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Feng X, Zan G, Wei Y, Ge X, Cai H, Long T, Xie L, Tong L, Liu C, Li L, Huang L, Wang F, Chen X, Zhang H, Zou Y, Zhang Z, Yang X. Relationship of multiple metals mixture and osteoporosis in older Chinese women: An aging and longevity study. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2023; 317:120699. [PMID: 36403877 DOI: 10.1016/j.envpol.2022.120699] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/14/2022] [Revised: 10/21/2022] [Accepted: 11/17/2022] [Indexed: 06/16/2023]
Abstract
Osteoporosis has become a major health problem in older women. Previous studies have linked individual metals exposure with osteoporosis, but combined effects remain inconclusive. We aimed to explore the individual and combined association between multiple metals mixture and osteoporosis risk in older Chinese women. A total of 2297 older women (aged ≥60) from the Hongshuihe region of Guangxi, southern China included. We measured 22 blood metal levels through inductively coupled plasma mass spectrometry. And osteoporosis was defined as a T score ≤ -2.5. The least absolute shrinkage and selection operator (LASSO) penalized regression, and Bayesian kernel machine regression (BKMR) models were performed to explore the association between blood metals and osteoporosis risk. Of 2297 older women, there were 829 osteoporosis and 1468 non-osteoporosis participants. The median age was 71 and 68 years old in the osteoporosis and the non-osteoporosis group, respectively. In the single-metal model, rubidium and vanadium were negatively associated with osteoporosis (P for trend = 0.02 and 0.002, respectively), and lead presented the reverse trend (P for trend = 0.01). The LASSO penalized regression model selected nine metals (calcium, cadmium, cobalt, lead, magnesium, rubidium, strontium, vanadium and zinc), which were included in the subsequent analysis. And the multiple-metal model presented a consistent trend with the single-metal model using the selected metals. Furthermore, we performed BKMR to explore the combined effect, and found an overall negative effect between metals mixture and osteoporosis risk when all the metals were fixed at 50th, and rubidium and vanadium were the main contributors. In addition, blood Rb and V were significantly negatively related to OP risk with other metals at different levels (25th, 50th and 75th percentiles). The study suggests metal mixture exposure and osteoporosis risk in older Chinese women, and further studies need to be conducted.
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Affiliation(s)
- Xiuming Feng
- Department of Occupational Health and Environmental Health, School of Public Health, Guangxi Medical University, Nanning, Guangxi, China; Center for Genomic and Personalized Medicine, Guangxi Key Laboratory for Genomic and Personalized Medicine, Guangxi Collaborative Innovation Center for Genomic and Personalized Medicine, Guangxi Medical University, Nanning, Guangxi, China
| | - Gaohui Zan
- Department of Occupational Health and Environmental Health, School of Public Health, Guangxi Medical University, Nanning, Guangxi, China; Center for Genomic and Personalized Medicine, Guangxi Key Laboratory for Genomic and Personalized Medicine, Guangxi Collaborative Innovation Center for Genomic and Personalized Medicine, Guangxi Medical University, Nanning, Guangxi, China
| | - Yue Wei
- Department of Occupational Health and Environmental Health, School of Public Health, Guangxi Medical University, Nanning, Guangxi, China
| | - Xiaoting Ge
- Department of Public Health, School of Medicine, Guangxi University of Science and Technology, Liuzhou, Guangxi, China
| | - Haiqing Cai
- Department of Occupational Health and Environmental Health, School of Public Health, Guangxi Medical University, Nanning, Guangxi, China
| | - Tianzhu Long
- Department of Occupational Health and Environmental Health, School of Public Health, Guangxi Medical University, Nanning, Guangxi, China
| | - Lianguang Xie
- Department of Occupational Health and Environmental Health, School of Public Health, Guangxi Medical University, Nanning, Guangxi, China; Department of Public Health, School of Medicine, Guangxi University of Science and Technology, Liuzhou, Guangxi, China
| | - Lei Tong
- Department of Occupational Health and Environmental Health, School of Public Health, Guangxi Medical University, Nanning, Guangxi, China
| | - Chaoqun Liu
- Department of Nutrition and Food Hygiene, School of Public Health, Guangxi Medical University, Nanning, Guangxi, China
| | - Longman Li
- Center for Genomic and Personalized Medicine, Guangxi Key Laboratory for Genomic and Personalized Medicine, Guangxi Collaborative Innovation Center for Genomic and Personalized Medicine, Guangxi Medical University, Nanning, Guangxi, China
| | - Lulu Huang
- Center for Genomic and Personalized Medicine, Guangxi Key Laboratory for Genomic and Personalized Medicine, Guangxi Collaborative Innovation Center for Genomic and Personalized Medicine, Guangxi Medical University, Nanning, Guangxi, China
| | - Fei Wang
- Department of Occupational Health and Environmental Health, School of Public Health, Guangxi Medical University, Nanning, Guangxi, China
| | - Xing Chen
- Department of Sanitary Chemistry, School of Public Health, Guangxi Medical University, Nanning, Guangxi, China
| | - Haiying Zhang
- Department of Occupational Health and Environmental Health, School of Public Health, Guangxi Medical University, Nanning, Guangxi, China
| | - Yunfeng Zou
- Department of Toxicology, School of Public Health, Guangxi Medical University, Nanning, 530021, China
| | - Zhiyong Zhang
- School of Public Health, Guilin Medical University, Guilin, Guangxi, China
| | - Xiaobo Yang
- Department of Occupational Health and Environmental Health, School of Public Health, Guangxi Medical University, Nanning, Guangxi, China; Center for Genomic and Personalized Medicine, Guangxi Key Laboratory for Genomic and Personalized Medicine, Guangxi Collaborative Innovation Center for Genomic and Personalized Medicine, Guangxi Medical University, Nanning, Guangxi, China.
