Gonadotropin-releasing hormone stimulates the synthesis of the polypeptide chains of luteinizing hormone.

The effect of GnRH on the synthesis of the polypeptide chains of LH was reevaluated using the incorporation of labeled methionine by pituitary cells in culture, followed by specific immunoprecipitation of LH-related subunits and sodium dodecyl sulfate-polyacrylamide gel analysis of immuno-precipitated peptides. Fluorography and counting of labeled subunits separated on the gels demonstrated that the presence of GnRH in the medium significantly enhanced the radioactivity incorporated into both alpha- and LH beta-subunits after a 5-h incubation period. Cycloheximide completely inhibited [35S]Met incorporation in the absence or presence of GnRH, whereas actinomycin D only prevented the stimulatory effect of GnRH on this incorporation. The increase of potassium ion concentration in the medium to 59 mM was without any effect on the synthesis of LH subunits. These data demonstrate that GnRH specifically stimulates synthesis of the polypeptide chains of LH and suggest that GnRH action is mediated by RNA synthesis. Whether the expression of specific messenger RNAs encoding the LH subunits is affected by GnRH is now under investigation.