Abstract
By finding a suggestive evidence that Ca repletion in the junctional sarcoplasmic reticulum(JSR) occurs with a common JSR Ca content vs. time relationship after various degrees of JSR Ca release, we developed a method to estimate a time course of JSR Ca repletion after JSR Ca release and JSR Ca release/content relation by analyzing short-term mechanical restitution in papillary muscle of murine hearts (Tameyasu et al, Jpn J Physiol, 2004). Using this method, we could characterize the SR function in heart muscle of hypertensive rat and diabetic mouse, as reported recently. Applicability and limitation of our method was further tested in the present study. We show here that (1) there are little differences in a time course of JSR Ca repletion nor relation between the JSR Ca release and content as examined with papillary muscles among several different strains of mice, (2) the Ca handling property of the JSR obtained with whole heart preparation is similar to that with papillary muscle in mouse, (3) our method is applicable to analyze the JSR function under a low external Ca concentration, and (4) addition of caffeine (0.5 mM) violates a basic assumption that the JSR Ca repletion occurs with a common JSR Ca content vs. time relationship after various degrees of Ca release. The result ascertains that our method is quite useful to assess the JSR function at least in murine hearts. Analysis of the JSR function in rabbit heart with our method is in progress. [J Physiol Sci. 2007;57 Suppl:S205]
