Vasopressin Decreases Total Free Fatty Acids but Enhances Release of Radioactivity from Isolated Hepatocytes Labelled with [³H]Arachidonic Acid

Summary

The short-term effects of vasopressin on free fatty acids and lysophospholipids were investigated in hepatocytes isolated from fed rats. Over the time period 0.25 to 10 min vasopressin decreased the steady-state concentrations of palmitic, stearic and oleic acids measured by gas liquid chromatography in extracts of cells incubated at 0.1 mM extracellular Ca²⁺. The concentrations of arachidonic and linoleic acids did not change. In hepatocytes labelled with [³H]arachidonic acid and incubated at 1.3 mM extracellular Ca²⁺ vasopressin or the Ca²⁺-selective ionophore A23187 increased the rate of accumulation of radioactivity in the incubation medium by 40%. The action of A23187 was dependent on extracellular Ca²⁺. When hepatocytes labelled with ³²Pi were treated with vasopressin, no change in the amounts of [³²P]lysophosphatidylethanolamine or [³²P]lysophosphatidylcholine was observed. It is concluded that the action of vasopressin on hepatocytes is associated with the release of arachidonic acid or metabolites of arachidonic acid but is not accompanied by a general increase in the steady-state concentrations of free fatty acids and lysophospholipids.

Key-Words

Vasopressin - Arachidonic Acid - Lysophospholipids - Calcium - Isolated Hepatocytes