In humans and macaques, the ontogeny of Sertoli cell proliferation is different from that in rodents (54-60). Cortes et al. (56), using autopsy material from boys and men who had died in traumatic accidents, described two phases of Sertoli cell proliferation, one immediately after birth and one later at puberty. Each of these periods in higher primates is associated with elevated levels of gonadotropins (61). In the rhesus monkey, the number of Sertoli cells per testis was increased fivefold from infancy to the juvenile phase of development, with a further sixfold increase from the juvenile to the adult phase. These increments in Sertoli cell number occurred during infancy and the puber-tal period concomitant with the elevated gonadotropin levels that are characteristic of these developmental phases (57). Moreover, GnRH administration to juvenile rhesus macaques that are naturally hypogonadotropic resulted in precocious LH and FSH secretion that, in turn, stimulated a premature increase in the number of Sertoli cells (57). Finally, administration of synthetic human LH and FSH, either alone or in combination, to juvenile rhesus monkeys for 11 d resulted in an increase in the number of Sertoli cells (59). Moreover, in contrast to the case in rodents, LH and FSH were equally effective in stimulating proliferation of Sertoli cells. The cellular and molecular actions of the two gonadotropins, LH and FSH, therefore, require further elucidation.
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