Role of FSH in regulating testicular germ cell transformations in the rat: a study using DNA flow cytometry

Abstract

The role of FSH in regulating testicular germ cell transformations during initiation and maintenance of spermatogenesis in the pubertal and adult rat has been studied using DNA flow cytometry (FCM). The cell types were quantified on the basis of their DNA content using DNA specific fluorochrome DAPI (4,6-diamidino phenylindole). Pubertal (30-d old) and adult (100-d old) rats were deprived of endogenous FSH support for 10 d by daily injection (200 μl d^-1) of a characterized FSH antiserum; the control group received an equivalent volume of normal rat serum. FSH deprivation did not lead to any change in serum testosterone levels. The relative proportion of testicular germ cells in the FSH deprived pubertal rat showed a 90% reduction in 1C (round spermatids) and 260% and 90% increase in 2C (spermatogonia) and 4C (spermatocytes) cells respectively. While the overall conversion of 2C to 1C (1C:2C ratio) was reduced by 98%, the transformation of 2C to 4C (4C: 2C ratio) and 4C to 1C (meiotic division 1C: 4C ratio) was inhibited by 43% and 93% respectively. In the FSH-deprived adult rat the overall conversion of 2C to 1C was reduced by 26% (P < 0.05) only. The 2C and 4C population of cells increased by 47% and 97% respectively (P < 0.025) and the 4C:2C ratio by 47% (P < 0.05). While the meiotic division (1C:4C ratio) was reduced by 54% (P < 0.001), the post-meiotic differentiation of round spermatids to elongate-spermatids (HC:1C) was inhibited by 68% (P < 0.001). A positive correlation (r = 0.95) in per cent HC and a negative correlation (r = -0.67) in per cent 4C cells to the dose of FSH antiserum injected was observed. It is concluded from this that FSH has a role in the onset of meiotic prophase and meiotic division during the first wave of spermatogenesis occuring in the pubertal rat and during adulthood FSH appears to be involved in regulating meiotic division and post-meiotic transformation of spermatids.