兔膈肌肌浆网Ca2+-ATPase活性及钙离子的转运

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。

Ca2+-ATPase activity and Ca2+ transport in sarcoplasmic reticulum of rabbit diaphragm

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.