Effect of exogenous phospholipase A 2 and triacylglycerol lipase on the synthesis and release of monoenoic and bisenoic prostaglandins from isolated rat uterus

• Published in: Prostaglandins, leukotrienes and essential fatty acids Vol. 44; no. 4; pp. 211 - 215
• Main Authors: Chaud, M.A., Franchi, A.M., Viggiano, M., Gimeno, A.L., Gimeno, M.A.F.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 1991
• ISSN: 0952-3278; 1532-2823
• DOI: 10.1016/0952-3278(91)90019-2

The possible existence of a selective and independent mechanism subserving the formation of prostaglandin E 1 (PGE 1) and of prostaglandin E 2 (PGE 2) has been reported in previous studies from our group. In the present experiments we have demonstrated that neutral lipid lipases play an important role yielding dihomo-gamma-linolenic acid for the formation of PGE 1. Indeed, exogenous triglyceride lipase added to the incubation bathing solution at a concentration of 150 U/ml increased several fold the production of PGE 1 by isolated uterine strips obtained from spayed rats. Nevertheless the presence of the enzyme did not modify significantly the synthesis and release of bisenoic PGs (PGE 2 and PGF 2α). When triarachidonin was added, as an artificial substrate into the incubating medium in order to detect the presence of endogenous triacylglycerol lipase, we observed a significant increment in the generation of PGE 2 (p < 0.005) and of PGF 2α (p < 0.001) without evident changes in the basal release of PGE 1. On the other hand, the addition of phospholipase A 2 (PLA 2) at 0.2 U/ml, increased significantly the production of PGE 2 (p < 0.001) but failed to alter the concentration of PGE 1 in the incubating solution. Surprisingly, PLA 2 did not enhance the synthesis of PGF 2α in the present experiments, a situation for which we do not have a clear explanation. Exogenous bradykinin (10 −6 M), a well known stimulant of PLA 2 activity in several tissues, also increased significantly (p < 0.001) the production of PGE 2 without altering that of PGE 1. Results presented herein provide strong support to the notion that different enzyme mechanisms and different lipid stores are linked to the formation of PGE 1 and PGE 2 in isolated rat uteri.