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Merchant YP, Shetty SS, Shetty R. Comment on "Gland-sparing neck dissection: oncological and functional outcomes in oral cancer patients". Int J Oral Maxillofac Surg 2023; 52:1106-1107. [PMID: 36872217 DOI: 10.1016/j.ijom.2023.02.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2023] [Revised: 01/11/2023] [Accepted: 02/13/2023] [Indexed: 03/06/2023]
Affiliation(s)
- Y P Merchant
- Department of Oral and Maxillofacial Surgery, Dr. D. Y. Patil Dental College and Hospital, Dr. D. Y. Patil Vidyapeeth, Pimpri, Pune, Maharashtra, India.
| | - S S Shetty
- Department of Oral and Maxillofacial Surgery, Manipal College of Dental Sciences, Mangalore, A constituent unit of MAHE, Manipal, Karnataka, India.
| | - R Shetty
- Deparment of Head and Neck Surgical Oncology, ACTREC, TMC, Navi Mumbai, Maharashtra, India
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Sathish T, Oldenburg B, Thankappan KR, Absetz P, Shaw JE, Tapp RJ, Zimmet PZ, Balachandran S, Shetty SS, Aziz Z, Mahal A. Cost-effectiveness of a lifestyle intervention in high-risk individuals for diabetes in a low- and middle-income setting: Trial-based analysis of the Kerala Diabetes Prevention Program. BMC Med 2020; 18:251. [PMID: 32883279 PMCID: PMC7472582 DOI: 10.1186/s12916-020-01704-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/27/2020] [Accepted: 07/10/2020] [Indexed: 01/27/2023] Open
Abstract
BACKGROUND Data on the cost-effectiveness of lifestyle-based diabetes prevention programs are mostly from high-income countries, which cannot be extrapolated to low- and middle-income countries. We performed a trial-based cost-effectiveness analysis of a lifestyle intervention targeted at preventing diabetes in India. METHODS The Kerala Diabetes Prevention Program was a cluster-randomized controlled trial of 1007 individuals conducted in 60 polling areas (electoral divisions) in Kerala state. Participants (30-60 years) were those with a high diabetes risk score and without diabetes on an oral glucose tolerance test. The intervention group received a 12-month peer-support lifestyle intervention involving 15 group sessions delivered in community settings by trained lay peer leaders. There were also linked community activities to sustain behavior change. The control group received a booklet on lifestyle change. Costs were estimated from the health system and societal perspectives, with 2018 as the reference year. Effectiveness was measured in terms of the number of diabetes cases prevented and quality-adjusted life years (QALYs). Three times India's gross domestic product per capita (US$6108) was used as the cost-effectiveness threshold. The analyses were conducted with a 2-year time horizon. Costs and effects were discounted at 3% per annum. One-way and multi-way sensitivity analyses were performed. RESULTS Baseline characteristics were similar in the two study groups. Over 2 years, the intervention resulted in an incremental health system cost of US$2.0 (intervention group: US$303.6; control group: US$301.6), incremental societal cost of US$6.2 (intervention group: US$367.8; control group: US$361.5), absolute risk reduction of 2.1%, and incremental QALYs of 0.04 per person. From a health system perspective, the cost per diabetes case prevented was US$95.2, and the cost per QALY gained was US$50.0. From a societal perspective, the corresponding figures were US$295.1 and US$155.0. For the number of diabetes cases prevented, the probability for the intervention to be cost-effective was 84.0% and 83.1% from the health system and societal perspectives, respectively. The corresponding figures for QALY gained were 99.1% and 97.8%. The results were robust to discounting and sensitivity analyses. CONCLUSIONS A community-based peer-support lifestyle intervention was cost-effective in individuals at high risk of developing diabetes in India over 2 years. TRIAL REGISTRATION The trial was registered with Australia and New Zealand Clinical Trials Registry ( ACTRN12611000262909 ). Registered 10 March 2011.
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Affiliation(s)
- Thirunavukkarasu Sathish
- Melbourne School of Population and Global Health, University of Melbourne, Melbourne, Australia. .,Population Health Research Institute, McMaster University, 237 Barton Street East, Hamilton, L8L 2X2, ON, Canada.
