Sexually dimorphic effects of aging on rat somatotropes and lactotropes

During the aging process modified functions of hypothalamic factors may cause sexually dimorphic changes in pituitary somatotropes and lactotropes. To test this hypothesis, pituitary tissue from young adult (4 months) and old (20-22 months) male and female rats was labeled immunocytochemically for growth hormone (GH) and prolactin (PRL). The total amount of immunoreactive material as well as the total area and number of immunoreactive structures were evaluated. With increasing age the intracellular GH content was moderately increased in male and decreased in female rats. An age-dependent PRL increase, due both to increased cell number and intracellular hormone content, was present only in female rats. The amount of GH- and PRL-immunoreactive material, distributed into classes of increasing density, differed both between sex and age groups. Our results indicate that the aging process of the somatotrope and lactotrope cell populations in rats appears to be different in the two sexes.