Muscarinic Receptors in Chromaffin Cell Cultures Mediate Enhanced Phospholipid Labeling but Not Catecholamine Secretion

Abstract

The addition of either carbachol or muscarinic agonists to cultured bovine adrenal chromaffin cells results in a selective stimulation of phosphatidate (PhA) and phosphatidylinositol (PhI) labeling from 32Pi and [3H]glycerol that can be inhibited by the inclusion of atropine, but not d-tubocurarine. In contrast, increased catecholamine secretion is observed on the addition of carbachol or nicotinic agonists and is inhibited by d-tubocurarine but not by atropine. Added calcium is essential for catecholamine secretion but not for stimulated phospholipid labeling. Chelation of endogenous Ca2+ with EGTA does, however, inhibit the stimulated phospholipid labeling. These results suggest that stimulated phospholipid labeling in the bovine chromaffin cell and catecholamine secretion are separate and distinct processes.