Stimulation of Prostacyclin Production in Isolated Rat Adipocytes by Angiotensin II, Vasopressin, and Bradykinin: Evidence for Two Separate Mechanisms of Prostaglandin Synthesis*

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Abstract
The effects of 3 vasoactive peptides (angiotensin II, vasopressin and bradykinin) and norepinephrine on the production of prostaglandin I2 [prostacyclin (PGI2)] and PGE2 by isolated rat adipocytes were compared. Angiotensin II, vasopressin and bradykinin stimulated PGI2 production, but had minimal or no effect on PGE2 production or triglyceride lipolysis in isolated rat adipocytes, while norepinephrine stimulated PGI2 production, PGE2 production and triglyceride lipolysis. The arachidonic acid that serves as substrate for PGI2 production in adipocytes in response to the vasoactive peptides appears to be derived from the cellular phospholipids rather than the triglycerides in these triglyceride-laden cells. The adipocyte contains 2 separate mechanisms for PG production: a catecholamine-stimulated mechanism for the production of PGI2 and PGE2 that is activated concomitantly with triglyceride lipolysis, and a mechanism activated by vasoactive peptides for the stimulation of PGI2 production independent of triglyceride lipolysis and PGE2 production. These mechanisms may have distinct functions.