Adrenal medulla calcium channel population is not conserved in bovine chromaffin cells in culture

Abstract

During the stress response adrenal medullary chromaffin cells release catecholamines to the bloodstream. Voltage-activated calcium channels present in the cell membrane play a crucial role in this process. Although the electrophysiological and pharmacological properties of chromaffin cell calcium channels have been studied in detail, the molecular composition of these channels has not been defined yet. Another aspect that needs to be explored is the extent to which chromaffin cells in culture reflect the adrenal medulla calcium channel characteristics. In this sense, it has been described that catecholamine release in the intact adrenal gland recruits different calcium channels than those recruited during secretion from cultured chromaffin cells. Additionally, recent electrophysiological studies show that chromaffin cells in culture differ from those located in the intact adrenal medulla in the contribution of several calcium channel types to the whole cell current. However there is not yet any study that compares the population of calcium channels in chromaffin cells with that one present in the adrenal medulla. In order to gain some insight into the roles that calcium channels might play in the adrenal medullary cells we have analyzed the α 1 subunit mRNA expression profile. We demonstrate that the expression pattern of voltage-dependent calcium channels in cultured bovine chromaffin cells markedly differs from that found in the native adrenal medulla and that glucocorticoids are only partially involved in those differences. Additionally, we show, for the first time, that the cardiac isoform of L-type calcium channel is present in both bovine adrenal medulla and cultured chromaffin cells and that its levels of expression do not vary during culture.