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Title:Characterization of the sarcoplasmic reticulum calcium release channel in skeletal muscle
Author(s):Kwok, Wai-Meng
Doctoral Committee Chair(s):Best, Philip M.
Department / Program:Biophysics
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Biophysics, General
Abstract:The ability of myofilament space calcium to modulate the sarcoplasmic reticulum (s.r.) calcium release channel in skeletal muscle was investigated. Two different experimental techniques were used to study this phenomenon. Optical techniques were used to study the effect of myoplasmic calcium concentrations on s.r. calcium release in skinned (sarcolemma removed) single muscle fibers. Results showed an inactivating and an activating effect of myoplasmic calcium on the calcium release rate. As the myoplasmic calcium concentration was increased from pCa = 7.4, calcium release rates declined to a minimum at pCa = 6.9, where release was 78 $\pm$ 3% (mean $\pm$ s.e.m.) of control (pCa = 8.4). As myoplasmic calcium was increased beyond pCa = 6.9, release rates increased. Release rates at pCa = 6.1 and 7.4 were 126 $\pm$ 11% and 100 $\pm$ 3% of control, respectively.
Patch-clamp technique was used to characterize the s.r. calcium release channel. Single channel recordings of inside-out patches of extruded native s.r. membrane were made. Four distinct levels of 31 $\pm$ 3, 49 $\pm$ 2, 81 $\pm$ 2, and 128 $\pm$ 7 pS were observed (n = 9 patches) in equimolar 50 mM calcium. Multiple states were also observed under physiological conditions with calcium concentrations of pCa = 7.4, 6.9, or 6.1 in the pipette and 50 mM calcium in the bath solution. The channel was sensitive to ryanodine. At -20 mV, the addition of 1 $\mu$M ryanodine to the bath increased the open probability, P$\sb{\rm o}$, from 0.17 to 0.83. Possible modulatory effects of calcium and of phosphorylation were also investigated. When the s.r. membrane was prepared in submicromolar calcium concentrations (pCa = 7.4 and 6.9), the probability of obtaining patches with an active channel was drastically less than when the preparatory solution contained millimolar calcium. This inactivating effect of submicromolar calcium concentrations in the bath was removed by the addition of phosphatase.
Issue Date:1990
Rights Information:Copyright 1990 Kwok, Wai-Meng
Date Available in IDEALS:2011-05-07
Identifier in Online Catalog:AAI9026237
OCLC Identifier:(UMI)AAI9026237

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