (8.50±1.61 μm) ( P= 0.006). There was no difference in Iris stromal thickness between the 2 groups ( P= 0.268). There was no direct relationship between duration of tamsulosin use and Iris Dilator Muscle or stromal thickness. Statistical significance was maintained when the Iris Dilator Muscle thickness was compared between the groups using history of diabetes and cataract extraction as separate variables. No difference was noted when comparing the Iris stromal thickness using diabetes as a separate variable. However, stromal thickness was significantly different between the groups in pseudophakic eyes ( P= 0.005). Conclusions According to histologic examination of cadaver eyes, patients receiving tamsulosin treatment exhibited decreased Iris Dilator Muscle thickness compared with control patients. There was no difference noted in the Iris stromal thickness within the groups. We believe this finding may shed light on the pathophysiology of intraoperative floppy Iris syndrome. Further studies need to be performed to assess the significance of this histologic finding. Financial Disclosure(s) No author has a financial or proprietary interest in any material or method mentioned.
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comparative effect of alfuzosin and tamsulosin on the contractile response of isolated rabbit prostatic and Iris Dilator smooth Muscles possible model for intraoperative floppy Iris syndrome
Journal of Cataract and Refractive Surgery, 2008Co-Authors: Stefano Palea, Moez Rekik, Alain Regnier, David F Chang, Philippe LluelAbstract:PURPOSE: To compare the pharmacologic properties of tamsulosin and alfuzosin in isolated prostatic and Iris Dilator smooth Muscle from pigmented rabbits. SETTING: UROsphere Laboratories, Universite Paul Sabatier, Toulouse, France. METHODS: Prostatic and Iris Dilator smooth Muscle strips were placed in organ baths. A concentration-response curve to phenylephrine was compared before and after incubation with tamsulosin or alfuzosin. RESULTS: Both drugs were approximately 30 times less potent in Iris Dilator than prostatic smooth Muscle. In the Iris, tamsulosin acted as a competitive antagonist starting at the 0.03 microM concentration (pA(2)=7.96). This is in the same range as the maximum plasma concentration after a 0.4 mg dose of tamsulosin in humans (0.025 microM). The antagonistic effect of alfuzosin in the Iris was weaker (calculated mean pA(2) value of 5.63+/-0.19). Concentrations with an equipotent antagonistic effect on rabbit Iris Dilator Muscle (3.0 and 10.0 microM) were approximately 100 to 300 times higher than the maximum plasma concentrations after a 10.0 mg dose of alfuzosin in humans (0.032 microM). CONCLUSIONS: Tamsulosin was more effective than alfuzosin at blocking adrenergic contraction of the Iris Dilator Muscle in pigmented rabbits. Both drugs were less potent in the Iris than in the prostate, which suggests that an additional Iris receptor could be involved. If valid in humans, our results suggest that attainable plasma concentrations of tamsulosin are able to antagonize Iris Dilator smooth Muscle contraction, whereas those of alfuzosin are not. This could explain the higher frequency of intraoperative floppy-Iris syndrome in patients treated with tamsulosin than with alfuzosin.
Philippe Lluel - One of the best experts on this subject based on the ideXlab platform.
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comparative effect of alfuzosin and tamsulosin on the contractile response of isolated rabbit prostatic and Iris Dilator smooth Muscles possible model for intraoperative floppy Iris syndrome
Journal of Cataract and Refractive Surgery, 2008Co-Authors: Stefano Palea, Moez Rekik, Alain Regnier, David F Chang, Philippe LluelAbstract:PURPOSE: To compare the pharmacologic properties of tamsulosin and alfuzosin in isolated prostatic and Iris Dilator smooth Muscle from pigmented rabbits. SETTING: UROsphere Laboratories, Universite Paul Sabatier, Toulouse, France. METHODS: Prostatic and Iris Dilator smooth Muscle strips were placed in organ baths. A concentration-response curve to phenylephrine was compared before and after incubation with tamsulosin or alfuzosin. RESULTS: Both drugs were approximately 30 times less potent in Iris Dilator than prostatic smooth Muscle. In the Iris, tamsulosin acted as a competitive antagonist starting at the 0.03 microM concentration (pA(2)=7.96). This is in the same range as the maximum plasma concentration after a 0.4 mg dose of tamsulosin in humans (0.025 microM). The antagonistic effect of alfuzosin in the Iris was weaker (calculated mean pA(2) value of 5.63+/-0.19). Concentrations with an equipotent antagonistic effect on rabbit Iris Dilator Muscle (3.0 and 10.0 microM) were approximately 100 to 300 times higher than the maximum plasma concentrations after a 10.0 mg dose of alfuzosin in humans (0.032 microM). CONCLUSIONS: Tamsulosin was more effective than alfuzosin at blocking adrenergic contraction of the Iris Dilator Muscle in pigmented rabbits. Both drugs were less potent in the Iris than in the prostate, which suggests that an additional Iris receptor could be involved. If valid in humans, our results suggest that attainable plasma concentrations of tamsulosin are able to antagonize Iris Dilator smooth Muscle contraction, whereas those of alfuzosin are not. This could explain the higher frequency of intraoperative floppy-Iris syndrome in patients treated with tamsulosin than with alfuzosin.