| | - Brian Oldenburg
- Melbourne School of Population and Global Health, University of Melbourne, Melbourne, Australia.,WHO Collaborating Centre on Implementation Research for Prevention & Control of NCDs, University of Melbourne, Melbourne, Australia
| | - Kavumpurathu R Thankappan
- Achutha Menon Centre for Health Science Studies, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum, Kerala, India.,Department of Public Health and Community Medicine, Central University of Kerala, Kasaragod, Kerala, India
| | - Pilvikki Absetz
- Department of Public Health and Clinical Nutrition, University of Eastern Finland, Kuopio, Finland.,Faculty of Social Sciences, Tampere University, Tampere, Finland
| | | | - Robyn J Tapp
- Melbourne School of Population and Global Health, University of Melbourne, Melbourne, Australia.,School of Biomedical Engineering and Imaging Sciences, King's College London, London, UK.,Centre for Intelligent Healthcare, Faculty of Health and Life Sciences, Coventry University, Coventry, Australia
| | - Paul Z Zimmet
- Central Clinical School, Monash University, Melbourne, UK
| | - Sajitha Balachandran
- Achutha Menon Centre for Health Science Studies, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum, Kerala, India.,Population Research Centre, University of Kerala, Trivandrum, Kerala, India
| | - Suman S Shetty
- Melbourne School of Population and Global Health, University of Melbourne, Melbourne, Australia
| | - Zahra Aziz
- Melbourne School of Population and Global Health, University of Melbourne, Melbourne, Australia.,School of Psychological Sciences, Monash University, Melbourne, Kerala, Australia
| | - Ajay Mahal
- Melbourne School of Population and Global Health, University of Melbourne, Melbourne, Australia
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Aziz Z, Mathews E, Absetz P, Sathish T, Oldroyd J, Balachandran S, Shetty SS, Thankappan KR, Oldenburg B. A group-based lifestyle intervention for diabetes prevention in low- and middle-income country: implementation evaluation of the Kerala Diabetes Prevention Program. Implement Sci 2018; 13:97. [PMID: 30021592 PMCID: PMC6052531 DOI: 10.1186/s13012-018-0791-0] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2017] [Accepted: 07/03/2018] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND While several efficacy trials have demonstrated diabetes risk reduction through targeting key lifestyle behaviours, there is a significant evidence gap in relation to the successful implementation of such interventions in low- and middle-income countries (LMICs). This paper evaluates the implementation of a cluster randomised controlled trial of a group-based lifestyle intervention among individuals at high-risk of developing type 2 diabetes mellitus (T2DM) in the state of Kerala, India. Our aim is to uncover provider-, participant- and community-level factors salient to successful implementation and transferable to other LMICs. METHODS The 12-month intervention program consisted of (1) a group-based peer-support program consisting of 15 sessions over a period of 12 months for high-risk individuals, (2) peer leader (PL) training and ongoing support for intervention delivery, (3) diabetes education resource materials and (4) strategies to stimulate broader community engagement. The evaluation was informed by the RE-AIM and PIPE frameworks. RESULTS Provider-level factors: Twenty-nine (29/30, 97%) intervention groups organised all 15 sessions. A 2-day PL training was attended by 51(85%) of 60 PLs. The PL handbook was found to be 'very useful' by 78% of PLs. Participant-level factors: Of 1327 eligible individuals, 1007(76%) participants were enrolled. On average, participants attended eight sessions. Sixty-eight percent rated their interest in group sessions as 'very interested', and 55% found the group sessions 'very useful' in making lifestyle changes. Inconvenient time (43%) and location (21%) were found to be important barriers for participants who did not attend any sessions. Community-level factors: Community-based activities reached to 41% of the participants for walking groups, 40% for kitchen garden training, and 31% for yoga training. PLs were readily available for support outside the sessions, as 75% of participants reported extracurricular contacts with their PLs. The commitment from the local partner institute and political leaders facilitated the high uptake of the program. CONCLUSION A comprehensive evaluation of program implementation from the provider-, participant- and community-level perspectives demonstrates that the K-DPP program was feasible and acceptable in changing lifestyle behaviours in high-risk individuals. The findings from this evaluation will guide the future delivery of structured lifestyle modification diabetes programs in LMICs. TRIAL REGISTRATION Trial registration: Australia and New Zealand Clinical Trials Registry ACTRN12611000262909 . Registered 10 March 2011.
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Affiliation(s)
- Zahra Aziz
- Melbourne School of Population and Global Health, The University of Melbourne, Melbourne, Australia. .,Department of Epidemiology and Preventive Medicine, Monash University, Melbourne, Australia. .,WHO Collaborating Centre on Implementation Research for Prevention & Control of NCDs, Melbourne, Australia.
| | - Elezebeth Mathews
- Department of Public Health and Community Medicine, Central University of Kerala, Kasaragod, India
| | - Pilvikki Absetz
- School of Health Sciences, University of Tampere, Tampere, Finland.,Collaborative Care Systems Finland, Helsinki, Finland
| | - Thirunavukkarasu Sathish
- Melbourne School of Population and Global Health, The University of Melbourne, Melbourne, Australia.,Centre for Population Health Sciences, Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, Singapore
| | - John Oldroyd
- Department of Epidemiology and Preventive Medicine, Monash University, Melbourne, Australia
| | - Sajitha Balachandran
- Achutha Menon Centre for Health Science Studies, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Thiruvananthapuram, India
| | - Suman S Shetty
- Melbourne School of Population and Global Health, The University of Melbourne, Melbourne, Australia
| | - K R Thankappan
- Achutha Menon Centre for Health Science Studies, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Thiruvananthapuram, India
| | - Brian Oldenburg
- Melbourne School of Population and Global Health, The University of Melbourne, Melbourne, Australia.,Department of Epidemiology and Preventive Medicine, Monash University, Melbourne, Australia.,WHO Collaborating Centre on Implementation Research for Prevention & Control of NCDs, Melbourne, Australia
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Sharma S, Badbade P, Daniel B, Shetty SS, Sharma SK. Vein of Galen malformation. J Assoc Physicians India 2005; 53:865. [PMID: 16459529] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Affiliation(s)
- S Sharma
- Department of Medicine, Pad Dr D Y Patil Medical College, Pimpri, Pune
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Kukkola PJ, Bilci NA, Ikler T, Savage P, Shetty SS, DelGrande D, Jeng AY. Isoindolines: a new series of potent and selective endothelin-A receptor antagonists. Bioorg Med Chem Lett 2001; 11:1737-40. [PMID: 11425549 DOI: 10.1016/s0960-894x(01)00273-6] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
1,3-Disubstituted isoindolines have been discovered as a new class of potent functional ET(A) selective receptor antagonists through pharmacophore analysis of existing nonpeptide endothelin antagonists. The structure-activity relationships for both the trans and the cis series of isoindolines are discussed.
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Affiliation(s)
- P J Kukkola
- Metabolic and Cardiovascular Diseases, Novartis Institute for Biomedical Research, 07901, Summit NJ, USA.
