The follicle stimulating hormone-inhibin feedback loop in male primates

Application of an enzyme immunoassay for urinary follicle-stimulating hormone to describe the effects of an acute stressor at different stages of the menstrual cycle in female laboratory macaques

An enzyme-linked immunosorbent assay (ELISA) for human urinary beta follicle-stimulating hormone (FSH) subunit was validated for use in the laboratory macaque (Macaca mulatta and Macaca fasicularis). This ELISA is based on the dissociation of the FSH heterodimer in urine and the subsequent measurement of the beta subunit as a representation of total urinary FSH. This assay was then used to describe the gonadotropin escape following ovarian senescence in post-menopausal macaques. In addition, the assay was used to observe the impact of an acute stressor on the pituitary-gonadal axis and how the impact of this stressor varies when experienced at different stages of the menstrual cycle. The study design involved the measurement of ovarian steroids and FSH in urine collected daily during a period of time when animals experienced a well-defined event on two occasions consisting of capture, restraint, and anesthesia. This unique study design was made possible by the ability to monitor both ovarian and pituitary function in the absence of confounding daily captures and restraint for blood collection. There was a high correlation between urinary FSH measured in macaques with the beta FSH subunit ELISA and serum FSH measured in paired blood samples by radioimmunoassay (n=39, r2=0.878, P<0.001) and the composite urinary FSH profile obtained from normal, premenopausal macaques exhibited the expected dynamics with a transient rise of FSH during the luteal-follicular transition as well as an acute rise of FSH at mid-cycle. This pattern was lost in castrate and post-menopausal monkeys in which FSH levels were significantly increased (P<0.0001) above those of intact males and young females, respectively. In the stress study, we found that stressors occurring during the luteal-follicular transition not only resulted in acute perturbations of FSH but also led to abnormalities in the subsequent menstrual cycle in 50% of the cases.

Tissue-specific expression of inhibin/activin subunit and follistatin mRNAs in mid- to late-gestational age human fetal testis and epididymis

Inhibin/activin subunit (alpha, beta A, and beta B) immunoreactive protein localization patterns and cell type specific inhibin alpha-subunit mRNA expression have been examined in early- to midgestational age human fetal testes. The scarcity of available third trimester human fetal tissue has, however prevented a complete examination throughout the gestational period and the cell specific expression of follistatin and beta A- and beta B-subunit mRNAs are currently unknown at any gestational age. In the present study, this gap is filled and report mRNA expression patterns of inhibin/activin subunits in mid- and late-gestational age (21-33 wk) human fetal testes and testicular duct system. We also report the first examination of follistatin mRNA signals in the human fetal gonad is also resent in both tubular and interstitial cells, and beta B-subunit mRNA is expressed in seminiferous tubules, in mid- and late-gestational age human fetal testes. Inhibin/activin beta A-subunit mRNA was detected in the interstitial cells of remarkably well preserved mid (21 and 22 wk) and late (29 wk) gestational age testes, and is the only activin-system factor mRNA also expressed in tissue of the duct system of the testis (smooth muscle cells of the epididymis). Follistatin mRNA signal was equal to background levels in testicular and duct tissues at all ages examined. These cell specific expression patterns suggest prominent and possibly differential roles for the inhibins and activins, unopposed by gonadal follistatin, in the human fetal male reproductive system.