The combined effects of transient neonatal hypothyroidism and neonatal hemicastration were investigated to see whether they were additive. Hypothyroidism was induced in litters of ten male rats for 25 days from the day of birth by administration of 0.1% (w/v) 6-propyl-2-thiouracil in the mother's drinking water; hemicastration was performed on the day of birth. Controls included both normal and sham-operated animals. Numbers of Sertoli cells and round spermatids were quantified at age 135 days using stereological methods. Sham-operation had no effect on testis mass, or numbers of Sertoli or germ cells. Transient neonatal hypothyroidism resulted in an increase in testicular mass of 27% (P <0.05), whereas neonatal hemicastration resulted in a 33% (P <0.05) increase over control; the combination of the two procedures resulted in a 62% (P < 0.05) increase. There were corresponding significant increases in the number of Sertoli cells: 82% with hypothyroidism, 18% with hemicastration and 123% with the combination of the two procedures. Numbers of round spermatids showed similar increases: 59% with hypothyroidism, 45% with hemicastration and 95% with the combination of the two procedures. It is concluded that the effects of the combination of transient neonatal hypothyroidism and hemicastration are additive with respect to testicular mass, and numbers of Sertoli and germ cells.
D. R. Simorangkir, D. M. de Kretser, and N. G. Wreford
D R Simorangkir, S Ramaswamy, G R Marshall, R Roslund, and T M Plant
In primates, the time course of Sertoli cell proliferation and differentiation during puberty and its relationship with the expansion of undifferentiated type A spermatogonia that occurs at this critical stage of development are poorly defined. Mid and late juvenile and early and late pubertal male rhesus monkeys were studied. Testes were immersion fixed, embedded in paraffin, and sectioned at 5 μm. Sertoli cell number per testis, S-phase labeling (BrdU), and growth fraction (Ki67 labeling) were determined and correlated with corresponding parameters for undifferentiated type A spermatogonia (A dark and A pale). Dual fluorescence labeling was used in addition to histochemistry to monitor spermatogonial differentiation during the peripubertal period using GFRα-1 and cKIT as markers. While the adult complement of Sertoli cells/testis was attained in early pubertal monkeys after only a few weeks of exposure to the elevated gonadotropin secretion characteristic of this developmental stage, the number of undifferentiated type A spermatogonia several months later in mid pubertal monkeys was only 50% of that in adult testes. Both A dark and A pale spermatogonia exhibited high S-phase BrdU labeling at all stages of juvenile and pubertal development. Spermatogonial differentiation, as reflected histochemically and by relative changes in GFRα-1 and cKIT expression, was not observed until after the initiation of puberty. In the rhesus monkey and maybe in other higher primates including human, the pubertal proliferation of undifferentiated spermatogonia is insidious and proceeds in the wake of a surge in Sertoli cell proliferation following termination of the juvenile stage of development.