Prostaglandin-induced release of anterior pituitary hormones: Structure-activity relationships

Prostaglandins (PG’s) of the E, F, A, or B series were infused into a lateral ventricle of the brain of adult male rats, and the efficacy of each PG to stimulate the discharge of LH, prolactin, and TSH from the pituitary gland was determined. PGE₂, PGF₂α, and PGF₂αβ were found to be potent stimulators of LH release. The release was considerably less when PGE₁, PGF₁β, PGA₂ or PGB₂ was infused. The basal release of LH was not altered by infusion of PGF_lα, PGA₁, PGB₁, or the control solution. It is suggested that the cis double bond in the 5, 6 position and the 11-hydroxyl group are essential for the LH releasing activity of PG’s and that these functional groups may be of importance for activation of a receptor at the level of the brain. Prolactin secretion was stimulated 6 to 7-fold by the infusion of 5 γg of PGE₂, but 20 γg had no stimulatory effect. PGF₂β caused a 3 to 4-fold increase in basal plasma prolactin concentration and was the only PG tested other than PGE₂ that stimulated prolactin release. None of the PG’s infused intraventricularly affected TSH secretion.