Ricardo M Santaella - One of the best experts on this subject based on the ideXlab platform.
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the effect of α1 adrenergic receptor antagonist tamsulosin flomax on Iris Dilator smooth Muscle anatomy
Ophthalmology, 2010Co-Authors: Ricardo M Santaella, John J Destafeno, Sandra S Stinnett, Alan D Proia, David F ChangAbstract:Purpose To characterize and determine the effect of tamsulosin (Flomax) on the human Iris Dilator Muscle anatomy. Design Retrospective, case-control study. Participants This study comprised 51 cadaveric eyes from 27 patients (14 with a history of tamsulosin use and 13 control patients) who underwent autopsy at the Duke University Medical Center, Durham, North Carolina. Methods Patients' records were reviewed, and age, medical, surgical, and ocular history; gender; medications; and duration and dosage of tamsulosin were recorded. Specimens were sectioned through the pupillary axis in the horizontal meridian and reviewed by light microscopy. A morphometric analysis was performed to measure the maximum and minimum Iris Dilator Muscle thickness and the Iris stromal thickness (micrometers) at 6 points in each eye. All microscopic evaluations and measurements were performed by the same masked observer. Main Outcome Measures To determine whether there is a significant difference in the Iris Dilator Muscle or stromal thickness in those patients receiving tamsulosin treatment compared with age-matched controls. Results The mean Iris Dilator Muscle thickness in the tamsulosin-treated group (6.53±1.99 μm) was significantly thinner compared with that of the control group (8.50±1.61 μm) ( P= 0.006). There was no difference in Iris stromal thickness between the 2 groups ( P= 0.268). There was no direct relationship between duration of tamsulosin use and Iris Dilator Muscle or stromal thickness. Statistical significance was maintained when the Iris Dilator Muscle thickness was compared between the groups using history of diabetes and cataract extraction as separate variables. No difference was noted when comparing the Iris stromal thickness using diabetes as a separate variable. However, stromal thickness was significantly different between the groups in pseudophakic eyes ( P= 0.005). Conclusions According to histologic examination of cadaver eyes, patients receiving tamsulosin treatment exhibited decreased Iris Dilator Muscle thickness compared with control patients. There was no difference noted in the Iris stromal thickness within the groups. We believe this finding may shed light on the pathophysiology of intraoperative floppy Iris syndrome. Further studies need to be performed to assess the significance of this histologic finding. Financial Disclosure(s) No author has a financial or proprietary interest in any material or method mentioned.
Watanabe M - One of the best experts on this subject based on the ideXlab platform.
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Characterization of muscarinic receptors mediating relaxation and contraction in the rat Iris Dilator Muscle.
1995Co-Authors: Masuda Y, Yamahara N S, Tanaka M, Ryang S, Kawai T, Imaizumi Y, Watanabe MAbstract:1. The characteristics of muscarinic receptors mediating relaxation and/or contraction in the rat Iris Dilator Muscle were examined. 2. Relaxation was induced in a Dilator Muscle by application of acetylcholine (ACh) at low doses (3 microM or less) and contraction was induced by high doses. Methacholine and carbachol also showed biphasic effects similar to those of ACh; in contrast, bethanechol, arecoline, pilocarpine and McN-A-343 induced mainly relaxation but no substantial contraction. 3. After parasympathetic denervation by ciliary ganglionectomy, the relaxant response to muscarinic agonists disappeared upon nerve stimulation. Application of McN-A-343 and pilocarpine induced only small contractions in denervated Dilator Muscles, indicating that these are partial agonists for contraction. 4. pA2 values of pirenzepine, methoctramine, AF-DX 116, himbacine, and 4-DAMP for antagonism to pilocarpine-induced relaxation in normal Dilator Muscles and those for antagonism to ACh-induced contraction in denervated Dilator Muscles were determined. The pA2 values for antagonism to relaxation of all these antagonists were most similar to those for M3-type muscarinic receptors. 5. Although pA2 values for contraction of these antagonists, except for methoctramine, were very close to those for relaxation, contraction was not significantly antagonized by methoctramine. Contraction might be mediated by M3-like receptors which have a very low affinity for methoctramine. 6. In conclusion, ACh-induced biphasic responses in rat Iris Dilator Muscles were clearly distinguished from each other by specific muscarinic agonists and parasympathetic denervation, whereas muscarinic receptors could not be subclassified according to the pA2 values of 5 specific antagonists only
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Pertussis toxin-sensitive muscarinic relaxation in the rat Iris Dilator Muscle.
