[Physiological significance of the self-priming effect of LH-RH on the anterior pituitary glands].

To investigate the intracellular mechanisms of the self-priming effect of LH-RH on the anterior pituitary gland, the responses of pituitary and serum gonadotropins to two administrations of this decapeptide at a 60 min, interval were studied in male rats. A clearly recognized self-priming effect in male rats was significantly suppressed by the administration of RNA synthesis inhibitor. Although the pituitary LH content decreased significantly after the first administration, the content increased to the control level immediately before the second administration. This recovery was prevented by the administration of RNA synthesis inhibitor. In spite of the large second response, the rate of the second LH depletion was low. The number of secretory granules in gonadotrophs showed similar changes to the pituitary LH content. The dilatation of the Golgi apparatus was observable at 60 min. after the first administration. These results of rat experiments indicate that the second response includes the newly synthesized gonadotropins, and a clinical LH-RH two step test could be employed to evaluate both pituitary gonadotropin synthesizing and secreting functions.