Castration Effects on the Gonadotrope Cell Populations of the Fetal Sheep Pituitary in Late Gestation

Abstract

This immunocytochemical study focused on the role of fetal gonads in the regulation of gonadotrope cell populations in the fetal sheep pituitary in late gestation. Male and female sheep fetuses were castrated at 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 populations (i.e. the number of gonadotrope cells vs. the total number of the pituitary cell counted) and the mean cell area were determined. Castration 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 females (46.4 ± 0.6 vs. 51.6 ± 0.4 µm², p < 0.01, in males and 43.0 ± 0.5 vs. 50.0 ± 1.1 µm², p < 0.01 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 < 0.01, in males and 2.3 ± 0.1 vs. 1.1 ± 0.3, p < 0.02, in females). Moreover, castrated males had higher FSH cell percentages than castrated females (p < 0.02). The individual FSH cell area was smaller in castrated fetuses than that in controls (44.7 ± 1.4 vs. 51.2 ± 1.4 µm², p < 0.05, in males and 42.1 ± 0.8 vs. 51.6 ± 0.8 µm², p < 0.01, in females). The LH-FSH cell percentage was slightly higher in castrated 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 the fetal sheep pituitary previously observed in late gestation.

Targeted disruption of the pituitary glycoprotein hormone alpha-subunit produces hypogonadal and hypothyroid mice.

“…However, gonadotropes in -/-pituitaries did not exhibit a significant increase in size or number, consistent with the minimal effects on gonadotropes in rats or sheep gonadectomized in utero (Nakai et al 1972;Messaoud-Toumi et al 1993). Steroid hormone feedback on LH and FSH transcription does take place in immature animals, as increases in LH and FSH mRNA levels have been observed in male rats gonadectomized as young as 10 days after birth (Pakarinen and Huhtaniemi 1992).…”