Prostaglandin e₂-induced release of lhrh into hypophysial portal blood

Prostaglandin E₂ (PGE₂) was infused into a lateral ventricle of adult male rats or infused into a hypophysial portal vessel. Intraventricularly administered PGE₂ stimulated the release of LH, FSH, and prolactin but not TSH. Intraventricular infusion of the control solution did not alter the basal release of any of these hormones. PGE₂ was found to be a potent stimulator of LH release, but larger quantities were needed to stimulate the release of FSH or prolactin. In addition, lateral ventricle infusion of 5 μg or 20 μg of PGE₂ stimulated a 2- to 3-fold increase in the concentration of LHRH in hypophysial portal plasma but did not affect LHRH levels in arterial plasma. PGE₂ infused into a hypophysial portal vessel at a rate of 0.167 μg/min for 30 min, or infusion of the control solution, resulted in similar changes in the concentration of FSH, LH, and prolactin in arterial plasma. The results of this investigation suggest that PGE₂ stimulates the release of gonadotropins in vivo by enhancing the release of LHRH. The portal vessel infusion studies do not support a direct stimulatory effect of PGE₂ on the pituitary gonadotrophs.