Effect of gonadectomy on pituitary levels of mRNA encoding gonadotropin subunits and secretion of luteinizing hormone.

Using cell-free translation of pituitary mRNAs we have investigated how, following gonadectomy in rats, the translational capacity of the specific messages encoding precursors to gonadotropin subunits alpha, LH-beta and FSH-beta increases with time. In parallel, serum LH was assayed in order to compare release and synthesis patterns. We observed a rapid rise in the rate of synthesis of all three precursors, with a significant increase already detectable 4 days after gonadectomy, and a plateau reached after 21 days. The kinetics were similar in both males and females, but maximal translational values for alpha-subunit were slightly higher in males. During the same time period, serum LH rapidly increased in the males, while in the females the rise of circulating LH was somewhat delayed. Although no direct correlation seems to exist between synthesis and release processes of gonadotropins, it is evident from our previous findings and the present data that both phenomena are dependent on gonadal steroids. In this respect, estradiol has been shown to regulate negatively, via different routes, the synthesis as well as the secretion of pituitary gonadotropins.