SEXUALLY DIMORPHIC EFFECTS OF AGING ON RAT SOMATOTROPH CELLS - AN IMMUNOHISTOCHEMICAL AND ULTRASTRUCTURAL-STUDY

Aging produces alterations in certain functions of the hypothalamo-pit uitary axis that result in sexually dimorphic changes in the somatotro phs. Since quantitative morphological data on these age-associated alt erations are scarce, we prompted to make a morphometric immunohistoche mical assessment as well as undertake an ultrastructural study of the somatotrophic (GH) cell population in male and female rats of differen t ages. Young (3-month-old), old (20-month-old), and senescent (29-mon th-old) Sprague-Dawley rats of both sexes were sacrificed by rapid dec apitation, their pituitaries immediately dissected out, and processed for both immunohistochemistry and electron microscopy. Analysis of dif ferent morphometric parameters revealed that surface density, volume d ensity, and cell density significantly decreased in old and senescent rats as compared to young animals, with this reduction being clearly m ore marked in females. Both the GH-cell area and perimeter decreased i n senescent male rats, while these parameters increased in senescent f emales. The ultrastructure of the GH cells from old and senescent anim als of both sexes evinced changes suggestive of an immature state, wit h some somatotrophs having the appearance of cells undergoing an invol utive process. We conclude that aging has a differential impact on the GH cells of male and female rats with respect to the immunohistochemi cal and ultrastructural features of that cell population.