Seasonal polymorphism of the adrenal cortex in the male mink.

Adrenal glands of adult and young male mink were examined for a period of twelve months from July, 1970 and the seasonal variations in the relative widths of the cortex and medulla were investigated using histometric procedures. The medulla to cortex ratio in adult mink was noted to be increased during the months immediately following the breeding season although no consistent change was noted in the total size of the adrenal gland. Histochemical analysis using periodic acid Schiff reagent (PAS) for carbohydrates, and Oil red-0-stain for lipids revealed focal accumulations of pigment cells in the zona reticularis during the post breeding season. The presence of strands of PAS positive cells in the outer zones of adrenal cortex just before the peak of the breeding season indicates that these cells may be in the process of migration and infiltration from the zona glomerulosa to the zona reticularis where they become encased by a thin layer of connective tissue. The aggregation of PAS and Oil red-0 positive cells in the zona reticularis, previously assumed to be a response to hormone treatment, may be a normal feature associated with the onset of testicular quiescence in sexually mature mink.