Characteristics of Action of Prostaglandins on Cyclic AMP Accumulation in Rat Anterior Pituitary Gland

Abstract

Prostaglandins (PGs) were found to lead to a marked stimulation of cyclic AMP accumulation in rat anterior pituitary gland in vitro in the following decreasing order of potency: [Formula: see text]. The effect of PGs is potentiated by theophylline. The stimulatory effect of PGs on cyclic AMP accumulation is already detected 2 min after the addition of 1 × 10−7 to 1 × 10−6 M PG E2 and its maximal effect is reached after approximately 30 min of incubation, with a progressive decrease toward basal cyclic AMP levels at later time intervals. Increased intracellular cyclic AMP concentrations are accompanied by an increased release of the nucleotide into the incubation medium. Complete removal of Ca2+ from the incubation medium by addition of EGTA was found to increase the stimulatory effect of PG E2 on cyclic AMP accumulation. The action of PGs on hormonal release and cyclic AMP accumulation support the hypothesis of a role of PGs in the mechanism of anterior pituitary hormone (particularly growth hormone) release.