Stimulation of anterior pituitary prostaglandin E content and somatotropin (growth hormone) synthesis by phospholipase A.

The prostaglandin E content of dispersed rat anterior pituitary glands was found to increase in the presence of phospholipase A or arachidonic acid. The increases were abolished by the addition of indomethacin. Similarly, the rate of somatotropin (growth hormone) synthesis was increased by these two agents, and the increases were again abolished by indomethacin. Phospholipase A also stimulated somatotropin release. The stimulation of prostaglandin E accumulation was a specific response to those fatty acids that are precursors for prostaglandin synthesis. One such precursor, [3H]arachidonic acid, was incorporated by rat anterior pituitary glands in vitro, and found to be associated mainly with phosphatidylethanolamine-like material. It is concluded that the intracellular concentration of prostaglandin E is limited by the availability of precursor fatty acids and that this can be increased by the addition of exogenous precursors or by the action of exogenous phospholipase A on the cellular phospholipid. Factors that increased prostaglandin E concentrations also increase the rate of synthesis of somatotropin, providing further evidence for the concept that prostaglandin E is involved in modulation of the rate of synthesis of this hormone.