Response of Cloudman S91 melanoma cells to melanocytestimulating hormone: enhancement by cytochalasin B.

Cloudmann S 91 mouse melanoma cells treated for 5 days with melanocyte-stimulating hormone (MSH), cytochalasin B (CB), or both, exhibited changes in cell volume, population, nucleation, and pigment production. Cells treated with CB or CB in combination with MSH were eight to nine times larger, rounder, multinucleated, and heavily pigmented. CB alone increased melanin and DNA per nucleus threefold. CB in combination with MSH increased melanin per nucleus 30-fold. Data on DNA per nucleus suggest that CB-treated cells remained in the G phase longer than did control cells. MSH alone caused a reduction in cell population and a fourfold increase in melanin per nucleus.