Studies on the structure and function of the mammalian testis V. Steroid metabolism by isolated interstitium and seminiferous tubules of the human testis

Abstract

Tissue was obtained from the testes of three men, two in the age range 72-75 years (subjects A and B) and one aged 25 years (subject C). Parts of the testes were dissected to obtain samples of interstitium and tubules. The individual components and whole tissue were each incubated with equimolar concentrations of [7 α - 3 H]pregnenolone and [4- 14 C]progesterone in Krebs-Ringer bicarbonate buffer pH 7.4, at 35 °C with the addition of glucose but without cofactors. Some incubations were carried out with the substrates [4- 14 C]androstenedione and [7 α - 3 H]testosterone. The media were extracted both at various time intervals throughout the incubation for a kinetic study of the metabolic activity and after a fixed interval of time at the end of the incubations. In some incubations with whole tissue both media and tissue were extracted. Both the tubules and interstitium displayed steroid metabolic activity. Qualitatively they yielded the same range of metabolites, one series leading to the formation of testosterone (∆ 5 pathway) and the other to a variety of C 21 compounds as represented by 5 α -pregnan-3 β -ol-20-one. With similar amounts of tissue there was little difference in the yields of the main products formed by the tubules as compared with those formed by the interstitium; in incubations with [4- 14 C]androstenedione the rate of conversion to [ 14 C ]testosterone by the tubules greatly exceeded that due to the interstitium. Marked differences were found in the pattern of steroid metabolism by whole tissue as compared to the general pattern presented by the corresponding tubules and interstitium. It is concluded that the seminiferous tubules and interstitium of the human testis are both capable of steroid metabolism and hence that whole tissue incubations alone are of limited value and could give rise to misleading data. Some clinical aspects of the results are briefly discussed.