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Liu Y, Yuan Y, Xiao Y, Li Y, Yu Y, Mo T, Jiang H, Li X, Yang H, Xu C, He M, Guo H, Pan A, Wu T. Associations of plasma metal concentrations with the decline in kidney function: A longitudinal study of Chinese adults. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2020; 189:110006. [PMID: 31812020 DOI: 10.1016/j.ecoenv.2019.110006] [Citation(s) in RCA: 52] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/13/2019] [Revised: 11/16/2019] [Accepted: 11/23/2019] [Indexed: 06/10/2023]
Abstract
Metals are widespread pollutants in the environment which have been reported to be associated with kidney dysfunction in many existing epidemiological studies. However, most of the studies are cross-sectional design and mainly focus on several toxic metals including arsenic, lead and cadmium. Therefore, we conducted this prospective study within the Dongfeng-Tongji cohort to evaluate the associations of plasma multiple metals with the decline in kidney function among Chinese middle-aged and elderly. In total, 1434 participants free of chronic diseases at baseline were included in analysis. We measured baseline plasma concentrations of 23 metals and calculated estimated glomerular filtration rate (eGFR) using the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation based on serum creatinine, age, sex and ethnicity. Bonferroni correction was used for multiple testing to reduce the probability of a type I error. Principal component analysis was conducted to evaluate the combined effect of multiple metal co-exposure. Most of the plasma metal concentrations were within the literature reported reference values, whereas the concentration of lead and nickel exceeded the guideline value. We found that plasma concentrations of aluminum, arsenic, barium, lead, molybdenum, rubidium, strontium, vanadium and zinc were significantly associated with the decline in kidney function measured by annual eGFR decline, rapid renal function decline (defined as an annual decline in eGFR ≥ 5 mL/min/1.73 m2) or incident eGFR < 60 mL/min/1.73 m2, with the adjusted beta coefficients (95% CI) for annual eGFR decline 0.50 (0.30, 0.69), 0.98 (0.74, 1.23), 0.56 (0.32, 0.79), 0.21 (0.03, 0.39), 0.35 (0.16, 0.54), 0.94 (0.71, 1.17), 0.37 (0.15, 0.60), 0.78 (0.54, 1.02), and 0.74 (0.57, 0.91), respectively. The metals exposures were linked with increased risks of impaired kidney function. Associations of principal components representing these metals with the decline in kidney function were significant and suggest a possible additional health risk by co-exposure. Participants engaged in manufacturing had higher plasma levels of several metals compared with those who had been involved in management- or administration-related work. Our findings suggest that exposure to multiple metals contribute to the decline in kidney function among the middle-aged and elderly. Co-exposure to multiple metals may have synergetic effect on the kidney function. Further studies are warranted to confirm our findings and clarify the potential mechanisms.
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Affiliation(s)
- Yiyi Liu
- Department of Occupational and Environmental Health Key Laboratory of Environment and Health, Ministry of Education and State Key Laboratory of Environmental Health (Incubating), School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, PR China
| | - Yu Yuan
- Department of Occupational and Environmental Health Key Laboratory of Environment and Health, Ministry of Education and State Key Laboratory of Environmental Health (Incubating), School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, PR China.
| | - Yang Xiao
- Department of Occupational and Environmental Health Key Laboratory of Environment and Health, Ministry of Education and State Key Laboratory of Environmental Health (Incubating), School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, PR China
| | - Yizhun Li
- Department of Occupational and Environmental Health Key Laboratory of Environment and Health, Ministry of Education and State Key Laboratory of Environmental Health (Incubating), School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, PR China
| | - Yanqiu Yu
- Department of Occupational and Environmental Health Key Laboratory of Environment and Health, Ministry of Education and State Key Laboratory of Environmental Health (Incubating), School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, PR China
| | - Tingting Mo
- Department of Occupational and Environmental Health Key Laboratory of Environment and Health, Ministry of Education and State Key Laboratory of Environmental Health (Incubating), School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, PR China
| | - Haijing Jiang
- Department of Occupational and Environmental Health Key Laboratory of Environment and Health, Ministry of Education and State Key Laboratory of Environmental Health (Incubating), School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, PR China
| | - Xiulou Li
- Department of Cardiovascular Diseases, Dongfeng Central Hospital, Hubei University of Medicine, Shiyan, 442000, PR China
| | - Handong Yang
- Department of Cardiovascular Diseases, Dongfeng Central Hospital, Hubei University of Medicine, Shiyan, 442000, PR China
| | - Chengwei Xu
- Department of Cardiovascular Diseases, Dongfeng Central Hospital, Hubei University of Medicine, Shiyan, 442000, PR China
| | - Meian He
- Department of Occupational and Environmental Health Key Laboratory of Environment and Health, Ministry of Education and State Key Laboratory of Environmental Health (Incubating), School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, PR China
| | - Huan Guo
- Department of Occupational and Environmental Health Key Laboratory of Environment and Health, Ministry of Education and State Key Laboratory of Environmental Health (Incubating), School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, PR China
| | - An Pan
- Department of Epidemiology and Biostatistics, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, PR China
| | - Tangchun Wu
- Department of Occupational and Environmental Health Key Laboratory of Environment and Health, Ministry of Education and State Key Laboratory of Environmental Health (Incubating), School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, PR China
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Higashi H, Kinjo T, Uno K, Kuramoto N. Regulatory effects associated with changes in intracellular potassium level in susceptibility to mitochondrial depolarization and excitotoxicity. Neurochem Int 2019; 133:104627. [PMID: 31805298 DOI: 10.1016/j.neuint.2019.104627] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2019] [Revised: 11/16/2019] [Accepted: 12/02/2019] [Indexed: 12/12/2022]
Abstract
Excitotoxicity has been believed to be one of the causes of neurodegenerative diseases such as Alzheimer's disease and Huntington's disease. So far, much research has been done to suppress the neuronal excessive excitations, however, we still have not achieved full control, which may be due to the lack of some factors. As a matter of course, there is an urgent need to clarify all mechanisms that inhibit the onset and progression of neurodegenerative diseases. We found that potassium ion level regulation may be important in the sense that it suppresses mitochondrial depolarization rather than hyperpolarization of cell membrane potential. Minoxidil, an opener of ATP-activated potassium (KATP) channels decreased injury with middle cerebral artery occlusion in vivo experiment using TTC staining. In the primary cortical neurons, N-methyl-D-aspartate (NMDA)-induced mitochondrial depolarization was suppressed by minoxidil treatment. Minoxidil inhibited the increase in levels of cleaved caspase 3 and the release of cytochrome c into the cytosol, further reducing potassium ion levels. It was observed decreased potassium levels in neurons by the treatment of minoxidil. Those effects of minoxidil were blocked by glibenclamide. Therefore, it was suggested that minoxidil, via opening of KATP channels, reduced intracellular potassium ion level that contribute to mitochondrial depolarization, and suppressed subsequent NMDA-induced mitochondrial depolarization. Our findings suggest that the control of ion levels in neurons could dominate the onset and progression of neurodegenerative diseases.
