Immunohistochemical and ultrastructural age-related changes in rat lactotroph cells

Ageing produces alterations in some functions of the hypothalamo-pituitary axis leading to sexually dimorphic changes in the prolactin (PRL)-secreting cells. Since quantitative morphological data of these age-associated alter ations are scarce, we carried out a morphometric immunohistochemical assess ment as well as an ultrastructural study of the PRL, cell population in mal e and female rats of different ages. Young (3-month-old), old (20-month-old ), and senescent (31-month-old) Sprague-Dawley rats of both sexes were sacr ificed by rapid decapitation, their pituitaries immediately dissected out a nd processed for both immunohistochemistry and electron microscopy. Analysi s of different morphometric parameters revealed that the cell density (CD) and volume density (VD) significantly decreased with age in male rats. In f emales, while CD showed a significant age-related diminution when young rat s were compared to old ones, this parameter increased in senescent animals. The VD presented higher values in senescent rats. When the data were compa red between sexes, VD was found to be higher in females if old and senescen t rats were considered. Finally, CD increased significantly in females when compared to males. The ultrastructure of the PRL cells from old and senesc ent animals of both sexes exhibited changes suggestive of an hyperstimulati on state, with some prolactotrophs having the appearance of cells undergoin g an involutive process. We conclude that ageing has a differential impact on the PRL. cells of male and female rats with respect to the immunohistoch emical and ultrastructural features of that cell population.