Hypothalamic input is required for development of normal numbers of thyrotrophs and gonadotrophs, but not other anterior pituitary cells in late gestation sheep

To evaluate the hypothalamic contribution to the development of anterior pituitary (AP) cells we surgically disconnected the hypothalamus from the pituitary (HPD) in foetal sheep and collected pituitaries 31 days (d) later. Pituitaries (n=6/group) were obtained from foetal sheep (term = 147 +/- 3 d) at 110 d (un-operated group) of gestation and at 141 d from animals that had undergone HPD or sham surgery at 110 d. Cells were identified by labeling pituitary sections with antisera against the six AP hormones. Additionally, we investigated the co-localization of glycoprotein hormones. The proportions of somatotrophs and corticotrophs were unchanged by age or HPD. Lactotrophs increased 80 over time, but the proportion was unaffected by HPD. Thyrotrophs, which were unaffected by age, increased 70 following HPD. Gonadotrophs increased with gestational age (LH+ cells 55 ; FSH+ cells 19-fold), but this was severely attenuated by HPD. We investigated the possible existence of a reciprocal effect of HPD on multipotential glycoprotein-expressing cells. Co-expression of LH-TSH was extremely rare (