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Affiliation(s)
- Hiroshi Higashi
- Laboratory of Molecular Pharmacology, Faculty of Pharmaceutical Sciences, Setsunan University, Hirakata, Osaka, 573-0101, Japan
| | - Toshihiko Kinjo
- Laboratory of Molecular Pharmacology, Faculty of Pharmaceutical Sciences, Setsunan University, Hirakata, Osaka, 573-0101, Japan
| | - Kyosuke Uno
- Laboratory of Molecular Pharmacology, Faculty of Pharmaceutical Sciences, Setsunan University, Hirakata, Osaka, 573-0101, Japan
| | - Nobuyuki Kuramoto
- Laboratory of Molecular Pharmacology, Faculty of Pharmaceutical Sciences, Setsunan University, Hirakata, Osaka, 573-0101, Japan.
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Usuda K, Kono R, Ueno T, Ito Y, Dote T, Yokoyama H, Kono K, Tamaki J. Risk assessment visualization of rubidium compounds: comparison of renal and hepatic toxicities, in vivo. Biol Trace Elem Res 2014; 159:263-8. [PMID: 24728875 DOI: 10.1007/s12011-014-9937-3] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/22/2014] [Accepted: 03/05/2014] [Indexed: 11/26/2022]
Abstract
Rubidium has been considered to be nontoxic. Its use includes thin film on glass deposition and as medical contrast medium. Recent technology innovations also involve the use of rubidium, but there is limited information about the biological effects of its various compounds. In the present risk assessment study, a series of rubidium compounds with different counter anions-acetate, bromide, carbonate, chloride, and fluoride-were orally administrated in a single dose to several groups of rats. Cumulative 24-h urine samples were obtained, and the levels of rubidium, fluoride, N-acetyl-β-D-glucosaminidase and creatinine were measured to evaluate possible acute renal effects. Daily samples of serum were also obtained to determine the levels of aspartate and alanine aminotransferases to assess possible acute hepatic effects. Urinary rubidium excretion recovery of 8.0-10.5% shows that urine can be a useful diagnostic tool for rubidium exposure. The present results reveal that rubidium shows different biological effects depending on the counter anion. A pattern of large significant NAG leakage and elevation of ALT observed in rats treated with anhydrous rubidium fluoride indicates renal and hepatic toxicities that can be attributed to fluoride. The techniques reported in this study will be of help to assess the potential risks of toxicity of rubidium compounds with a variety of anions.
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Affiliation(s)
- Kan Usuda
- Department of Hygiene and Public Health, Division of Preventive and Social Medicine, Faculty of Medicine, Osaka Medical College, 2-7, Daigakumachi, Takatsuki City, Osaka, 569-8686, Japan,
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Novaković A, Gojković-Bukarica L, Beleslin-Cokić B, Japundzić-Zigon N, Sajić Z, Nezić D, Perić M, Djukanović B, Kazić T. Differential antivasoconstrictor effects of levcromakalim and rilmakalim on the isolated human mammary artery and saphenous vein. J Pharmacol Sci 2003; 92:108-14. [PMID: 12832838 DOI: 10.1254/jphs.92.108] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
Abstract
It is well established that spasm of an arterial and venous graft conduit may occur during harvesting or after coronary artery bypass grafting (CABG). The antivasoconstrictor effect of levcromakalim and rilmakalim, K(+) channel openers (KCOs), was studied in isolated human internal mammary artery (HIMA) and human saphenous vein (HSV) prepared for CABG. HIMA and HSV rings were contracted by electrical field stimulation (EFS, 20 Hz ) or with exogenous noradrenaline (NA). Levcromakalim induced a concentration-dependent and equipotent inhibition of contraction of HIMA and HSV preconstricted by EFS and exogenoulsy applied NA, while rilmakalim produced a stronger inhibition of EFS- than NA-evoked contractions. Glibenclamide, a selective ATP-sensitive K(+) channel (K(ATP) channel) blocker, significantly antagonized levcromakalim-induced inhibition of EFS- and NA-evoked contractions, as well as rilmakalim-induced inhibiton of EFS-evoked contractions on HIMA and HSV. However, glibenclamide failed to antagonize rilmakalim-induced inhibition of NA-evoked contractions. The results suggest that the antivasoconstrictor effect of levcromakalim occurs postsynapticaly by the opening K(ATP) channels in the vascular smooth muscle cells. They also suggest that the effect of rilmakalim on EFS-evoked contractions involves K(ATP) channels located pre-synaptically. However, the mechanism by which rilmakalim inhibits NA-evoked contraction seems to be K(ATP) channel independent and warrants further elucidation.
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Affiliation(s)
- Aleksandra Novaković
- Department of Pharmacology, Faculty of Pharmacy, University of Belgrade, Belgrade, Serbia and Montenegro
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Criddle DN, de Moura RS. Vasorelaxant effects of the potassium channel opener SR 47063 on the isolated human saphenous vein and rat aorta. Braz J Med Biol Res 2000; 33:961-6. [PMID: 10920439 DOI: 10.1590/s0100-879x2000000800013] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The vasorelaxant effects of SR 47063 (4-(2-cyanimino-1, 2-dihydropyrid-1-yl)-2,2-dimethyl-6-nitr ochromene), a new K(+)-channel opener structurally related to levcromakalim, were examined in isolated human saphenous vein (HSV) and rat aorta (RA). HSV or RA rings were precontracted with either KCl or noradrenaline and cumulative relaxant concentration-response curves were obtained for SR 47063 (0.1 nM to 1 microM) in the presence or absence of 3 microM glibenclamide. SR 47063 potently relaxed HSV and RA precontracted with 20 mM (but not 60 mM) KCl or 10 microM noradrenaline in a concentration-dependent manner, showing slightly greater activity in the aorta. The potency of the effect of SR 47063 on HSV and RA was 12- and 58-fold greater, respectively, than that reported for the structurally related K(+)-channel opener levcromakalim. The vasorelaxant action of SR 47063 in both blood vessels was strongly inhibited by 3 microM glibenclamide, consistent with a mechanism of action involving ATP-dependent K(+)-channels.
