Inhibin-like effects of interstitial testis fluid: effects on serum FSH and androgen-binding protein in epididymis.

Application of rat interstitial testis fluid (ITF) to orchidectomized rats diminishes significantly the rise of FSH in serum following castration. The effect is seen for 12-24 hours on day 3 and 50 after orchidectomy but not at 48 hours in rats treated 50 days after orchidectomy. LH levels are not significantly affected. These observations are assumed to be related to an inhibin-like activity in ITF. Therefore ITF (after extraction with ether) is given to intact animals and the testicular parameter of FSH, the androgen-binding protein (ABP), is measured by "steady-state" PAGE. Unexpectedly, ABP concentrations increase. At present, this effect cannot be explained. It is concluded that ITF contains only small amounts of inhibin and will be no good source for further studies.