Serum prolactin and dehydroepiandrosterone concentrations during the summer and winter hair growth cycles of mink (Mustela vison)

We investigated the relationship between serum concentrations of prolactin (PRL) and dehydroepiandrosterone (DHEA) during initiation and development o f summer and winter hair growth (anagen) cycles in mink. In the spring, hal operidol (HAL) increased PRL concentrations and induced summer anagen earli er than controls, whereas melatonin (MEL) inhibited PRL secretion and compl etely blocked summer anagen. In the fall, HAL increased PRL concentrations, inducing anagen at an earlier time than controls, although the resulting f ur was abnormal being almost devoid of underhair fibers. Exogenous MEL duri ng the fall reduced PRL concentrations, initiating winter anagen 4 weeks ea rlier than controls. Adrenalectomy (ADX) induced earlier onset of summer an d winter anagen and neutralized the inhibitory effects of HAL in the fall a nd MEL in the spring. No change in serum DHEA concentrations was observed d uring the onset of summer or winter anagen in any group although MEL increa sed DHEA levels from 27 March through 5 June relative to HAL-treated mink. We conclude that changes in serum levels of DHEA and PRL are not requisite to onset of summer or winter anagen in mink. It is possible that metabolite s of DHEA and/or PRL may still affect other aspects of the hair growth cycl e. (C) 1998 Elsevier Science Inc. All rights reserved.