Müllerian-inhibiting activity of human fetal testicular tissue deprived of germ cells by in vitro irradiation.

Abstract

Extract: Fragments of testicular tissue from seven human fetuses were explanted in three organ-culture dishes for each fetus. One remained unirradiated while the others were submitted to, respectively, 500 and 700 rads of 6 0Co γ-rays. After an interval of 1–2 weeks, the mullerian-inhibiting activity of the explants was tested using the 14 0.5-day-old rat miillerian duct as end organ and the number of germ cells present in 50 orthogonal sections of seminiferous tubules was determined on a minimum of 10 histologic sections. In control explants, only 12.9% of the original number of germ cells were normal after 1–2 weeks in vitro. The mortality of germ cells was increased by γ-rays; only 7% of their original number surviving 500 rads, and 3% 700 rads. Mullerian-inhibiting activity of both control and irradiated explants was normal. Speculation: Mullerian-inhibiting activity of human fetal testicular explants is not affected either by in vitro survival or by γ-irradiation, although both these procedures significantly deplete the germ cell population of the seminiferous tubules, only 3% surviving exposure to 700 rads. If germ cells were involved in the secretion of the antimullerian hormone, such a drastic reduction of their number would certainly be reflected by an impairment of the mullerian-inhibiting activity of the irradiated explants. As this is not the case, and as it has been demonstrated previously that the antimullerian hormone is synthesized by seminiferous tubules and not by interstitial tissue, we speculate that Sertoli cells are the source of the hormone.