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Affiliation(s)
- D N Criddle
- Departamento de Ciências Fisiológicas, Centro de Ciências da Saúde, Universidade Estadual do Ceará, Fortaleza, CE, Brasil.
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Gojković-Bukarica L, Kazić T. Differential effects of pinacidil and levcromakalim on the contractions elicited electrically or by noradrenaline in the portal vein of the rabbit. Fundam Clin Pharmacol 1999; 13:527-34. [PMID: 10520724 DOI: 10.1111/j.1472-8206.1999.tb00357.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
The present study was undertaken to examine the antivasoconstrictor effects of pinacidil and levcromakalim, two potassium channel openers (PCOs), on the isolated rabbit portal vein and to define the role for different subtypes of pre- and/or post-synaptic K+ channels in the antivasoconstrictor action of the PCOs. The vein strips were contracted by electrical field stimulation (EFS) or by exogenous noradrenaline (NA). The results of this study showed that pinacidil produced a more potent inhibition of the neurogenic contractions (pD2 = 6.04 +/- 0.05) than of contractions induced by exogenous NA (pD2 = 4.90 +/- 0.10). Glibenclamide (1 microM), a selective blocker of adenosine triphosphate (ATP)-sensitive K+ channels (K(ATP)), did not affect the pinacidil-induced inhibition of contractions evoked by exogenous NA. In contrast, glibenclamide (0.1-10 microM) significantly antagonized the effect of pinacidil on EFS evoked contractions in a noncompetitive manner. There was no difference between the inhibitory effects of levcromakalim on neurogenic contractions (pD2 = 7.58 +/- 0.05) and contractions evoked by exogenous NA (pD2 = 7.64 +/- 0.08). Glibenclamide (1 microM) antagonized in the same manner the levcromakalim-induced inhibition of neurogenic contractions and contractions evoked by exogenous NA. Moreover, glibenclamide competitively antagonized the effect of levcromakalim on EFS induced contractions of the rabbit portal vein (pA2 = 6.40 +/- 0.10). Charybdotoxin (0.4 microM) and apamin (0.1 microM) did not influence the inhibitory effects of pinacidil and levcromakalim, both on contractions evoked by EFS and contractions evoked by exogenous NA. These results suggest that the antivasoconstrictor effect of levcromakalim might be postsynaptic and associated with opening of the smooth muscle K(ATP) channels. In contrast, it is hypothesized that the effect of pinacidil on neurogenic contractions is due to an interference with K(ATP) channels in the neuromuscular synapse. It seems that the action of pinacidil on the NA contractions is mediated by another still undefined mechanisms of pinacidil.
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Affiliation(s)
- L Gojković-Bukarica
- Department of Clinical Pharmacology, Pharmacology and Toxicology, Medical Faculty, Belgrade, Yugoslavia
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Kwan YW, To KW, Lau WM, Tsang SH. Comparison of the vascular relaxant effects of ATP-dependent K+ channel openers on aorta and pulmonary artery isolated from spontaneously hypertensive and Wistar-Kyoto rats. Eur J Pharmacol 1999; 365:241-51. [PMID: 9988108 DOI: 10.1016/s0014-2999(98)00768-7] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The vasorelaxant actions of adenosine 5'-triphosphate (ATP)-dependent K+ channel openers and sodium nitroprusside in isolated thoracic aorta and pulmonary artery of spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto (WKY) rats (14-18 weeks old) were investigated. Cumulative addition of sodium nitroprusside and different ATP-dependent K+ channel openers (pinacidil, cromakalim, nicorandil, 2-(2"(1",3"-dioxolone)-2-methyl-4-(2'-oxo-1'-pyrrolidinyl)-6-nitro -2H-1-benzopyren (KR-30450) and aprikalim) to these preparations caused a concentration-dependent relaxation of noradrenaline-pre-contracted aorta and pulmonary artery from both strains. The relative order of relaxation potency, estimated by comparing the IC50, was sodium nitroprusside > KR-30450 > aprikalim > or = cromakalim > pinacidil > nicorandil in pulmonary artery and aorta from both strains. At high concentrations (> or =1 microM), cromakalim, aprikalim and KR-30450 produced a greater percentage relaxation in SHR aorta than in WKY aorta. However, there was no apparent difference between SHR and WKY in the relaxation response to all drugs tested on the pulmonary artery. The effects of cromakalim, aprikalim, pinacidil and KR-30450 observed in aorta and pulmonary artery were significantly attenuated by 3 microM glibenclamide. 6-Anilino-5,8-quinolinequinone (LY 83583, 1 microM), a soluble guanylate cyclase inhibitor, abolished the vasorelaxant effects of nicorandil and sodium nitroprusside. In conclusion, sodium nitroprusside and ATP-dependent K+ channel openers cause relaxation of noradrenaline-pre-contracted aorta and pulmonary artery from both strains. However, all the drugs tested failed to cause selective relaxation of the pulmonary artery relative to the thoracic aorta.
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Affiliation(s)
- Y W Kwan
- Department of Pharmacology, Faculty of Medicine, The Chinese University of Hong Kong, China.
