Biphasic rise caused by extracellular ATP in intracellular calcium concentration in bovine adrenocortical fasciculata cells

Abstract

We examined the effect of extracellular ATP on intracellular calcium concentration ([Ca 2+] i) in bovine adrenocortical fasciculata cells. The suspended cells and the monolayer cells on coverslips were loaded with fura2. We found that ATP caused a rapid transient rise [Ca 2+] i in dose-dependent manner in the presence of extracellular Ca 2+ and that the rise in [Ca 2+] i caused by ATP was biphasic. We did not observe the second phase in the absence of extracellular Ca 2+. These results suggest that the first rise in [Ca 2+] i caused by ATP is due to Ca 2+ release from intracellular Ca 2+ stores and subsequent rise due to Ca 2+ influx across the plasma membrane. Furthermore, we found that the first phase of the monolayer cells consisted of two peaks. So it is possible that Ca 2+ release from intracellular Ca 2+ stores caused by ATP is induced by two different manners in adrenocortical fasciculata cells. In addition, monolayer cells are more useful than suspended ones in the examination of Ca 2+ mobilization in adrenocortical fasciculata cells.