Bilateral adrenalectomy induces early onset of summer fur growth in mink (Mustela vison).

The purpose of this study was to determine the effects of bilateral adrenalectomy on the time at which growth of the summer pelage begins in mink. Bilateral adrenalectomy of adult female mink between 2 and 11 March 1991, supplemented with deoxycorticosterone (DOC) as a mineralocorticoid, resulted in the onset of the summer fur growth approximately 5 weeks earlier than the controls (P < 0.01). Mink with their adrenal glands intact and treated with DOC, exhibited summer fur growth 2 weeks earlier than the controls (P < 0.01). The duration of time between the first observed hair growth and attainment of maximal guard hair length, was approximately 10 days longer in mink with their adrenal glands intact and supplemented with DOC than the controls (P < 0.05). Adrenalectomized mink treated with DOC exhibited guard hair growth for approximately 13 days longer than controls (P < 0.05). Although exogenous DOC initiated hair growth, the rate of growth appeared to be reduced. These data suggest that adrenal hormones, of undetermined identity, exert a tonic inhibitory effect on the initiation of summer fur growth in mink and may be part of the mechanism through which changes in photoperiod regulate the onset of hair growth cycles.