Physiological doses of prolactin stimulate pelage pigmentation in Djungarian hamster.
The Djungarian hamster exhibits a dark agouti pelage during the summer. Under the influence of decreased daylength, this species molts and develops a predominantly white winter coat. After a patch of white fur was plucked from hamsters housed in short photoperiod, chronic infusion of 10 or 20 micrograms ovine prolactin (o-PRL)/day led to the growth of a patch of pigmented fur, thus reversing the effect of the decreased daylength. Circulating o-PRL levels produced by the 10-micrograms/day infusions ranged from 17.9 +/- 4.0 to 35.1 +/- 13.8 (SE) ng/ml and thus approximated the endogenous circulating prolactin levels found in hamsters with the dark summer pelage (6, 9). Infusion of o-PRL stimulated pigmentation of the pelage of castrated as well as intact hamsters, suggesting that the testes do not mediate this effect. Infusion of ovine growth hormone (20 micrograms/day) did not stimulate pigmentation, and infusion of alpha-melanocyte-stimulating hormone (10 micrograms/day) gave inconclusive results.
D000818:Animals; D006224:Cricetinae; D003692:Delayed-Action Preparations; D013006:Growth Hormone / Q000494:pharmacology; D007279:Injections, Subcutaneous; D009074:Melanocyte-Stimulating Hormones / Q000494:pharmacology; D010858:Pigmentation / Q000187:drug effects; D011388:Prolactin / Q000008:administration & dosage / Q000502:physiology*; D012756:Sheep; D013739:Testosterone / Q000502:physiology
D003692:Delayed-Action Preparations; D013739:Testosterone; D011388:Prolactin; D013006:Growth Hormone; D009074:Melanocyte-Stimulating Hormones