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Deka DK, Raviprakash V, Mishra SK. Basal nitric oxide release differentially modulates vasodilations by pinacidil and levcromakalim in goat coronary artery. Eur J Pharmacol 1998; 348:11-23. [PMID: 9650826 DOI: 10.1016/s0014-2999(98)00066-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
In the current investigation, the role of basal nitric oxide (NO) in modulating the vasorelaxant responses to pinacidil and levcromakalim was examined in goat isolated coronary artery. Pinacidil (10(-8) 10(-4) M) elicited concentration-dependent relaxations of the coronary artery ring segments (with intact endothelium) constricted with 30 mM K+ saline solution. The EC50 of the vasodilator was 2.57 x 10(-6) M (95% CL, 1.9-3.46 x 10(-6) M). The removal of endothelium by mechanical rubbing caused a rightward shift in the concentration-response curve of pinacidil with a corresponding increase in EC50 value (1.90 x 10(-5) M; 95% CL, 1.12-3.23 x 10(-5) M). Similar to endothelium removal, treatment of endothelium-intact rings either with the NO synthesis inhibitor L-NAME (NG-nitro-L-arginine methyl ester; 3 x 10(-5) M) or the guanylate cyclase inhibitor, methylene blue (3 x 10(-6) M) resulted in a marked inhibition in the relaxant responses to pinacidil. Hence, the EC50 values of the potassium channel opener were significantly higher in tissues treated either with L-NAME (7.41 x 10(-6) M; 95% CL, 6.02-9.12 x 10(-6) M) or methylene blue (2.29 x 10(-5) M; 95% CL, 1.58-3.31 x 109-5) M) as compared to untreated controls. The ATP-sensitive potassium (KATP) channel blocker glibenclamide, which caused a significant rightward shift in the concentration-relaxation curve of pinacidil in control tissues, was found to be less potent in antagonising the relaxant responses of the KATP channel opener in endothelium-denuded rings and in rings with intact endothelium but treated with either L-NAME or methylene blue. In contrast to the observations made with pinacidil, the vasodilator responses to another KATP channel opener, levcromakalim, were potentiated in the absence of basal NO. Thus, the EC50 of levcromakalim was 1.33 x 10(-8) M (95% CL, 0.8-2.21 x 10(-8) M) in control tissues with intact endothelium, which was significantly higher than those obtained in endothelium-deprived rings (4.81 x 10(-9) M; 95% CL, 4.04-5.73 x 10(-9) M) or endothelium intact rings treated either with L-NAME (2.63 x 10(-9) M; 95% CL, 1.58-4.36 x 10(-9) M) or methylene blue (2.82 x 10(-9) M; 95% CL, 1.7-4.68 x 10(-9) M). The selective modulation by basal NO of the arterial relaxations elicited with the KATP channel openers was evident from the findings that papaverine-induced relaxations were not affected in the absence of basal NO. Taken together, the results of the present study suggest that basal NO differentially modulates the interaction of pinacidil and levcromakalim with the KATP channels in goat coronary artery through a cGMP-dependent pathway.
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Affiliation(s)
- D K Deka
- Division of Pharmacology and Toxicology, Indian Veterinary Research Institute, Izatnagar, UP
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Teramoto N, Brading AF. The effects of nifedipine and other calcium antagonists on the glibenclamide-sensitive K+ currents in smooth muscle cells from pig urethra. Br J Pharmacol 1998; 123:1601-8. [PMID: 9605567 PMCID: PMC1565332 DOI: 10.1038/sj.bjp.0701777] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
1. The effects of nifedipine on both levcromakalim-induced membrane currents and unitary currents in pig proximal urethra were investigated by use of patch-clamp techniques (conventional whole-cell configuration and cell-attached patches). 2. Nifedipine had a voltage-dependent inhibitory effect on voltage-dependent Ba2+ currents at - 50 mV (Ki=30.6 nM). 3. In current-clamp mode, subsequent application of higher concentrations of nifedipine (> or =30 microM) caused a significant depolarization even after the membrane potential had been hyperpolarized to approximately -82 mV by application of 100 microM levcromakalim. 4. The 100 microM levcromakalim-induced inward current (symmetrical 140 mM K+ conditions, -50 mV) was inhibited by additional application of three different types of Ca antagonists (nifedipine, verapamil and diltiazem, all at 100 microM). In contrast, Bay K 8644 (1 microM) possessed no activating effect on the amplitude of this glibenclamide-sensitive current. 5. When 100 microM nifedipine was included in the pipette solution during conventional whole-cell recording at -50 mV, application of levcromakalim (100 microM) caused a significant inward membrane current which was suppressed by 5 microM glibenclamide. On the other hand, inclusion of 5 microM glibenclamide in the pipette solution prevented levcromakalim from inducing an inward membrane current. 6. The levcromakalim-induced K+ channel openings in cell-attached configuration were suppressed by subsequent application of 5 microM glibenclamide but not of 100 microM nifedipine. 7. These results suggest that in pig proximal urethra, nifedipine inhibits the glibenclamide-sensitive 43 pS K+ channel activity mainly through extracellular blocking actions on the K+ channel itself.
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Affiliation(s)
- N Teramoto
- University Department of Pharmacology, Oxford
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12
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Gojkoviíc Bukarica L, Kazić T, Sajić Z, Djukanović B, Panić G, Perić M, Bojić M. The effects of levcromakalim and pinacidil on the human internal mammary artery. Fundam Clin Pharmacol 1998; 11:550-60. [PMID: 9444523 DOI: 10.1111/j.1472-8206.1997.tb00860.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The present study was undertaken to examine the effects of pinacidil and levcromakalim, two potassium, channel openers, on human internal mammary artery (HIMA) obtained from patients undergoing coronary artery bypass surgery, and to clarify the contribution of different K+ channel subtypes in pinacidil and levcromakalim action in this blood vessel. Pinacidil and levcromakalim induced a concentration-dependent relaxation of the precontracted arterial segments (pEC50 = 5.77 +/- 0.05 and 6.89 +/- 0.03, respectively), 4-Aminopyridine (3 mM), a non-selective blocker of K+ channels, induced significant shifts to the right of the concentration-response curves for pinacidil and levcromakalim. Tetraethylammonium (6 mM), charybdotoxin (0.4 microM) and apamin (0.1 microM), blockers of Ca(2+)-sensitive K+ channels, had no effect on the pinacidil- and levcromakalim-evoked relaxation. Glibenclamide (0.1-10 microM), a selective blocker of adenosine triphosphate (ATP)-sensitive K+ channels, competitively antagonized the response to levcromakalim (pKB = 7.92 +/- 0.07). In contrast, glibenclamide, in significantly higher concentrations (3-30 microM), non-competitively antagonized the response to pinacidil. High concentrations of pinacidil (> 10 microM) relaxed arterial rings bathed by a medium containing 100 mM K+ with maximum response 83 +/- 6%. Under the same conditions, the maximum levcromakalim-induced relaxation on HIMA was almost abolished (15 +/- 2%). It is concluded that pinacidil and levcromakalim do not relax the HIMA through the same subtype of K+ channel. ATP-sensitive K+ channels are probably involved in levcromakalim- but not in a pinacidil-induced relaxation in the HIMA. In addition, in pinacidil-induced relaxation of the HIMA, K+ channel-independent mechanisms seem to be involved.
