Colecystokinin octapeptide CCK-8 and carbachol reduce [³²P]orthophosphate labeling of phosphatidylcholine without modifying phospholipase D activity in rat pancreatic acini

We have studied phospholipase D activation in [32P]orthophosphoric acid-prelabeled rat pancreatic acini by measuring the formation of 32P-phosphatidylalcohols as stimulated in the presence of ethanol or butanol. A small but significant and time-dependent basal accumulation of [32P]phosphatidylethanol and [32P]phosphatidylbutanol was detected, which was further stimulated by phorbol myristate acetate, orthovanadate and pervanadate. However, the secretagogues cholecystokinin octapeptide and carbachol did not enhance basal accumulation of 32P-phosphatidylalcohol, yet they decreased [32P]phosphatidylcholine content and stimulated the generation of [32P]phosphatidic acid. Our results stress the need to examine the transphosphatidylation reaction as well as agonist effects on the synthesis of phosphatidylcholine in order to assess unambiguously phospholipase D activity. (C) 2000 Federation of European Biochemical Societies.