The relationship between the incorporation of 32P into phosphatidic acid and phosphatidylinositol in rat parotid acinar cells

Abstract

Muscarinic and α-adrenergic stimulation of rat parotid acinar cells increases the turnover of phosphatidylinositol and phosphatidic acid. It is thought that this is initiated by hydrolysis of phosphatidylinositol, which would predict an increase in 32P incorporation into phosphatidic acid before phosphatidylinositol. We have demonstrated an increase in 32P incorporation into the former within 1 minute and into the latter by 2 minutes. The initial rapid rate of 32P incorporation into phosphatidic acid slows, and the 32P content reaches a steady state after 15 minutes. During the first 2 minutes after the addition of atropine to carbamylcholine stimulated cells, 32P is lost from phosphatidic acid, and an equal amount is gained by phosphatidylinositol, after which 32P incorporation equals that of the control. In cells prelabelled with 32P, carbamylcholine, in the presence of oligomycin stimulated the loss of 32P from phosphatidylinositol but had no effect on phosphatidic acid.