An immunocytochemical study of effects of light deprivation on prolactin cells in the adenohypophysis of the golden hamster

Abstract

Population ratio and morphology of prolactin cells were studied by employing immunohistochemical methods in the adenohypophysis of normal and experimental golden hamsters of both sexes at 16 weeks of age. Prolactin cells occupied 29% of the total adenohypophyseal cells in the intact males exposed to 141 10 h lightldark schedule. After stimulation of the pineal activity by blinding or exposure of males to continuous darkness for eight weeks, prolactin cells became atrophic and were reduced in population to 17% and 13%, respectively. ~i n e a l e c t om~~r e v e ntot e sdo me extent the effects of the above treatments; thus, prolactin cells constituted 27% in the pinealectomized and blinded hamsters, and 19% in the pinealectomized and darknesstreated group; and their morphology was comparable with that of the intact controls. Prolactin cells in the normal females were apparently larger in size and more numerous as compared with those of the normal males, comprising 47% of cell population in the anterior pituitary. In response to light deprivation, prolactin cells were atrophic with a diminished cytoplasm and decreased in cell number as reflected in the population ratio of 27% in the blinded and 21% in the darknesstreated groups. In pinealectomized females combined with blinding or darkness-treatment, prolactin cells contained an abundance of secretory granules in the cytoplasm and maintained the population ratio comparable to that in the intact females. The present study revealed that light deprivation exerts an inhibitory effect on the secretory activity of prolactin cells and also causes hypoplasia of prolactin cells in the hamster adenohypophysis, the effects being mediated by the pineal gland.