Cytology of the anterior pituitary at different times of the year in normal and methallibure-treated male Columbian black-tailed deer (Odocoileus hemionus columbianus)

Abstract

The application of histochemical staining techniques to the anterior pituitary revealed the presence of seven cell types. Most cell types underwent cyclic changes that could be related to a seasonal pattern of functional activity. The cell type tentatively identified as the interstitial-cell-stimulating hormone (ICSH) (luteinizing hormone) cell had the most pronounced seasonal cycle. Hormonal release by these cells, and other cells tentatively identified as follicle-stimulating hormone (FSH) cells, was judged to be greatest in the fall, but some activity was also apparent during the spring and summer. The somatotrophs appeared most active in spring and summer, whereas the lactotrophs appeared most active in the fall. With the possible exception of the corticotrophs, all the cells of the anterior pituitary showed the least signs of activity in late winter.The pituitaries of methallibure-treated deer sacrificed in July, November, and December contained ICSH cells and FSH cells that were small and chromophobic, whereas other cell types appeared to be affected little or not at all. This suggests that the main effect of methallibure on the anterior pituitary was to suppress the secretory activity of the gonadotrophic cells. The significance of these findings in relation to the hormonal regulation of reproduction and the antler cycle is discussed.