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6
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Shetty SS, DelGrande D. Differential inhibition of the prejunctional actions of angiotensin II in rat atria by valsartan, irbesartan, eprosartan, and losartan. J Pharmacol Exp Ther 2000; 294:179-86. [PMID: 10871310] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/16/2023] Open
Abstract
The effects of valsartan and other nonpeptide angiotensin II type 1 (AT(1)) receptor blockers on the prejunctional actions of angiotensin II were investigated in the isolated left atria of rat. Norepinephrine stores in rat atria were loaded with [(3)H]norepinephrine, and neuronal norepinephrine release was deduced from the radioactivity efflux. Angiotensin II (10(-9) to 10(-6) M) produced concentration-dependent enhancement of the electrical stimulation-induced efflux of [(3)H]norepinephrine from the preparation. Pretreatment of tissues with valsartan, irbesartan, eprosartan, or losartan (10(-8) to 10(-6) M) produced concentration-dependent inhibitions of the stimulation-induced efflux of radioactivity observed in the presence of angiotensin II (10(-7) M). The AT(1) receptor blockers did not decrease the "basal stimulation-induced overflow of radioactivity but rather selectively inhibited the angiotensin II-mediated augmentation of the response. Regression analyses of the inhibition of the angiotensin II-mediated response by valsartan, irbesartan, eprosartan, and losartan revealed corresponding log IC(50) values (log M, with 95% confidence intervals) of -7.78 (-8.19, -7.51), -7.65 (-8.02, -7.40), -7.12 (-7. 37, -6.86), and -6.75 (-7.00, -6.40), indicating that the IC(50) values for valsartan and irbesartan are significantly lower than those for eprosartan and losartan. Thus, valsartan is a potent inhibitor of the prejunctional facilitatory effect of angiotensin II on the release of norepinephrine from peripheral sympathetic nerves. This implies that the therapeutic domain of valsartan may be extended to include pathophysiological conditions such as congestive heart failure wherein prejunctional angiotensin II receptors apparently play a significant role. Whether the high potency of valsartan translates into a significant clinical advantage relative to the other agents tested remains to be ascertained.
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Affiliation(s)
- S S Shetty
- Novartis Institute for Biomedical Research, Metabolic and Cardiovascular Diseases, Summit, New Jersey 07901-1027, USA.
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Bebernitz GR, Aicher TD, Stanton JL, Gao J, Shetty SS, Knorr DC, Strohschein RJ, Tan J, Brand LJ, Liu C, Wang WH, Vinluan CC, Kaplan EL, Dragland CJ, DelGrande D, Islam A, Lozito RJ, Liu X, Maniara WM, Mann WR. Anilides of (R)-trifluoro-2-hydroxy-2-methylpropionic acid as inhibitors of pyruvate dehydrogenase kinase. J Med Chem 2000; 43:2248-57. [PMID: 10841803 DOI: 10.1021/jm0000923] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The optimization of a series of anilide derivatives of (R)-3,3, 3-trifluoro-2-hydroxy-2-methylpropionic acid as inhibitors of pyruvate dehydrogenase kinase (PDHK) is described that started from N-phenyl-3,3,3-trifluoro-2-hydroxy-2-methylpropanamide 1 (IC(50) = 35 +/- 1.4 microM). It was found that small electron-withdrawing groups on the ortho position of the anilide, i.e., chloro, acetyl, or bromo, increased potency 20-40-fold. The oral bioavailability of the compounds in this series is optimal (as measured by AUC) when the anilide is substituted at the 4-position with an electron-withdrawing group (i.e., carboxyl, carboxyamide, and sulfoxyamide). N-(2-Chloro-4-isobutylsulfamoylphenyl)-(R)-3,3, 3-trifluoro-2-hydroxy-2-methylpropionamide (10a) inhibits PDHK in the primary enzymatic assay with an IC(50) of 13 +/- 1.5 nM, enhances the oxidation of [(14)C]lactate into (14)CO(2) in human fibroblasts, lowers blood lactate levels significantly 2.5 and 5 h after oral doses as low as 30 micromol/kg, and increases the ex vivo activity of PDH in muscle, kidney, liver, and heart tissues. However, in contrast to sodium dichloroacetate (DCA), these PDHK inhibitors did not lower blood glucose levels. Nevertheless, they are effective at increasing the utilization and disposal of lactate and could be of utility to ameliorate conditions of inappropriate blood lactate elevation.
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Affiliation(s)
- G R Bebernitz
- Metabolic and Cardiovascular Disease Research, Novartis Institute for Biomedical Research, Summit, New Jersey 07901, USA.
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8
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Aicher TD, Anderson RC, Gao J, Shetty SS, Coppola GM, Stanton JL, Knorr DC, Sperbeck DM, Brand LJ, Vinluan CC, Kaplan EL, Dragland CJ, Tomaselli HC, Islam A, Lozito RJ, Liu X, Maniara WM, Fillers WS, DelGrande D, Walter RE, Mann WR. Secondary amides of (R)-3,3,3-trifluoro-2-hydroxy-2-methylpropionic acid as inhibitors of pyruvate dehydrogenase kinase. J Med Chem 2000; 43:236-49. [PMID: 10649979 DOI: 10.1021/jm990358+] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
N'-methyl-N-(4-tert-butyl-1,2,5,6-tetrahydropyridine)thiourea, SDZ048-619 (1), is a modest inhibitor (IC(50) = 180 microM) of pyruvate dehydrogenase kinase (PDHK). In an optimization of the N-methylcarbothioamide moiety of 1, it was discovered that amides with a small acyl group, in particular appropriately substituted amides of (R)-3,3,3-trifluoro-2-hydroxy-2-methylpropionic acid, are inhibitors of PDHK. Utilizing this acyl moiety, herein is reported the rationale leading to the optimization of a series of acylated piperazine derivatives. Methyl substitution of the piperazine at the 2- and 5-positions (with S and R absolute stereochemistry) markedly increased the potency of the lead compound (>1,000-fold). Oral bioavailability of the compounds in this series is good and is optimal (as measured by AUC) when the 4-position of the piperazine is substituted with an electron-poor benzoyl moiety. (+)-1-N-[2,5-(S, R)-Dimethyl-4-N-(4-cyanobenzoyl)piperazine]-(R)-3,3, 3-trifluoro-2-hydroxy-2-methylpropanamide (14e) inhibits PDHK in the primary enzymatic assay with an IC(50) of 16 +/- 2 nM, enhances the oxidation of [(14)C]lactate into (14)CO(2) in human fibroblasts with an EC(50) of 57 +/- 13 nM, diminishes lactate significantly 2.5 h post-oral-dose at doses as low as 1 micromol/kg, and increases the ex vivo activity of PDH in muscle, liver, and fat tissues in normal Sprague-Dawley rats. These PDHK inhibitors, however, do not lower glucose in diabetic animal models.
