Abstract
To clarify the on-off mechanism of gonadotropin synthesis and its release in the anterior pituitary gland, the anterior pituitaries of the male rat were cultured in vitro through a leuteinizing hormone-releasing hormone (LH-RH) stimulation and a washing sequence for the analysis of cyclic nucleotide and gonadotropins. After the first stimulation of gonadotrophs with synthetic LH-RH for 20 minutes and the removal of LH-RH by washing, the alteration of the gonadotropin release and its content in the anterior pituitaries were investigated for several hours. The data indicate that the primary stimu-lation by LH-RH to the gonadotrophs has no continuous effect on the gonado-tropin release and synthesis after washing and that LH-RH, primarily ad-ministered, does not change the responsiveness to the secondarily administered LH-RH. The experiments also showed that by the stimulation of LH-RH, adenosine cyclic 3', 5'-monophosphate (c-AMP) was accumulated in the an-terior pituitary cells, but that such high accumulation did not continue after washing, and gonadotropins were released and synthesized by the admin-istration of dibutyryl c-AMP and theophillin. It is suggested that the con-tinuous gonadotropin release and synthesis required the continuous LH-RH stimulation, which maintains an elevated c-AMP concentration in the rat anterior pituitary gland.