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13
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Criddle DN, de Moura RS, Greenwood IA, Large WA. Effect of niflumic acid on noradrenaline-induced contractions of the rat aorta. Br J Pharmacol 1996; 118:1065-71. [PMID: 8799583 PMCID: PMC1909505 DOI: 10.1111/j.1476-5381.1996.tb15507.x] [Citation(s) in RCA: 76] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
1. The effects of niflumic acid, an inhibitor of calcium-activated chloride channels, were compared with the actions of the calcium channel antagonist nifedipine on noradrenaline-evoked contractions in isolated preparations of the rat aorta. 2. The cumulative concentration-effect curve to noradrenaline (NA) was depressed by both nifedipine and niflumic acid in a reversible and concentration-dependent manner. The degree of inhibition of the maximal contractile response to NA (1 microM) produced by 10 microM niflumic acid (38%) was similar to the effect of 1 microM nifedipine (39%). 3. Contractions to brief applications (30 s) of 1 microM NA were inhibited by 55% and 62% respectively by 10 microM niflumic acid and 1 microM nifedipine. 4. In the presence of 0.1 microM nifedipine, niflumic acid (10 microM) produced no further inhibition of the NA-evoked contractions. Thus, the actions of niflumic acid and nifedipine were not additive. 5. In Ca-free conditions the transient contraction induced by 1 microM NA was not inhibited by niflumic acid (10 microM) and therefore this agent does not reduce the amount of calcium released from the intracellular store or reduce the sensitivity of the contractile apparatus to calcium. 6. Niflumic acid 10 microM did not inhibit the contractions produced by KCl (up to 120 mM) which were totally blocked by nifedipine. Contractions induced by 25 mM KCl were completely inhibited by 1 microM levcromakalim but were unaffected by niflumic acid. 7. It was concluded that niflumic acid produces selective inhibition of a component of NA-evoked contraction which is probably mediated by voltage-gated calcium channels. These data are consistent with a model in which NA stimulates a calcium-activated chloride conductance which leads to the opening of voltage-gated calcium channels to produce contraction.
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Affiliation(s)
- D N Criddle
- Departmento de Farmacologia, Centro Biomédico-IB, Universidade do Estado do Rio de Janeiro, Brasil
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14
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Abstract
The physiological role of K+ channel opening by endogenous substances (e.g., neurotransmitters and hormones) is a recognised inhibitory mechanism. Thus, the identification of novel synthetic molecules that 'directly' open K+ channels has led to a new direction in the pharmacology of ion channels. The existence of many different subtypes of K+ channels has been an impetus in the search for new molecules demonstrating channel and, thus, tissue selectivity. This review focuses on the different classes of openers of K+ channels, the intracellular mechanisms involved in the execution of their effects, and potential therapeutic targets.
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Affiliation(s)
- K Lawson
- Division of Biomedical Sciences, School of Science, Sheffield Hallam University, UK
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Quast U, Baumlin Y, Loffler C. Ba2+ differentially inhibits the Rb+ efflux promoting and the vasorelaxant effects of levcromakalim and minoxidil sulfate in rat isolated aorta. NAUNYN-SCHMIEDEBERG'S ARCHIVES OF PHARMACOLOGY 1995; 353:86-93. [PMID: 8750921 DOI: 10.1007/bf00168920] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The K+ channel openers activate ATP-sensitive K+ channels (KATP) in vascular smooth muscle and induce relaxation. In this study, the relationship between these two effects was examined in rings of rat aorta using levcromakalim and minoxidil sulfate as the openers and Ba2+ as the K+ channel blocker; K+ channel opening was assessed by determining the rate constant of 86Rb+ efflux from the preparation. Ba2+ inhibited the 86Rb+ efflux stimulated by levcromakalim in a noncompetitive manner with an IC50 value of 29 microM and a Hill-coefficient of 1.2. At concentrations >300 microM, Ba2+ increased the tension of rat aortic rings concentration-dependently. Levcromakalim relaxed contractions to Ba2+ (0.5 and 1 mM) with potencies similar to those determined against KCl (25 mM) or noradrenaline as spasmogens (EC50 values 15-40 nM). The vasorelaxant effect against Ba2+ was inhibited by the KATP channel blockers, glibenclamide and tedisamil, and abolished in depolarizing medium (55 mM KCl). At 3 mM Ba2+, levcromakalim was still able to transiently induce complete relaxation; however, within 1 h oscillations in tension developed, leading to a stable level of only 15% relaxation. A similar level of relaxation was achieved against 10 mM Ba2+ whereas the combination of 0.5 mM Ba2+ and 3 microM tedisamil blocked the relaxant effect of levcromakalim completely. With minoxidil sulfate as the KATP channel opener the results of the 86Rb+ efflux and tension experiments were similar to those obtained with levcromakalim. It is concluded that Ba2+ is more potent in inhibiting the K+ channel opening than the vasorelaxant effects of the openers. On the basis of the 86Rb+ efflux experiments it is estimated that at least 97% of the channels opened by the activators can be blocked without major effects on vasorelaxation suggesting a dissociation between the two effects. However, if the block is pushed to extremes (> or = 99.95%) the vasorelaxant effect of the openers is also abolished suggesting a link between both effects. This paradoxon remains to be solved.