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Affiliation(s)
- T D Aicher
- Novartis Institute for Biomedical Research, 556 Morris Avenue, Summit, New Jersey 07901, USA.
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Aicher TD, Damon RE, Koletar J, Vinluan CC, Brand LJ, Gao J, Shetty SS, Kaplan EL, Mann WR. Triterpene and diterpene inhibitors of pyruvate dehydrogenase kinase (PDK). Bioorg Med Chem Lett 1999; 9:2223-8. [PMID: 10465550 DOI: 10.1016/s0960-894x(99)00380-7] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Several oximes of triterpenes with a 17-beta hydroxyl and abietane derivatives are inhibitors of pyruvate dehydrogenase kinase (PDK) activity. The oxime 12 and dehydroabietyl amine 2 exhibit a blood glucose lowering effect in the diabetic ob/ob mouse after a single oral dose of 100 micromol/kg. However, the mechanism of the blood glucose lowering effect is likely unrelated to PDK inhibition.
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Affiliation(s)
- T D Aicher
- Metabolic & Cardiovascular Diesases Research, Novartis Institute for Biomedical Research, Summit, NJ 07901, USA
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10
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Aicher TD, Anderson RC, Bebernitz GR, Coppola GM, Jewell CF, Knorr DC, Liu C, Sperbeck DM, Brand LJ, Strohschein RJ, Gao J, Vinluan CC, Shetty SS, Dragland C, Kaplan EL, DelGrande D, Islam A, Liu X, Lozito RJ, Maniara WM, Walter RE, Mann WR. (R)-3,3,3-Trifluoro-2-hydroxy-2-methylpropionamides are orally active inhibitors of pyruvate dehydrogenase kinase. J Med Chem 1999; 42:2741-6. [PMID: 10425084 DOI: 10.1021/jm9902584] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- T D Aicher
- Novartis Institute for Biomedical Research, 556 Morris Avenue, Summit, New Jersey 07901, USA.
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11
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Shetty SS, Savage P, DelGrande D, De Lombaert S, Jeng AY. Characterization of CGS 31447, a potent and nonpeptidic endothelin-converting enzyme inhibitor. J Cardiovasc Pharmacol 1998; 31 Suppl 1:S68-70. [PMID: 9595403 DOI: 10.1097/00005344-199800001-00022] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Optimization of an aminophosphonic acid series of compounds for inhibition of endothelin-converting enzyme (ECE) has led to the discovery of CGS 31447. This compound reversibly inhibited the activity of recombinant human ECE-1 with an IC50 value of 21 nM. The effect of CGS 31447 was not due to nonspecific chelation of the zinc ion at the catalytic center of ECE-1 by the phosphonic acid of the inhibitor. Determination of kinetic parameters of ECE-1 in the presence of 5-15 nM CGS 31447 revealed the competitive nature of the compound; a K1 of 7 nM was obtained. CGS 31447 infused at concentrations of 0.01, 0.1, and 1.0 microM inhibited the mean increase in big ET-1-induced pressor responses in isolated and perfused rat kidneys by 7, 39, and 68%, respectively, compared with the controls. These results demonstrate that CGS 31447 is a potent, reversible, and competitive inhibitor of ECE-1.
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Affiliation(s)
- S S Shetty
- Research Department, Novartis Pharmaceuticals Corporation, Summit, NJ 07901, USA
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12
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Abstract
We evaluated the effects of endothelin-1 (ET-1) and prostaglandin F2alpha (PGF2alpha) selectively on conduit coronary artery diameter using a novel approach in which the local concentration of vasoactive agent was controlled and maintained in vivo. ET-1 and PGF2alpha were applied topically (100 microl every 3 min) to the external surface of the left circumflex coronary artery (LCx) in anesthetized dogs or to the bathing medium of isolated canine LCx rings in parallel in vitro experiments. The dose-dependent constrictions obtained in vivo and in vitro were similar with each agent. Single, approximately maximally effective concentrations of PGF2alpha evoked an initial rapid contraction followed by a slow and sustained larger contraction in both preparations. In contrast, single concentrations of ET-1 elicited a rapid constriction that partially recovered (50-80%) in the ensuing 1.5-2 h despite continuous exposure to ET-1. After the ET-1 constriction reversed, PGF2alpha could still elicit a contraction, indicating a homologous endothelin receptor desensitization. Both agents maximally decreased conduit artery cross-sectional area in vivo by approximately 40% without significantly changing LCx resistance. Thus this in situ technique revealed effects of ET-1 and PGF2alpha on a localized segment of coronary artery that were not discernible with either intravenous or intracoronary administration.
