Cholinergically stimulated phosphatidylinositol breakdown in parotid-gland fragments is independent of the ionic environment

Abstract

Carbamoylcholine stimulated phosphatidylinositol breakdown in rat parotid-gland fragments incubated in either a Krebs-Ringer medium or an ion-depleted iso-osmotic sucrose medium. This suggests that phosphatidylinositol breakdown is not initiated by a change in the intracellular concentration of Na+ or of K+, and previous experiments have indicated that it is independent of cyclic nucleotides and Ca2+. This reaction may be initiated by a direct interaction at the plasma membrane between the activated muscarinic cholinergic receptor system and the enzyme that catalyzes phosphatidylinositol breakdown.