Effects of pure FSH and LH preparations on the number and function of Leydig cells in immature hypophysectomized rats

The effects of pure FSH and/or LH preparations on the number of Leydig cells and their function in immature hypophysectomized rats have been investigated. As a result of hypophysectomy at the age of 17-18 days, the number of recognizable Leydig cells per testis decreased, as did the steroidogenic capacity in vivo and in vitro. Treatment with 64 micrograms FSH on both 22 and 23 days of age, did not affect the number of recognizable Leydig cells. In contrast, two injections of LH (10 micrograms) caused a sixfold increase in the number of Leydig cells, but had a negative effect on spermatogenesis. These stimulatory and inhibitory effects of LH diminished when FSH was added. Treatment with FSH for 7 days caused a twofold increase in the number of Leydig cells when compared with hypophysectomized controls. 3 beta-Hydroxysteroid dehydrogenase (3 beta-HSD) and esterase activity in Leydig cells also increased under the influence of FSH. The pregnenolone production per Leydig cell in the presence of 5-cholesten-3 beta,22(R)-diol (22R-hydroxycholesterol) as substrate showed a sevenfold increase. Plasma testosterone levels 2 h after injection of human chorionic gonadotrophin in intact rats and hypophysectomized FSH-treated rats were the same. Following LH treatment for 7 days, the number of Leydig cells proved to be 11 times higher, and 3 beta-HSD and esterase activity were not different from intact controls. The testicular pregnenolone production was four- to fivefold higher when compared with untreated hypophysectomized rats. However, pregnenolone production per Leydig cell in LH-treated rats was only slightly different from the hypophysectomized controls.(ABSTRACT TRUNCATED AT 250 WORDS)