Atrial specific granules: The intracellular calcium store

It is well known that certain organells in cytosol contain high calcium concentration and they are named intracellular Ca stores. These stores regulate the intracellular Ca concentration. The present project aims at exploring whether the release of atrial natriuretic peptide (ANP) from the atrial specific granules(ASG) is dependent on the release of calcium from the ASG. For this purpose, we have to know first whether the ASG contain high Ca concentration. In this work, positive results were obtained by quantitative electron probe x ray microanalysis (EPMA) and Ca-ATPase cytochemical localization.Adult female Sprague Dawley rats were used. The auricle samples were prepared in five different procedures: 1 )preparation of routine ultrathin sections; 2)ethanolic phosphotungstic acid(EPTA) staining ultrathin sections for ASG showing; [1] 3) cytochemical localization of Ca-ATPase ;[2] 4) preparation of ultrathin cryosections of fresh rapid frozen auricles; [3] 5) quantitative EPMA with Link AN10000 and Link Quantem/FLS quantitative analysis software.