Gonadotrophic Control of Tritiated Thymidine Incorporation in the Germinal Cells of the Rat Testis

Abstract

The gonadotrophic control of spermatogenesis varies with age. Thus, ovine fsh stimulates spermatogenesis in the hypophysectomized prepubertal rat more effectively than ovine lh whereas the opposite is found in the adult (Ortavant, Courot & de Reviers, 1969;Courot, Ortavant & de Reviers, 1971). Gonadotrophic hormones reduce the proportion of germinal cells which undergo degeneration. It was thought probable that this effect was the result of actions of these hormones on the metabolism of germinal cells. We have started to investigate this problem by studying the effects of fsh and lh on the synthesis of DNA by spermatogonia and primary spermatocytes in the rat. It has previously been shown that hypophysectomy reduces the intensity of [3H]thymidine-labelling of the DNA in these cells (R. Ortavant, unpublished data).Six prepubertal and six adult Wistar rats were hypophysectomized and then treated subcutaneously with highly purified ovine fsh or lh: the adult rats received three injections, each containing 100 µg fsh-cnrs-de 58 (xl-5 nih fsh-s1) or 100^g lh-gnrs-m2 (x 1-4 nih lh-s1), at 12-hourly intervals starting 30 days after hypophysectomy; the prepubertal rats received 15^g fsh-cnrs-m1 ( x4 nih fsh-s1) or 20 µg lh cnrs-m1 ( 1-5 nih lh-s1) twice daily for 12 days, starting immediately after hypophysectomy on the 27th day after birth. Previous experiments using these treatment schedules had demonstrated an effect of fsh on spermatogenesis in prepubertal rats and of lh in adults. All the rats were killed 12 hr after the last injection of hormone, 1 hr after intraperitoneal administration of [3H]thymidine (IT /iCi/g body weight, specific activity: 10 Ci/mmol).The testes were fixed in Bouin-Hollande solution and autoradiographs of 5-µ paraffin-wax sections were prepared with Ilford K5 emulsion. Photo¬ metric grain density measurements were made over type A3 and A4 spermatogonia (Clermont & Bustos-Obregon, 1968) at stages 3 and 4 of the cycle of the seminiferous epithelium and over preleptotene and leptotene primary spermatocytes at stages 8 and 1 (Roosen-Runge & Giesel, 1950). The grain density was measured over sixty nuclei of each type of cell in each animal and the median intensities of labelling were compared by the method of Lazar & Gerard-Marchant (1965) after subtraction of the background level. 451

Autoradiographic Study of Lysine and Arginine Incorporation Stimulated by Follicle-Stimulating Hormone in the Mouse Testis in Vivo

“…At preleptotene the DNA content of the cell increases from the diploid to the tetraploid amount (Courot, Hochereau-de Reviers & Ortavant, 1970). Ortavant, Courot & Hochereau-de Reviers (1972) found that administration of gonadotrophins to hypo¬ physectomized rats increases the uptake of thymidine in preleptotene spermatocytes as well as in type A3 and A4 spermatogonia, and they suggested that this was due to an increase in the proportion of cells doubling their content of DNA. As in the spermatogonia, it is likely that the stimulatory effect of FSH on incorporation of lysine and arginine in preleptotene spermatocytes was due to an increase in the mean amount of histone being synthesized at the same time as DNA.…”