1995Co-Authors: Yamahara N S, Tanaka M, Imaizumi Y, Watanabe MAbstract:1. The effects of pertussis toxin (PTX) on contraction and/or relaxation induced by agonists or transmural nerve stimulation (TNS) were examined in the rat Iris Dilator and sphincter Muscles. 2. TNS in the presence of phentolamine induced an atropine-sensitive biphasic response: initial contraction followed by relaxation in Dilator Muscles. Exogenously applied acetylcholine (ACh) elicited a large relaxation at low doses (3 microM or less) and a concentration at high doses. 3. Only the ACh-induced relaxation was affected by injection of PTX (10 ng) into the anterior eye chamber. Relaxation was decreased 12 h after injection and had completely disappeared after 24 h. Relaxation recovered in part 3 weeks and almost completely 8 weeks after PTX treatment. A gradual decrease in muscarinic relaxation in a Dilator Muscle was also observed in vitro after addition of PTX to the bathing solution. 4. The pA2 values of muscarinic blockers, pirenzepine, AF-DX 116, 4-DAMP, and himbacine for competitive antagonism to ACh-induced contraction were 7.14, 6.53, 9.03, and 6.80, respectively, in PTX-pretreated Dilator Muscles. These values are comparable to those obtained in parasympathectomized Dilator Muscles and may indicate involvement of M3 or M3-like receptors in Muscle contraction. 5. Pretreatment with PTX did not significantly affect contraction induced by noradrenaline or 5-hydroxytryptamine or the relaxation induced by isoprenaline in Dilator Muscles. 6. In conclusion, among several agonist-induced responses in the rat Iris Dilator and sphincter Muscles, only muscarinic relaxation in Dilator Muscle occurs via activation of PTX-sensitive GTP binding proteins
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Atropine-resistant relaxation induced by high K+ in Iris Dilator Muscle of the rat and pig.
2024Co-Authors: Ryang S, Kawai T, Imaizumi Y, Takei S., Watanabe MAbstract:1. The effects of high K+ ion concentration on the isometric tension in Dilator Muscle strips of the rat and porcine Iris were examined. A high K+ solution, prepared by the replacement of Na+ in the medium with equimolar K+, was applied in the presence of 1 microM phentolamine, 1 microM propranolol and 1 or 10 microM atropine. High K+ (greater than 20 mM) induced a biphasic response; an initial phasic contraction followed by relaxation rather than tonic contraction. 2. An additional application of a Ca2+ antagonist, 1 microM nifedipine or nicardipine, almost completely blocked the K(+)-induced initial contraction and enhanced the following relaxation. The effect of K+ under these conditions was concentration-dependent in the range 20 to 80 mM. The maximum amplitude of the atropine-resistant relaxation induced by high K+ corresponds to 50-75% of that produced by acetylcholine in the absence of atropine. A similar K(+)-induced relaxation was observed in the porcine Iris Dilator. 3. The atropine-resistant relaxation in the rat Iris Dilator was not affected by pretreatment with 10 microM ouabain. The relaxation induced by 40 or 80 mM K+ in the porcine Dilator was slightly enhanced or not affected, respectively, in the presence of 1 microM ouabain. Application of 10 microM ouabain per se induced relaxation in the porcine Iris Dilator. 4. The low Na+ ion concentration present in high K+ solutions was not responsible for the K(+)-induced relaxation since the complete replacement of Na in the medium with Tris did not affect significantly the relaxation produced by high K(+)-containing solutions.(ABSTRACT TRUNCATED AT 250 WORDS
Stefano Palea - One of the best experts on this subject based on the ideXlab platform.
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comparative effect of alfuzosin and tamsulosin on the contractile response of isolated rabbit prostatic and Iris Dilator smooth Muscles possible model for intraoperative floppy Iris syndrome
Journal of Cataract and Refractive Surgery, 2008Co-Authors: Stefano Palea, Moez Rekik, Alain Regnier, David F Chang, Philippe LluelAbstract:PURPOSE: To compare the pharmacologic properties of tamsulosin and alfuzosin in isolated prostatic and Iris Dilator smooth Muscle from pigmented rabbits. SETTING: UROsphere Laboratories, Universite Paul Sabatier, Toulouse, France. METHODS: Prostatic and Iris Dilator smooth Muscle strips were placed in organ baths. A concentration-response curve to phenylephrine was compared before and after incubation with tamsulosin or alfuzosin. RESULTS: Both drugs were approximately 30 times less potent in Iris Dilator than prostatic smooth Muscle. In the Iris, tamsulosin acted as a competitive antagonist starting at the 0.03 microM concentration (pA(2)=7.96). This is in the same range as the maximum plasma concentration after a 0.4 mg dose of tamsulosin in humans (0.025 microM). The antagonistic effect of alfuzosin in the Iris was weaker (calculated mean pA(2) value of 5.63+/-0.19). Concentrations with an equipotent antagonistic effect on rabbit Iris Dilator Muscle (3.0 and 10.0 microM) were approximately 100 to 300 times higher than the maximum plasma concentrations after a 10.0 mg dose of alfuzosin in humans (0.032 microM). CONCLUSIONS: Tamsulosin was more effective than alfuzosin at blocking adrenergic contraction of the Iris Dilator Muscle in pigmented rabbits. Both drugs were less potent in the Iris than in the prostate, which suggests that an additional Iris receptor could be involved. If valid in humans, our results suggest that attainable plasma concentrations of tamsulosin are able to antagonize Iris Dilator smooth Muscle contraction, whereas those of alfuzosin are not. This could explain the higher frequency of intraoperative floppy-Iris syndrome in patients treated with tamsulosin than with alfuzosin.
