CALYCULIN-A BLOCKS BOVINE CHROMAFFIN CELL CALCIUM CHANNELS INDEPENDENTLY OF PHOSPHATASE INHIBITION

The specific phosphatase inhibitor, Calyculin-A (CL-A), decreases high -K stimulated catecholamine secretion in bovine chromaffin cells. This effect can be split into two components: one needs long exposures to the drug to be elicited, and is sensitive to the protein kinase-inhibi tor K252a; the other is observed after short incubations of CL-A, and is insensitive to K252a. Here we report that the latter component is d ue to an external block, by CL-A, of chromaffin cell calcium channels in a voltage-dependent, reversible and phosphorylation-independent man ner.