GnRH action in rat anterior pituitary gland: regulation of protein, glycoprotein and LH synthesis.

The effect of synthetic GnRH on the synthesis of proteins and glycoproteins in the anterior pituitary and in vitro release of LH into the medium was studied. A maximal dose (25 ng/ml) of of synthetic GnRH caused optimum release of radioimmunoassayable LH into the medium after 2 h of incubation. A concomitant increase in cyclic AMP accumulation in the tissue and LH in the incubation medium was also observed under the influence of GnRH during different periods of incubation time. Incubation of the rat anterior pituitary with GnRH stimulated the incorporation of [3H] proline into acid precipitable proteins in a time- and dose-dependent manner, similar to radioimmunoassayable LH released into the medium. Similar results were obtained when pituitary was incubated with dibutyryl cyclic AMP. LH, in addition, enhanced the incorporation of [3H] glucosamine and [3H] amino acids mixture into acid-precipitable proteins suggesting that proteins including glycoproteins are synthesized by the rat anterior pituitary under the influence of GnRH. Approximately 10% of the radioactivity associated with proteins comigrated with radioimmunoassayable LH on the gels. GnRH also enhanced the incorporation of [3H] glucosamine and [3H] amino acid mixture into immunoprecipitable LH. The GnRH-induced incorporation of [3H] proline into anterior pituitary proteins was abolished by specific translation inhibitors.