Feedback Control by the Testis of Gonadotrophin Secretion: An Examination of the Inhibin Hypothesis

Abstract

Spermatogenesis in rats was interrupted by local X-irradiation, heat or ligation of the testicular efferent ducts. A significant and specific rise in the serum level of FSH occurred 5--8 days after ligation of the efferent ducts, reaching twice the value observed in sham-operated controls by 21 days after the operation. After the testes were heated to 43 degrees C for 30 min, the serum levels of both LH and FSH were raised within 3 days and remained so up to 50 days after treatment. After X-irradiation, no changes in the concentration of FSH were observed in the first 21 days after treatment, but the serum levels of both gonadotrophins were increased at 49 days. By comparing the relative increases in the concentrations of FSH and LH after germ cell damage with those occurring after castration, it was evident that testicular androgens could account for only part of the normal feedback control of FSH secretion; at least one third of the inhibition of FSH secretion appeared to be due to non-androgenic sources, presumably 'inhibin'.

A chimaeric calf with XX/XXY mosaicism and intersexuality

“…The concentrations of testosterone in the blood were measured by the radioimmunoassy method of Main, Davies & Setchell (1978). The specificity of the testosterone assay relative to testosterone (100%) was only significant with respect to two other androgens: dihydrotestosterone (52-0%) and 5a-androstan-3a,17ß-diol (34-4%).…”

Effect of an acute exposure of rat testes to gamma rays on germ cells and on Sertoli and Leydig cell functions

“…However, the same authors have observed that the decrease in testicular blood flow induced by irradiation can lead to a slight decrease in the total amount of testosterone entering the general circulation. In the present study in which y rays were used in the same way as X-rays in previous studies (Hopkinson et al, 1978;Main et al, 1978;Delic et al, 1986) (Delic et al, 1986), but has more often been considered to result from the changes induced in the cell-to-cell interactions between the seminiferous tubules and the interstitial compartment (Risbridger et al, 1981 b).…”

“…Spermatogonia are known to be the most radiosensitive cells in the testis, but if the radiation dose is higher, more differentiated cells can also be destroyed (Shaver, 1953;Oakberg and Di Minno, 1960 Huckins, 1978;Hopkinson et al, 1978;Main et al, 1978;Wang et al, 1983;Pinon-Lataillade et al, 1985;Delic et al, 1986;Kamtchouing et al, 1988;Pineau et al, 1989 (Parvinen, 1982; Sharpe, 1986;J6gou et al, 1988;Verhoeven and Cailleau, 1989 (J6gou et al, 1988). One possible approach to the investigation of this complex aspect of the paracrine regulation of spermatogenesis has been to use different protocols of irradiation which, in vivo, were found to induce different degrees of seminiferous epithelium modification (Rich and De Kretser, 1977;Hopkinson et al, 1978;Vihko et al, 1984;PinonLataillade et al, 1985PinonLataillade et al, , 1988Pineau et al, 1989;Kangasniemi et al, 1990a, b).…”

Effect of scrotal insulation on the pituitary--testicular axis of the ram

“…Several earlier investigations into the hormonal changes that accompany injury to the testes have demonstrated considerable variation in the concentrations of LH and testosterone (Collins et al, 1978 ;Main et al, 1978). Because of this variation, quite large changes in mean values obtained for these hormones are sometimes dismissed as being insignificant.…”