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Affiliation(s)
- U Quast
- Department of Pharmacology, University of Tubingen, Germany
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16
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Hughes SJ, Hollingsworth M. Cellular localization of the inhibitory action of relaxin against uterine spasm. Br J Pharmacol 1995; 116:3028-34. [PMID: 8680739 PMCID: PMC1909230 DOI: 10.1111/j.1476-5381.1995.tb15959.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
1. The aim of this study was to determine whether the site of action of relaxin as a relaxant of rat myometrium is at the cell membrane or at an intracellular-site. Therefore, the potency of relaxin was determined against spasms reliant predominantly upon either extracellular Ca2+ or intracellular Ca2+. Uterine spasms dependent upon extracellular Ca2+ were elicited by (i) oxytocin (0.2 nM) (ii) Bay K 8644 (1 microM) in 10 mM K(+)-rich PSS and (iii) KCl (80 mM). Uterine spasm dependent upon intracellular Ca2+ was elicited by oxytocin (20 nM) in the presence of nifedipine (500 nM). The effects of relaxin against these spasmogens were compared with those of levcromakalim, nifedipine and salbutamol. 2. Relaxin (0.2-6.3 nM), levcromakalim (25-800 nM), salbutamol (1-63 nM) and nifedipine (1-250 nM) caused concentration-dependent inhibition of the spasm evoked by oxytocin (0.2 nM) and relaxin was the most potent relaxant. 3. Relaxin and nifedipine were slightly less potent against the spasm induced by Bay K 8644 (1 microM) than against spasm induced by oxytocin (0.2 nM) (15 fold and 13 fold respectively). Levcromakalim and salbutamol were equipotent against the spasm evoked by Bay K 8644 (1 microM) and that evoked by oxytocin (0.2 nM). 4. Relaxin induced only 47 +/- 7% inhibition of the KCl (80 mM)-evoked spasm at a concentration of 0.8 microM. Levcromakalim was much less potent (427 fold) against the spasm evoked by KCl (80 mM) than against the spasm evoked by oxytocin (0.2 nM). The potency of salbutamol against the spasm evoked by KCl (80 mM) was modestly reduced (14 fold) compared to that against the spasm evoked by oxytocin (0.2 nM). The potency of nifedipine against the KCl (80 mM)-evoked spasm was not different from that against the oxytocin (0.2 nM)-evoked spasm. 5. The potencies of relaxin and levcromakalim against the spasm evoked by oxytocin (20 nM) + nifedipine (500 nM) were greatly reduced (74 fold and 234 fold respectively) compared to their potencies against the spasm evoked by oxytocin (0.2 nM). The potency of salbutamol against these two spasmogens was not different. 6. Relaxin was much less potent against the spasm dependent upon intracellular Ca2+ (that induced by oxytocin (20 nM) + nifedipine (500 nM)) than against the spasms dependent upon extracellular Ca2+, those induced by oxytocin (0.2 nM) and Bay K 8644 (1 microM). In this regard, relaxin resembled levcromakalim and nifedipine rather than salbutamol. Therefore, the major site of action of relaxin appears to be located at the plasma membrane rather than at an intracellular level. The observation that relaxin was less effective against the KCl (80 mM)-induced spasm than against the oxytocin (0.2 nM)-evoked spasm may indicate that relaxin has a minor action involving K(+)-channel opening. 7. High concentrations of relaxin (up to 1 microM) induced significant inhibition of the spasm dependent upon intracellular Ca2+. Thus at high concentrations relaxin also appears to have an additional intracellular action.
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Affiliation(s)
- S J Hughes
- Smooth Muscle Pharmacology Group, School of Biological Sciences, University of Manchester, Oxford
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17
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Affiliation(s)
- R A Cohen
- Robert Dawson Evans Department of Clinical Research, Boston University School of Medicine, Mass, USA
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18
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Criddle DN, Jazbik W, de Moura RS. Differential vasorelaxant effects of levcromakalim and P1060 in the isolated KCl- and RbCl-precontracted human saphenous vein: possible involvement of intracellular Ca2+ stores. Eur J Pharmacol 1995; 286:123-30. [PMID: 8605948 DOI: 10.1016/0014-2999(95)00426-l] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The influence of rubidium-substituted physiological salt solution (Rb-PSS) on the relaxant effects of K+ channel openers was investigated in the human saphenous vein. In tissues precontracted with 20 mM KCl (in K-PSS) levcromakalim and P1060 produced complete, sustained relaxations. However, in Rb-PSS (containing 20 mM RbCl) these effects were inhibited and, although complete relaxations still occurred, were transient. When caffeine was applied at the beginning of this fade of levcromakalim-induced relaxation in Rb-PSS its contractile effect was potentiated. Similarly, the contraction to noradrenaline was potentiated when applied at the beginning of this fade of levcromakalim-induced relaxation, whereas this response was attenuated in control tissues bathed in 20 mM KCl (in K-PSS). Our results show that the relaxant effects of K+ channel openers in human saphenous vein are inhibited in Rb-PSS, in agreement with previous studies in animal tissue, and suggest that an increased Ca2+ uptake into intracellular stores may be contributory to vasorelaxation.
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Affiliation(s)
- D N Criddle
- Departamento de Farmacologia, Universidade do Estado do Rio de Janeiro, Brazil
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19
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POSTER COMMUNICATIONS. Br J Pharmacol 1995. [DOI: 10.1111/j.1476-5381.1995.tb16904.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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20
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Poster Communications. Br J Pharmacol 1995. [DOI: 10.1111/j.1476-5381.1995.tb17201.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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21
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POSTER COMMUNICATIONS. Br J Pharmacol 1995. [DOI: 10.1111/j.1476-5381.1995.tb16307.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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22
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Abstract
The potassium-channel openers comprise a large number of molecules that can be classified into three basic groups: (1) agents like levcromakalim that open a small-conductance (10-30 pS) glibenclamide-sensitive K+ channel currently known as the ATP-sensitive K+ channel, KATP; (2) hybrid molecules, such as nicorandil, that open KATP channels and that also activate the enzyme-soluble guanylate cyclase; (3) molecules like dehydrosaponin 1 that open the large-conductance (100-150 pS) calcium-dependent K+ channel, BKCa. K(+)-channel openers in groups 1 and 2 are most potent on smooth muscle, but KATP channels in cardiac muscle, neurones and the pancreatic beta cell are also affected. In vivo, moderate to high doses produce a fall in diastolic pressure with reflex tachycardia; low doses may exert selective dilator effects on specific vascular beds with little effect on systemic pressure. In vitro, all smooth muscles are relaxed with loss of spontaneous electric and mechanical activity; hyperpolarization to the region of EK is often observed. These effects can be antagonized by glibenclamide and also by imidazolines and guanidines, such as phentolamine, guanethidine, and antazoline, agents that also inhibit the smooth muscle delayed rectifier channel, KV. The mode and site of action of the group 1 and 2 K(+)-channel openers is the subject of intense study. Irrespective of their specific mode of action, the K(+)-channel openers, especially the hybrid molecules such as nicorandil, constitute a novel and promising approach to the treatment of cardiovascular disease.
