No abstract

Summary. Sertoli

Changes in testicular androgen receptor numbers were studied in lambs from 25 to 100 days of age. During this period, cytoplasmic receptors increased from 5 to 80 pmol/testis and nuclear receptors from 1 to 12 pmol/testis, while the total volume of Leydig cells increased 7-fold. The total number of Sertoli cells doubled between 25 and 40 days of age. From 40 days onward their number remained constant while their cellular and nuclear sizes increased by a factor of 3 and 1.5 respectively. Cytoplasmic receptor concentration was positively correlated with the number of Sertoli cells per section of seminiferous tubule, and negatively correlated with the number of germinal cells per cross section. One explanation for these results could be that Sertoli cells are the main androgen target cells in lamb seminiferous tubules.

3) The season of birth influenced the Sertoli cell stock formation in the ram. Daylength modified testicular development in the cockerel and the sheep. 4) Between-strain differences were more marked for the testis than for body growth in the cockerel. In the ram, Sertoli cell stocks were similar between half-brothers but significantly different between sires.Introduction.

Abstract. Male rats treated prenatally with busulfan in order to render them aspermatogenic were treated between 23 and 38 days of age either with testosterone, or flutamide. In such aspermatogenic rats, testosterone supplementation stimulated the growth of accessory sex organs, markedly decreased the secretion of gonadotrophins (by 61% for LH and 83% for FSH), decreased testicular weight (–60%) as well as all parameters relating to testicular histology. Flutamide treatment decreased the weight of accessory sex organs, stimulated the secretion of both LH (+200%) and FSH (+63%) by inhibition of the negative feedback of testosterone; endogenous testosterone secretion was increased by 363%. Testicular weight was increased by 44% and the total volume and the cytoplasmic and nuclear area of Leydig cells were increased by 254 and 28%, respectively, but their number per testis was unchanged. The number of Sertoli cells per testis was increased by 49%, but their nuclear area was not modified. In aspermatogenic prepubertal rats, the large increase in plasma FSH demonstrated that FSH release was partly under the control of inhibin, secreted by Sertoli cells when germinal cells were present. Nevertheless, FSH levels after testosterone (inhibition) or flutamide treatment (stimulation) clearly demonstrated that, in the growing rat, FSH secretion is also partly dependent on the negative feedback of testosterone. In the absence of germ cells, FSH was able to re-initiate Sertoli cells mitoses, but not their functional activity. LH secretion was solely controlled by the negative feedback of androgens and, even in the absence of germinal cells, Leydig cells were able to respond to LH stimulation by an increase in testosterone secretion.