THE EFFECTS OF THE PINEAL GLAND ON PROLACTIN IN THE BLIND-ANOSMIC RAT

Abstract

The morphological and physiological effects of pineal gland activity on the prolactin-secreting cells of the anterior pituitary were examined in blind-anosmic male and female rats. Prolactin synthesis was measured by the ability of anterior pituitaries to incorporate ³H-leucine into prolactin in vitro. Pituitary storage of prolactin was assessed by measuring radioimmunoassayable prolactin levels in the pituitaries in vivo and the total amount of immunoassayable prolactin in vitro. The effects of the activated pineal on prolactin release were estimated by monitoring radioimmunoassayable serum prolactin levels. Finally, the morphology of the prolactin cells was analyzed by both light microscopic immunocytochemistry and transmission electron microscopy. Eight weeks after blinding and olfactory bulbectomy in prepubertal male and female rats, prolactin synthesis, storage and release were all significantly decreased compared to unoperated control values. Pinealectomy in blind-anosmic rats completely prevented these effects. Similar results were obtained four weeks after treatment, but not after only one week. Furthermore, the reductions in prolactin synthesis, storage and release were not a consequence of the pineal-induced gonadal atrophy in these animals, since these effects persisted in ovariectomized-blind-anosimic rats. The pineal also elicited these effects in female rats rendered blind-anosmic after puberty, though to a lesser degree than when immature animals were used. Concomitant with these alterations in prolactin synthesis, storage and release were regressive changes in the morphology of individual prolactin cells and in the number of these cells in the pituitary. Anterior pituitaries from blind-anosmic rats were approximately half the weight of glands from intact animals and contained a third less DNA. This loss of cell number was largely accounted for by a reduction in the number of prolactin cells, as shown by immunocytochemistry. Additionally, each prolactin cell was smaller in size in blind-anosmic female rats and showed scant endoplasmic reticulum, a small Golgi complex, few secretory granules and rare exocytosis patterns. From these data I conclude that the pineal gland exerts a strong inhibition on the prolactin cells of blind-anosmic rats.