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Affiliation(s)
- D F Rigel
- Research Department, Pharmaceuticals Division, Ciba-Geigy Corporation, Summit, New Jersey 07901, USA
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13
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Webb RL, Hu S, Sills MA, Bazil MK, Cioffi CL, Shetty SS, Lappe RW, Rigel DF. In vitro and in vivo evaluation of an endothelin inhibitor reveals novel K+ channel opening activity. Biochem Biophys Res Commun 1996; 227:176-81. [PMID: 8858121 DOI: 10.1006/bbrc.1996.1485] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
A low molecular weight endothelin (ET-1) inhibitor (Ex. 127, European Patent Application 404 525 A2, Takeda Chemical Ind., 1991), CGS 26061, was synthesized and evaluated to determine its mechanism of action. CGS 26061 (10 microM) failed to inhibit binding of [125I]ET-1 in porcine thoracic aorta and was without effect on ET-1-induced [3H]inositol phosphate accumulation in A7r5 cells. However, CGS 26061 relaxed porcine coronary arterial rings precontracted with ET-1. In addition, contractions to PGF2 alpha and low K+ (20 mM) but not high K+ were attenuated, suggesting that CGS 26061 (1, 10 microM) is a potassium channel opener. Patch-clamp experiments confirmed the K+ channel activity (0.1-10 microM). The originally re ported inhibition of ET-1-induced pressor responses by Ex. 127 (CGS 26061) was not replicated in the anesthetized dog or conscious rat nor was it shown to be antihypertensive in SHR. These data have identified CGS 26061 as a novel K+ channel opener with a unique cardiovascular profile.
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Affiliation(s)
- R L Webb
- Research Department, Ciba-Geigy Corporation, Summit, New Jersey 07901, USA
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14
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Chin MH, Cioffi CL, Garay M, Neale RF, Shetty SS, DelGrande D, Mugrage B, Sills MA, Lipson KE. The unusual binding properties of the endothelin receptor antagonist CGS 27830 distinguishes receptor/agonist interactions. J Pharmacol Exp Ther 1996; 276:74-83. [PMID: 8558459] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
CGS 27830 [meso-1,4-dihydro-5-methoxycarbonyl-2,6-dimethyl-4-(3- nitrophenyl)-3-pyridine carboxylic acid anhydride] is a nonpeptidic, insurmountable, endothelin (ET) receptor antagonist with approximately 10- to 20-fold selectivity for ETA receptors. CGS 27830 exhibits unusual binding properties which depend on the receptor and ligand: standard saturation binding experiments (coincubation of membranes with ligand in the absence or presence of antagonist) suggest that CGS 27830 is a competitive inhibitor of [125I]IRL 1620 binding to ETB receptors in rat cerebellar membranes (i.e., there was a change of apparent Kd with no change of maximum binding), but a noncompetitive inhibitor of [125I]IRL 1620 binding to ETB receptors in rat lung membranes (i.e., significant loss of total binding was observed). Although the antagonist appears to be a noncompetitive inhibitor of [125I]IRL 1620 binding to ETB receptors in rat lung membranes, CGS 27830 appears to be a competitive inhibitor of [125I]ET-1 binding to the same receptors as well as to ETA receptors in A7r5 cell membranes. Thus, CGS 27830 can distinguish [125I]IRL 1620 binding to ETB receptors in rat cerebellar and lung membranes, but not ET-1 binding to ETB receptors in these tissues. These unusual binding properties demonstrate that rat lung and cerebellum ETB receptors interact differently with IRL 1620 or ET-1.
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Affiliation(s)
- M H Chin
- Ciba-Geigy Corporation, Research Department, Summit, New Jersey, USA
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Shetty SS, DelGrande D. Inhibition by nickel of endothelin-1-induced tension and associated 45Ca movements in rabbit aorta. J Pharmacol Exp Ther 1994; 271:1223-7. [PMID: 7996430] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Contractions induced by 10 nM endothelin-1 (ET) in the rabbit aortic media intimal layer were inhibited by prior exposure to 100 microM Ni++ (33.1%) or to a Ca(++)-free buffer (80.2%) but were unaffected by pretreatment with 0.1 microM nifedipine. Contractions elicited by phenylephrine (1 nM-100 microM) or K+ (10-50 mM) were not inhibited by 100 microM Ni++ but those induced by ET in tissues submaximally precontracted with 20 mM K+ were selectively antagonized by the divalent cation. The mechanism for the inhibitory action of Ni++ was ascertained by an examination of the effects of the cation on ET-induced alterations in the cellular distribution and mobilization of Ca++. Efflux of 45Ca from the muscle into a solution without added Ca++ was not altered by ET. Total or cellular 45Ca uptake (uptake after exposure to La and low temperature), at either low- or high-affinity sites in resting muscles was also not affected by the peptide. However, low-affinity cellular 45Ca retention in muscles depolarized with high K+ levels (160 mM) was significantly enhanced (45.1%) by ET. Ni++ did not alter 45Ca retention in control and K(+)-treated muscles but it blocked the additional incremental 45Ca uptake associated with ET (in the presence of high K+). Thus, Ni++ produced a selective blockade of an ET-activated Ca++ influx pathway, distinct from the dihydropyridine-sensitive L-type Ca++ channels, in rabbit aortic smooth muscle. This action by Ni++ apparently inhibits subsequent contractile responses of the muscle to ET.
