In VitroResponse of the Rat Pituitary to Gonadotrophin-Releasing Factors and to Ions

Short-term incubations of rat anterior pituitary glands in Krebs-improved Ringer I (KR) media with varied concentrations of K+ showed that [K+] of 60 mm or more increased LH and FSH release from the glands, while with a [K+] of 30 mm the stimulatory effect was minimal. The effect of high [K+] on hormonal release was reversible, and there appeared to be an additive effect between high [K+] and releasing factors. The action of high [K+] on LH and FSH release was completely abolished in Ca++-free media, while the effect of releasing factors was only partially inhibited. EDTA-Na in Ca++-free media completely inhibited the effect of releasing factors. EDTA had some inhibitory effect on the action of LRF by a mechanism other than by immobilization of Ca++. High concentrations of Mg++ also inhibited the action of both high [K+] media and releasing factors, while Mg++-free media enhanced their action very slightly, which supports the important role of Ca++ in the secretory mechanism. Na-free Locke’s solution caus...