Effects of resting membrane potential and intactness of the T-tubules on caffeine contractures in rat skeletal muscle |
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| Authors: | B A Kotsias C A Obejero Paz S Muchnik |
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| Institution: | 1. Pushchino Scientific Center for Biological Research of the Russian Academy of Sciences, Institute for Biological Instrumentation, Institutskaya str., 7, Pushchino, Moscow Region 142290, Russia;2. Pushchino Scientific Center for Biological Research of the Russian Academy of Sciences, G.K. Skryabin Institute of Biochemistry and Physiology of Microorganisms, pr. Nauki, 5, Pushchino, Moscow Region 142290, Russia;3. Department of Molecular Medicine and USF Health Byrd Alzheimer''s Research Institute, Morsani College of Medicine, University of South Florida, Tampa, FL 33612, USA;1. Department of Biochemistry and Physiology, University of Oklahoma Health Sciences Center, OK, USA;2. Center for Geroscience and Healthy Brain Aging, University of Oklahoma Health Sciences Center, OK, USA;3. Stephenson Cancer Center, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA;4. Aging & Metabolism Research Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma, USA;5. Oklahoma City VA Medical Center, Oklahoma City, OK, USA;6. Harold Hamm Diabetes Center, University of Oklahoma Health Sciences Center, OK, USA;1. Department of Medicine, Division of Gastroenterology, Hepatology and Nutrition, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA;2. Department of Neurobiology, Center for Neuroscience and Center for Pain Research, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA |
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| Abstract: | We have studied the effects of changes in the resting membrane potential (Vm) and T-tubules on caffeine contracture (25 mM) elicited in rat soleus muscle in vitro at 34 degrees C. In high K]o (30-140 mM, K]o X Cl]o constant) caffeine contractures were reduced by about 40-50% and had a faster time course than in normal Krebs (K]o = 5 mM). Detubulation of the muscles by an osmotic treatment produces a reduction of about 30% in the caffeine contracture tension. Our results with high K solutions suggest a reduced sensitivity of the myofibrils to calcium released by caffeine. The effects of detubulation on caffeine contracture suggest that caffeine may have a direct effect on sarcolemma in addition to its well known action on the sarcoplasmic reticulum (SR). However, a depletion of the calcium content in the SR of depolarized muscle fibres as well as an anatomical damage produced by the osmotic treatment can not be ruled out as an explanation for the reduced caffeine contracture. |
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