兔膈肌肌浆网Ca^(2+)-ATPase活性及钙离子的转运

Ca^(2+)-ATPase activity and Ca^(2+) transport in sarcoplasmic reticulum of rabbit diaphragm

本文分别用定磷法测定兔膈肌SR Ca 2+ -APTase 活性、Fura-2 荧光法测定SR Ca 2+ 释放、摄取动力学和[ 3 H] -Ryanodine 与RyR 结合实验测定SR RyR 的量，分析其功能特性。 结果显示兔隔肌、心肌和骨骼肌SR Ca 2+ -APTase 活性分别为70.13 ±8.25、 41.25 ±6.25 和120.17± 17.03 m mol/L pi/mg 蛋白/h1 。膈肌的SRCa 2+ -APTase 活性显著高于心肌P<0.01 。但明显低于骨骼肌P<0.01； 膈肌SR Ca 2+ 释放量和摄取速度显著快于心肌（P<0.01），但明显低于骨骼肌（P<0.01）；膈肌SR RyR 同[ 3 H] Ryanodine 的最大结合值（Bmax）是0.78 ±0.05pmol/mg 蛋白，其解离常数（KD）是6.93 1.13nmol/L，分别位于心肌和骨骼肌范围内。本文认为膈肌Ca 2+ 释放单位、SR Ca 2+ -APTase 和SR Ca 2+ 释放摄取动力学分别具有心肌和骨骼肌的一些特征，其Ca 2+ 释放可能具有变构偶联和CICR 偶联两种形式，心肌型DHPR 亚型，RyR 3 和SERCA 2 a 的存在可能是膈肌ECC 依赖于细胞外Ca 2+ 的主要原因。

SR Ca2+-ATPase activities SR Ca2+release and uptake kinetic parameter and RyR binding test wererespectively measured in diaphragm muscle(DM)of rabbit via detecting inorganic phosphorus ion Fura-2 fluores- cence and [3H] Ryanodine.The results showed:(1)SR Ca2+ -ATPase activities were 70.13 8.25 in DM 41.25 6.25in cardiac muscle(CM)and 120.17 17.03mmol/L pi/mg protein/h in skeletal muscle(SK)respectively.SR Ca2+ -ATPase activities of DM was significant higher than that of CM (P<0.01)and significant lower than that ofSK(P<0.01);(2)the kinetics of Ca 2+release and uptake of DM were significant higher than that of CM(P<0.01)andsignificant lower than that SK(P<0.01);(3)the Bmax for [ 3H] -Ryanodine binding to RyR in SR of DM was 0.780.05pmol/mg protein KD value was 6.93 1.13nmol/L with Scatchard plot analysis which were respectively lo- cated between that of CM and SK.We considered that Ca2+ release unit SR Ca2+-ATPase and Ca2+release and uptake kinetic parameter in DM had some characters of that in CM and SK two kinds of model of Ca2+ release via both conformational changes of linked proteins and Ca2+ induced Ca2+release (CICR)might be presented in DM.The presentof the cardic DHPR isoform RyR 3 and SERCA 2 a might be the main reason that ECC of DM depended on Ca 2+inextraceller.