Changes in the proportion of cells within various
DNA classes of dispersed testicular cells from the developing rat were monitored by microflow fluorometry and correlated with changes in the function of the pituitary (FSH), of the Leydig cells (
androgens) and Sertoli cells (
androgen-
binding proteins, ABP). Peaks of
androgens and of FSH appeared simultaneously and coincided with an accumulation of
tetraploid cells and with the first appearance of haploid cells in the testis and ABP in the epididymis.
Estrogen treatment (5 micrograms/day) of developing rats from day 7 completely prevented the appearance of haploid cells in the testis as well as ABP in the epididymis. In these animals the wave of
tetraploid cells started and progressed normally, indicating that transformation and progression of germinal cells to the stage of the primary spermatocytes were taking place. A combined treatment with FSH and
dihydrotestosterone propionate (DHTP) resulted in a premature start of Sertoli cell secretion of ABP into the epididymis, but in a normal appearance of haploid and
tetraploid cells. The time correlation between peaks in FSH/
androgens, the start of Sertoli cell secretion, and the occurrence of haploid cells in the testis stresses the importance of these two
hormones for normal Sertoli cell function and the importance of a functional Sertoli cell for the completion of meiosis.