CYTOCHEMICAL-LOCALIZATION AND CALCIUM QUANTITATION OF INTRACELLULAR CALCIUM STORE IN RAT ATRIAL CARDIOCYTES

Ethanolic phosphotungstic acid (EPTA) method and G-6-Pase method were used to localize cytochemically the atrial specific granules (ASG) and sarcoplasmic reticulum (SR) of rat atrial cardiocytes under the elect ron microscope, and at the same time, the calcium (Ca) in ASG and SR w as analyzed quantitatively by analytical electron microscopy (AEM). In these methods, the procedure of osmium tetroxide fixation was shorten ed or even abolished to keep more combined Ca. The Ca concentration in ASG and in the terminal cisterna of SR (TSR) was 64 +/- 16 and 99 +/- 21 mM/kg dry wt respectively. These values are approximate to those r eported in earlier works that were done on cryosections. It is suggest ed that these cytochemical methods could reserve a large part of combi ned Ca in the intracellular Ca store, and they are much simpler than t he low temperature techniques of biological specimen preparation. Ther efore, these methods are useful for AEM microanalysis of elements in o rganelles.