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Affiliation(s)
- S S Shetty
- Research Department, Ciba-Geigy Corporation, Summit, New Jersey
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16
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Abstract
The ability of cathepsin D, chymosin, pepsin and renin to produce endothelin-1 (ET-1) from proendothelin-1 (proET-1) was compared. No significant conversion was observed when proET-1 was incubated with up to 1 U of renin for 15 min at 37 degrees C. Cathepsin D generated, as well as degraded, ET-1 rapidly. Net production of ET-1 reached a maximum when 0.003 U of cathepsin D was used, and about 16% of the initial proET-1 was detected as ET-1 by HPLC. Pepsin up to 1 U converted proET-1 into ET-1 dose-dependently with a maximum of 71% conversion. A further increase of the amount of pepsin in the reaction mixture produced nonspecific cleavage of ET-1. Less than 10% of ET-1 remained in the presence of 15 U of pepsin. Chymosin also generated ET-1 dose-dependently, and a complete conversion was obtained at 1 U of enzyme. Greater than 1 U of chymosin only slightly degraded ET-1; at least 80% of ET-1 was still present when 15 U of chymosin was included in the assay. Other properties associated with the conversion of proET-1 into ET-1 by chymosin were investigated. Similar to authentic ET-1, the product of chymosin treatment caused contraction of isolated rabbit aortic rings, and pre-incubation of chymosin with pepstatin A abolished this contractile response.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- P Savage
- Research Department, CIBA-GEIGY Corporation, Summit, New Jersey
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17
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Shetty SS, Okada T, Webb RL, DelGrande D, Lappe RW. Functionally distinct endothelin B receptors in vascular endothelium and smooth muscle. Biochem Biophys Res Commun 1993; 191:459-64. [PMID: 8461004 DOI: 10.1006/bbrc.1993.1240] [Citation(s) in RCA: 115] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
IRL 1620 (Suc-[Glu9,Ala11,15]-ET-1 (8-21)) (0.1 nM - 1 microM), a novel ETB-selective endothelin (ET) agonist, produced endothelium-dependent relaxations in precontracted rabbit mesenteric artery (2 nM, EC50) and endothelium-independent contractions in porcine coronary artery (18 nM, EC50). ET-3 (0.1 nM-10 nM) produced qualitatively similar responses in the two tissues. The maximal contractions induced by IRL 1620 or ET-3 were substantially smaller (< 20%) than that produced by ET-1. BQ-123 (1 microM), an ETA receptor antagonist, inhibited responses to ET-1 without affecting IRL 1620- or ET-3-induced responses in either tissue. Thus functionally distinct ETB receptors mediating vasodilator and vasoconstrictor effects are located on the vascular endothelium and smooth muscle, respectively. The overall effect of ETB receptor activation on vascular tone is tissue-specific and presumably reflects differing receptor distribution at the two sites.
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Affiliation(s)
- S S Shetty
- Research Department, Pharmaceuticals Division, CIBA-GEIGY Corp., Summit, NJ 07901
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18
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Knap AK, Soriano A, Savage P, Del Grande D, Shetty SS. Identification of a novel aspartyl endothelin converting enzyme in porcine aortic endothelial cells. Biochem Mol Biol Int 1993; 29:739-45. [PMID: 8490580] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
An enzyme which catalyzes the conversion of proendothelin-1 to the potent vasoconstrictor peptide endothelin-1 has been identified in the detergent extract of primary porcine aortic endothelial cell membranes. Partial purification was accomplished by anion exchange and Con A affinity chromatography. The enzyme was active at pH 4 and was inhibited by 100 nM peptstatin A. Hydrolysis products of proendothelin-1 were characterized by bioassay, RIA, HPLC and molecular mass analysis. Comparisons to cathepsin D and renin demonstrated that the endothelin converting enzyme activity from the porcine aortic endothelial cells was unrelated to the known enzymes. These results suggest that the processing of proendothelin-1 by endothelial cells involves a novel pepstatin-sensitive aspartyl protease.
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Affiliation(s)
- A K Knap
- Research Department, Ciba-Geigy Corp., Summit, NJ 07901
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19
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Deng Y, Savage P, Shetty SS, Martin LL, Jeng AY. Identification and partial purification of a thiol endothelin-converting enzyme from porcine aortic endothelial cells. J Biochem 1992; 111:346-51. [PMID: 1587796 DOI: 10.1093/oxfordjournals.jbchem.a123760] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Endothelin is a potent peptide vasoconstrictor. The final step in the processing of endothelin has been postulated to be the cleavage of the Trp21-Val22 peptide bond in proendothelin by a putative endothelin-converting enzyme. A soluble extract of primary porcine aortic endothelial cells was found to contain an enzyme activity that converted proendothelin-1 (proET-1) to an endothelin-1 (ET-1)-like peptide as determined by the rabbit aortic ring contraction assay. This enzyme was partially purified by DE52 ion-exchange chromatography. Incubation of proET-1 with the partially purified enzyme generated a product which had a retention time on HPLC identical to that of authentic ET-1. Further analysis of the product showed that it caused contraction of rabbit aortic rings, had a molecular weight identical to ET-1 as measured by fast atom bombardment mass spectrometry, and competed for [125I]ET-1 binding in an RIA using specific antibodies which recognize the carboxy terminal tryptophan of ET-1. The enzyme activity could be inhibited by thiol protease inhibitors such as Z-phe-pheCHN2 and p-hydroxymercuribenzoate, but not by serine- or metalloprotease inhibitors. The optimal pH for the enzymatic activity was between 7.0 and 7.5, and no activity was detected at pH 4.0. These results demonstrate that this thiol protease is a potential endothelin-converting enzyme.
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Affiliation(s)
- Y Deng
- Pharmaceuticals Division, CIBA-GEIGY Corp., Summit, NJ 07901
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20
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Shetty SS, Zawadzki JV, Weiss GB. Cellular Mg++ accumulation is altered by extracellular Na+ and directly affects agonist-induced mobilization of Ca++ in vascular smooth muscle. Adv Exp Med Biol 1992; 311:31-40. [PMID: 1529761 DOI: 10.1007/978-1-4615-3362-7_3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Effects of altered Na+, Ca++ and Mg++ concentrations on 45Ca and 28Mg distribution and binding as well as of changes in cellular Mg++ on mobilization of Ca++ by added norepinephrine (NE) were examined in the rabbit aortic media-intimal layer. Uptake of 45Ca at cellular high affinity sites was decreased by Mg++ much more than 28Mg uptake was altered by Ca++. Substitution of Na+ affects 45Ca uptake primarily at extracellular (La( )-accessible) binding sites. Muscles were pre-loaded with Mg++ by incubation in a low-Na+ solution (75% Na+ replaced isosmotically with sucrose) for 30 min followed by a 90 min exposure to a similar solution also containing 15 mM MgCl2. These tissues, upon examination in normal (154 mM) Na(+)-containing solution, indicated decreased retention of that cellular, high-affinity Ca++ fraction important for NE-induced contractile response. Accordingly, release of 45Ca from this site and associated tension responses to added NE were attenuated in these muscles. These results suggest that variations in extracellular Na+ concentration modulate binding and subsequent mobilization of activator Ca++ by agonists through alterations in cellular Mg++ content in vascular smooth muscle.
