Action of linoleic acid on phospholipase C activity at the rectal level of the African locust under the control of protein kinase C.

Linoleic acid (18:2n-6), linolenic acid and eicosatrienoic acid stimulated fluid reabsorption in locust rectum. Only 18:2n-6 was able to enhance phospholipase C activity, inositol(1,4,5) trisphosphate production and to increase cytosolic free Ca2+ concentrations in epithelial cells via the opening of L-type Ca2+ channels. These effects resemble those exerted by neuroparsin, an antidiuretic neuronal hormone extracted from the storage lobes of the locust corpora cardiaca. As for neuroparsin, the effects of 18:2n-6 were abolished after pre-treatment with the protein kinase C inhibitor, polymyxin B. The results were consistent with a regulation of neuroparsin-sensitive phospholipase C activity by 18:2n-6 under control of protein kinase C, possibly by increasing membrane fluidity. Cyclooxygenase inhibitors attenuated the effects of 18:2n-6. This demonstrated that the results should be produced via the metabolites of 18:2n-6 HODEs rather than the PUFA itself.