CASTRATION EFFECTS ON THE GONADOTROPE CELL-POPULATIONS OF THE FETAL SHEEP PITUITARY IN LATE-GESTATION

This immunocytochemical study focused on the role of fetal gonads in t he regulation of gonadotrope cell populations in the fetal sheep pitui tary in late gestation. Male and female sheep fetuses were castrated a t 112-115 days of gestation and maintained in utero until 139-140 days gestation when their pituitaries were collected. Intact twins served as controls. The percentages of the different gonadotrope cell populat ions (i.e. the number of gonadotrope cells vs. the total number of the pituitary cell counted) and the mean cell area were determined. Castr ation did not affect the LH cell percentage in either sex but resulted in a decrease in the individual LH cell areas of both males and femal es (46.4 +/- 0.6 vs. 51.6 +/- 0.4 mum2, p < 0.0 1, in males and 43.0 /- 0.5 vs. 50.0 +/- 1.1 mum2, p < 0.0 1, in females). By contrast, the FSH cell percentage was increased about twofold in castrated fetuses when compared to intact animals (3.5 +/- 0.3 vs. 1.6 +/- 0.3, p < 0.0 1, in males and 2.3 +/- 0.1 vs. 1.1 +/- 0.3, p < 0.02, in females). Mo reover, castrated males had higher FSH cell percentages than castrated females (p < 0.02). The individual FSH cell area was smaller in castr ated fetuses than that in controls (44.7 +/- 1.4 vs. 51.2 +/- 1.4 mum2 , p < 0.05, in males and 42.1 +/- 0.8 vs. 51.6 +/- 0.8 mum2, p < 0.01, in females). The LH-FSH cell percentage was slightly higher in castra ted males than in control males (0.9 +/- 0.01 vs. 0.8 +/- 0.06, p < 0. 05) and twofold lower in castrated females than in intact females (0.5 +/- 0.05 vs. 0.9 +/- 0.03, p < 0.01). These results suggest that the fetal ovary as well as the fetal testis are involved in the variations of the percentages of the different gonadotrope cell populations of t he fetal sheep pituitary previously observed in late gestation.