Effect of pre-incubation with different concentrations of LH-RH on subsequent LH release caused by supramaximally active amounts of LH-RH; role of LH-RH-induced protein synthesis.

Anterior pituitary glands from intact diestrous female rats were incubated for two consecutive periods of 3 hours. During the first period various submaximally active amounts of luteinizing hormone-releasing hormone (LH-RH) were added to the media, whereas during the second period a supramaximally active concentration of LH-RH was present. When during the second incubation period protein synthesis was inhibited by cycloheximide, the amount of luteinizing hormone (LH) released during that period was positively correlated to the concentration of LH present during the first incubation period. This relationship was not seen when cycloheximide was absent, or when cycloheximide was present throughout both periods. Total LH was not affected by LH-RH; thus no effect of LH-RH on LH synthesis was observed. It is concluded that the amounts of protein synthesized by the pituitary glands in response to the different amounts of LH-RH during the first incubation period can constitute a limiting factor for the response to the supramaximally active amount of LH-RH added during the second incubation period.