Stimulation of Luteinizing Hormone-Releasing Hormone Release from Perifused Hypothalamic Fragments by Phospholipase A2*

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Abstract
LHRH release is dependent on the availability of calcium, and prostaglandin E2 is a potent releaser of LHRH. Therefore, we investigated the role of phospholipase A2 (PLA2) on the release of LHRH from the hypothalamus. Four rat hypothalami were perifused with Krebs-Ringer buffer, and after a 60-min preincubation period, PLA2 was applied during 10 min. The LHRH response was determined by RIA of 10-min fractions collected for the next 60 min. PLA2 induced LHRH release in a dose-related manner at amounts of 2, 10, and 50 U. Omission of Ca++ from the medium using EGTA eliminated the PLA2 effect. Indomethacin treatment increased rather than diminished the PLA2 stimulation. Perifusion with melittin, an activator of PLA2, also increased LHRH release. These results are interpreted as a demonstration that PLA2 has a role in the release of LHRH and that a different route of the cyclooxygenase may be involved besides the well known mediation of prostaglandin E2.

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