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Affiliation(s)
- S S Shetty
- CIBA-GEIGY Corporation, Research Department, Summit, NJ 07901
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21
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Shetty SS, Weiss GB. Effects of pH and anion substitution on magnesium accumulation in rabbit aortic smooth muscle. Blood Vessels 1989; 26:65-76. [PMID: 2758108 DOI: 10.1159/000158755] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The effects of anion substitution, pH and extracellular Mg2+ concentration on 28Mg accumulation were examined in rabbit aortic smooth muscle. Accumulation of 28Mg (expressed as a 28Mg/Mg2+ ratio) was not changed when the concentration of added, nonradioactive MgCl2 was increased from 1.5 to 15.0 mM. The 28Mg efflux rate was increased by added MgCl2 (0.15, 0.5 or 1.5 mM) in a dose-related manner after a similar delay of 5-10 min. Addition of 1.5 mM MgCl2, MgSO4 or magnesium aspartate hydrochloride enhanced 28Mg efflux and inhibited accumulation of 28Mg to the same extent. An increase or decrease in extracellular pH correspondingly increased or decreased 28Mg accumulation. However, the 28Mg efflux rate was not altered when extracellular pH was decreased. Efflux of 28Mg was increased by added 1.5 mM MgCl2 at pH 7.4 but not at pH 5.8. Thus, the net uptake of Mg2+ appears to be proportional to the concentration of extracellular Mg2+ in rabbit aorta. Low external pH decreases 28Mg retention in rabbit aorta by inhibiting the uptake of 28Mg rather than by increasing 28Mg efflux. Effects of added Mg2+ on transmembrane movements of 28Mg are not altered by changes in the associated anion. Extracellular Mg2+ appears to enter the cell and exchange with an intracellularly located pool of 28Mg in the same manner, regardless of whether the accompanying anion is sulfate, chloride or monoaspartate hydrochloride.
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Affiliation(s)
- S S Shetty
- Research Department, Ciba-Geigy Corporation, Summit, N.J
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22
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Shetty SS, Weiss GB. Alterations in 28Mg distribution and movements in rabbit aortic smooth muscle. J Pharmacol Exp Ther 1988; 245:112-9. [PMID: 3129548] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
The distribution and transmembrane fluxes of 28Mg were examined in the isolated media-intimal layer of rabbit aorta. Accumulation of 28Mg was slow and not complete after a 3-hr incubation. The major portion of the cellular Mg++ is not exchangeable. The 28Mg efflux rate was increased by 1.5 mM nonradioactive Mg++ after a time lag of 5 to 10 min; this increase was blocked reversibly by decreasing bathing solution temperature to 4 degrees C. A rapid and sustained increase in 28Mg efflux rate was elicited with added EDTA. Accumulation of 28Mg by rabbit aorta was increased more than 5-fold by substituting sucrose for NaCl in the bathing solution. Q10 values obtained for Mg++ accumulation in rabbit aorta incubated at different temperatures either in normal solution or low-Na+ solution ranged from 1.3 to 2.0. Uptake of 28Mg was inhibited substantially by 60 mM added K+, 1.5 or 15.0 mM La , 7 mM neomycin or 1 microgram/ml of antimycin A. These ions and drugs did not significantly increase 28Mg efflux when added during the slow component phase of the washout. Thus, the major portion of slowly accumulated Mg++ appears to be stored and exchanged intracellularly. The transmembrane movements of Mg++ depend upon simple diffusion, Mg++-Mg++ exchange and a transport process that is increased when Na+ is decreased. The EDTA-induced increase in 28Mg efflux rate may result from nonspecific membrane permeability increases, whereas ions and drugs decrease cellular Mg++ content by reducing uptake rather than increasing loss.
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Affiliation(s)
- S S Shetty
- Research Department, Ciba-Geigy Corporation, Summit, New Jersey
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Shetty SS, Weiss GB. Specific actions of gallium on norepinephrine-induced tension and associated 45Ca movements in rabbit aortic smooth muscle. J Pharmacol Exp Ther 1987; 243:614-7. [PMID: 3681698] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Gallium ion (Ga) dose-dependently (60-360 microM) inhibited contractions induced by norepinephrine (NE, 1 microM) in rabbit aortic (and media intimal) strips, but did not affect contractions elicited with high K+ (80 mM) solution. The initial phasic portion of the NE-induced response was either unaffected or only slightly (less than 10%) reduced, but the tonic portion of the response was inhibited completely by higher concentrations (greater than or equal to 300 microM) of Ga . In resting muscles, the equilibrated (90 min) 45Ca uptake was not altered by Ga (360 microM). Also, 45Ca efflux from either high- or low-affinity Ca++ binding sites was unaltered by Ga . The effects of Ga (360 microM) on 45Ca retained after a subsequent 60-min washout at 0.5 degrees C in an isosmotic (80.8 mM) La solution were also examined. High affinity La -resistant 45Ca released by NE (1 microM) was not altered by Ga . Under conditions favoring low affinity Ca++ uptake, 45Ca retention in control and K+-treated muscles was not changed by Ga , but the additional incremental 45Ca uptake associated with NE (in the presence of high K+) was blocked. Thus, Ga appears to have a selective inhibitory action on NE-associated 45Ca uptake without affecting either resting and high K+-induced 45Ca uptake or that 45Ca fraction released by NE. This action may result from a selective blockade by Ga of receptor-linked Ca++ channels in rabbit aortic smooth muscle.
