RNA synthesis in Leydig cells during sexual maturation in the rat: effect of LH

The trophic action of LH on Leydig cells involves the triggering of a number of cellular events including changes in protein synthesis. This latter change has led a number of workers to postulate an effect of LH on RNA synthesis. A direct action of LH on RNA synthesis, however, has been difficult to assess. The aim of the present work was to analyse the effect of LH on RNA synthesis in vitro during sexual development. Studies were performed using purified Leydig cells from rats of 20, 30, 40, 50, 60 and 90 days of age. The results obtained show that basal uridine incorporation into RNA increases in an age-dependent manner in rats from 20 to 60 days of age and then remains unchanged until 90 days of age. A stimulatory effect of LH on RNA synthesis was clearly demonstrated only in the youngest rats (20 and 30 days old). In order to differentiate the effect of LH on different RNA populations, the RNA synthesized by immature and mature rats was analysed using a poly(U)-Sepharose column. In 20-day-old rats, LH stimulated both unbound and poly(A) RNA, although a more marked effect was clearly demonstrated on the latter. On the other hand, LH had an identical effect on both unbound and poly(A) RNA obtained from Leydig cells of 60-day-old rats. This stimulatory effect of LH on RNA synthesis in Leydig cells from immature rats seemed specific, since effectors which act on interstitial cells, such as LH-releasing hormone, [Arg8]-vasopressin and FSH (which may act on macrophages) did not modify RNA synthesis.(ABSTRACT TRUNCATED AT 250 WORDS)