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Affiliation(s)
- G Edwards
- Smooth Muscle Pharmacology Research Group, School of Biological Sciences, University of Manchester, UK
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23
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Criddle DN, de Moura RS. Inhibitory effects of Rb+ on the responses to levcromakalim and P1060 in the isolated human myometrium. Eur J Pharmacol 1995; 272:293-6. [PMID: 7713174 DOI: 10.1016/0014-2999(94)00706-d] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The mechanoinhibitory effects of two structurally dissimilar K+ channel openers, levcromakalim and P1060, and verapamil were compared in strips of human myometrium bathed in either K-PSS (normal Krebs solution) or Rb-PSS (K+ salts replaced by Rb+ equivalents). In Rb-PSS the effects of levcromakalim and P1060 on amplitude and frequency of spontaneous contractions were inhibited by more than 20- and 138-fold, respectively, whereas those of verapamil were unaltered. These results indicate that K+ channel openers possess Rb-sensitive and Rb-insensitive mechanoinhibitory actions on the human uterus, the former being more important in the effects of P1060 than levcromakalim.
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Affiliation(s)
- D N Criddle
- Departamento de Farmacologia, Universidade do Estado do Rio de Janeiro, Brazil
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24
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POSTER COMMUNICATIONS. Br J Pharmacol 1994. [DOI: 10.1111/j.1476-5381.1994.tb16303.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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25
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Calder JA, Schachter M, Sever PS. Vasorelaxant actions of 5-OH-indapamide, a major metabolite of indapamide: comparison with indapamide, hydrochlorothiazide and cicletanine. Eur J Pharmacol 1994; 256:185-91. [PMID: 8050469 DOI: 10.1016/0014-2999(94)90244-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
5-OH-Indapamide is a principal metabolite of indapamide, and possesses similar antihypertensive and diuretic properties. This study investigated the mechanisms of the acute vasodilator actions of 5-OH-indapamide, indapamide, hydrochlorothiazide and cicletanine and their interaction with ion channels in isolated guinea pig mesenteric arteries. Hydrochlorothiazide, cicletanine and 5-OH-indapamide relaxed noradrenaline-constricted vessels significantly more than K(+)-constricted vessels (P < 0.001) and the relaxations were reduced in the presence of charybdotoxin (P < 0.001). 5-OH-Indapamide-induced relaxation was reduced (by 42% at 30 microM) by glibenclamide (P < 0.001). Hydrochlorothiazide, cicletanine and 5-OH-indapamide (all at 10 microM) were weak Ca2+ antagonists shifting the Ca2+ dose-response curves half a log unit to the right (P < 0.01). Indapamide was a more potent inhibitor, a 10 microM concentration shifting the Ca2+ dose-response curve three log units to the right and reducing maximal-induced Ca2+ contraction by 72% (P < 0.001). Hydrochlorothiazide, cicletanine and 5-OH-indapamide-induced relaxations appear to be partly mediated via Ca(2+)-activated K+ channels; 5-OH-Indapamide-induced relaxation is also partly mediated via ATP-sensitive K+ channels. Indapamide is a potent Ca2+ antagonist.
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Affiliation(s)
- J A Calder
- Department of Clinical Pharmacology, St. Mary's Hospital Medical School, Imperial College of Science, Technology and Medicine, London, UK
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26
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Criddle DN, Greenwood IA, Weston AH. Levcromakalim-induced modulation of membrane potassium currents, intracellular calcium and mechanical activity in rat mesenteric artery. NAUNYN-SCHMIEDEBERG'S ARCHIVES OF PHARMACOLOGY 1994; 349:422-30. [PMID: 8058114 DOI: 10.1007/bf00170890] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
In freshly-dispersed cells from rat mesenteric artery, levcromakalim (1 and 10 microM) induced a non-inactivating potassium current (IKCO), an event which was associated with increased current noise. IKCO was fully inhibited in the presence of 10 microM glibenclamide. Stationary fluctuation analysis of the current noise associated with IKCO induced by levcromakalim at a holding potential of -10 mV indicated that the unitary conductance of the underlying K-channels was 10.2 pS at 0 mV under the quasi-physiological conditions of the experiment. In isolated arterioles both levcromakalim (10 nM-10 microM) and nifedipine (10 nM-10 microM) each elicited full, concentration-dependent, parallel reductions of the increases in [Ca2+]i (assessed using fura-2) and tension induced by 10 microM noradrenaline. However, the effects of both drugs on KCl-induced increases in tension and in [Ca2+]i, did not follow a simple relationship. Levcromakalim relaxed KCl- and noradrenaline-induced sustained contractions with a similar potency. This was in contrast to nifedipine which was approximately 20 times more potent against KCl-induced contractions. It is concluded that levcromakalim relaxes rat mesenteric arterioles primarily by the opening of a small conductance, glibenclamide-sensitive K-channel. An additional action of levcromakalim is suggested by its relative inability to suppress the increase in [Ca2+]i produced by 30 mM K(+)-PSS.
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Affiliation(s)
- D N Criddle
- School of Biological Sciences, University of Manchester, UK
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27
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Abstract
During the past decade, a group of chemically heterogeneous compounds known as the K+ channel openers has emerged. These compounds open a certain class of K+ channels (ATP-sensitive K+ channels) in the sarcolemma of vascular smooth muscle cells, which leads to hyperpolarization of the cell membrane and relaxation of the tissue. The mechanisms by which hyperpolarization affects smooth muscle contraction and contractility can thus be examined. Hyperpolarization induced by these K+ channel openers prevents Ca2+ entry through voltage-operated Ca2+ channels. Surprisingly, and by mechanisms not yet defined, hyperpolarization of the cell also reduces agonist-induced accumulation of inositol 1,4,5-trisphosphate (and consequently, Ca2+ mobilization from intracellular stores), and the Ca2+ sensitivity of the contractile apparatus. In addition, recent evidence reviewed here by Ulrich Quast suggests that the K+ channel openers possess further mechanisms of vasorelaxation not linked to the opening of plasmalemmal K+ channels.
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Affiliation(s)
- U Quast
- Department of Pharmacology, University of Tübingen, Germany
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