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Affiliation(s)
- S S Shetty
- Research Department, CIBA-GEIGY Corporation, Summit, New Jersey
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Abstract
In rat portal vein, 0.5 and 5.0 microM BRL 34915 [(+/-)-6-cyano-3,4-dihydro-2,2-dimethyl-trans-4-(2-oxo-1-pyrrolidyl++ +)-2H- benzo[b]pyran-3-ol] abolished spontaneous rhythmic movements and norepinephrine (NE)-induced tension responses, respectively. Only the higher (5 microM) concentration of BRL 34915 increased 42K efflux and inhibited the NE-induced increase in 42K efflux. These results suggest that BRL 34915 inhibits spontaneous rhythmic movements and NE-induced tension responses by differing mechanisms of action and that only the block of the NE-induced tension response is related to K+ permeability or conductance changes.
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Affiliation(s)
- S S Shetty
- Research Department, Ciba-Geigy Corporation, Summit, NJ 07901
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Abstract
TMB-8 [8-(diethylamino)-octyl-3,4,5-trimethoxybenzoate] is known to inhibit calcium ion dependent processes in several tissues by stabilizing some intracellular stores of membrane-bound calcium. TMB-8 was used to study the excitation-contraction (E-C) coupling process in frog's skeletal muscle. TMB-8 (5 X 10(-5) - 10(-4) M) blocked electrically evoked twitches but not high K+ (123 mM)- or caffeine (2.36 mM)-induced contractures in isolated, curarized toe muscles. TMB-8 (10(-4) M) produced a small decrease (16%) in the action potential of frog's sartorius muscle fibres. However, reducing extracellular Na+ to 44.7 mM produced a similar reduction (17%) in action potential amplitude but did not suppress the twitch; i.e. it produced only a small increase (about 10%) in twitch amplitude. It is known that potassium contractures are produced by extracellular Ca++ ions which enter through calcium channels in the t-tubules and that caffeine produces contractures by sensitizing the sarcoplasmic reticulum to Ca++-induced Ca++ release. The present results suggest that TMB-8 blocks twitches by preventing the release of Ca++ ions bound to the intracellular surface of the t-tubular membrane which is often called the store of 'trigger-calcium' ions.
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Shetty SS, Frank GB. Mechanism for the opioid-induced twitch potentiations of frog's skeletal muscle. Can J Physiol Pharmacol 1986; 64:983-92. [PMID: 3490300 DOI: 10.1139/y86-168] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The twitch-potentiating effects of opioids in the frog's skeletal muscle which are naloxone resistant and nonstereospecific were further studied. The rapid kinetics of the onset and of the offset (following washout) of the opioid effect indicates that the site for this action is the surface membrane of the muscle fibre. On the other hand, the lack of any twitch-potentiating effect by naloxone methylbromide, a quaternary derivative of naloxone, suggests that opioids which potentiate the twitch must enter the lipid phase of the membrane to act. Intracellular microelectrode experiments revealed no relation between the opioid effects on membrane electrical events and twitch potentiation. Blocking slow calcium channels with D-600 did not modify the opioid-induced twitch potentiation. The twitch potentiation was antagonized by increasing the extracellular calcium concentration, [Ca2+]o, to 8.64 mM. The effects of closely spaced multiple electrical pulses revealed that the opioids decreased the summated response relative to predrug controls. The results suggest that opioids facilitate the process of excitation-contraction coupling in the frog's skeletal muscle by the release of an additional amount of "trigger calcium" following a single electrical stimulus, thereby generating a potentiated twitch.
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Shetty SS, Frank GB. Displacement of the surface membrane bound calcium of the skeletal muscle fibers of the frog: effects of lanthanum and opioids. J Pharmacol Exp Ther 1985; 234:233-8. [PMID: 3874282] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Three opioids, viz. methadone, morphine and meperidine, were tested separately for their effects on the rate of 45Ca++ efflux from frog toe muscles. The experimental procedures were designed to provide reliable measurements of the displacement of 45Ca++ from surface binding sites using the thin and light toe muscle. La (2 mM) was used to test the ability of the experimental procedure to detect the displacement of calcium bound superficially to the muscle fiber membrane. La not only enhances the rate of efflux of 45Ca++ from surface membrane superficial stores but also inhibits the efflux of intracellular calcium. Of the opioids tested, only methadone (10(-4) or 10(-3) M) caused a slight but significant increase in the rate of 45Ca++ efflux from the surface bound (i.e., the La -displaceable) store of calcium of the muscle. The "calcium-displacement" effect of methadone was much weaker than that seen with La . Morphine (10(-4) or 10(-3) M) or meperidine (10(-4) or 10(-3) M) did not show any such effect on the bound 45Ca++ desaturation rate even under experimental conditions modified to enable the detection of the displacement of even small amounts of 45Ca++ from superficial binding sites on the muscles.
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Abstract
Morphine and several other opioid agonists including the enkephalins caused a dual action on the twitch in the isolated, curarized, and electrically stimulated frog toe muscle; a potentiating action at low drug concentrations and a potentiation followed by an inhibitory action at higher concentrations. The twitch potentiation was found to be nonstereospecific and resistant to antagonism by naloxone. The inhibitory action too was naloxone-resistant and is probably due to a nonspecific local anesthetic effect of the opioids on the electric properties of the frog skeletal muscle fibre membrane.
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