Cytochalasin B: effects on microfilaments and movement of melanin granules within melanocytes.

The intracellular translocation of melanin granules within both epidermal and dermal melanocytes of Rana pipiens is influenced by cytochalasin B. Cytochalasin B prevents dispersion of pigment granules by melanocytestimulating hormone (MSH) and causes centripetal movement of pigment granules that have been dispersed by MSH. Microfilaments are abundant in the dendritic processes of epidermal melanocytes in which pigment granules have been dispersed by MSH. Microfilaments are dramatically reduced in number in the processes of melanocytes that have been lightened by cytochalasin B. These observations suggest that microfilaments mediate dispersion of pigment granules.