Depolarization-induced Calcium Release from Sarcoplasmic Reticulum Fragments

Publisher Website
Google Scholar
Abstract
Ca2+ incorporated in vesicles of sarcoplasmic reticulum fragments (SRF) by diffusion could be released rapidly by changing the ionic environment, by dilution from methanesulfonate (MS) to chloride. This ion exchange is considered to make the membrane potential of SRF inside-negative. Much faster release of Ca2+ was also observed upon osmotic change from high to low. These responses were very similar to the Ca2+ release from SRF after take up using ATP, but the release rate was slow in the case of anion exchange. The behavior of K+, Na+, sucrose, and inulin incorporated in SRF was followed upon similar treatment. These ions and molecules were not released upon ion exchange, but were immediately released by osmotic treatment. Therefore, the Ca+ release upon anion exchange was not due to the bursting of SRF, but to a direct effect such as a membrane potential change of the SRF. The behavior of anions such as Cl− and propionate could not be followed by the same method because of the large permeability of these anions. It was also shown that Ca+ release upon ion exchange was not a direct effect of pH change. Liver microsomes did not show Ca+ release upon the same treatment as SRF2

This publication has 1 reference indexed in Scilit: