Histologic identification and immunochemical studies of prolactin and growth hormone in the primate pituitary gland

The two acidophilic cell types were tinctorially differentiated in rhesus monkey pituitaries as well as in pituitaries of other species of monkeys and apes and were identified by immunofluorescence as the prolactin and the growth hormone (GH) cells. The number of prolactin cells was significantly greater in adult than in juvenile rhesus monkeys. During late pregnancy and lactation, these cells appeared to occupy 60-80% of the entire anterior lobe of the rhesus monkey. The concentration of prolactin and CH was measured by radioimmunoassay in pituitary extracts (PE) from pools of juvenile male, juvenile female, adult male and adult female rhesus monkey pituitaries. More prolactin was present in PEs from adult than from juvenile animals, with the highest concentration being present in adult females. A similar relationship was observed with GH. The qualitative immunologic relationship between ovine prolactin and prolactin in the rhesus monkey PEs, and between human GH and GH in the PEs, was established using agar gel diffusion. The two prolactin hormones were partially related immunochemically, while the two GHs were shown to be immunochemically identical. In intact juvenile female rhesus monkeys given estradiol benzoate, the concentrations of pituitary and serum prolactin were elevated over that of the controls, while the concentration of pituitary GH was decreased. An increase in the number of prolactin cells was also observed in the steroid-treated animals. These observations demonstrate further that prolactin and GH reside in separate cells in the primate pituitary and that the concentration of these two hormones varies depending upon age, sex, or stage of the reproductive cycle of the animal.