Differential responsiveness of dermal and epidermal melanocytes of Rana pipiens to hormones.

There are 2 populations of melanin-containing pigment effector cells in frog skin–one located in the epideimis, the other in the dermis. Both types of melanocytes exhibit rapid dispersal of pigment granules in the presence of small amounts of MSH. Rapid aggregation of pigment granules occurs when MSH is washed from the skin. Epidermal melanocytes in frog skin that has been treated with MSH do not contract in the presence of melatonin, acetylcholine, or norepinephrine. Dermal melanocytes contract rapidly in the presence of these 3 hormones. The similarity in morphology between epidermal melanocytes of frogs and mammals is striking. (Endocrinology 78: 367, 1966)