Hormonal Control of Pelage Cycles In The Mink

Abstract

Abstract: Studies on hypophysectomized mink ( Mustela vison ) indicate that the pituitary gland is necessary for normal pelage cycles. Animals hypophysectomized in both the winter and summer coats molted and regrew hair in an asynchronous continuous fashion, but maintained a coat which resembled the winter pelage; at the same time intact controls underwent the normal type and sequence of hair changes. The administration of pregnant mare serum, luteinizing hormone and follicle stimulating hormone to intact mink, and the administration of unfractionated ovine gonadotrophin to intact and hypophysectomized mink in the winter pelage, did not induce molting or the growth of summer pelage after hair growth had been initiated by plucking. Gonadectomy, during the growth or maintenance of the winter pelage, failed to affect the normal seasonal changes from the winter to the summer pelage, nor did the administration of purified thyroid stimulating hormone to hypophysectomized mink in the winter pelage induce molting or the regrowth of summer hair after hair growth had been initiated by plucking. Bilateral adrenalectomy appeared to hasten the spring pelage change in mink while the administration of hydrocortisone to intact mink, prior to and during the spring molt, inhibited the normal hair changes. Purified corticotrophin administered to hypophysectomized mink of the ancestral genotype (an an) in the winter pelage stimulated melanogenesis in plucked hair follicles so that nonagouti hair (summer type) was grown, while uninjected hypophysectomized and intact controls regrew agouti hair (winter type) after hair growth had been similarly induced.