The dual effect of melanocyte-stimulating hormone (MSH) on the growth of cultured mouse melanoma cells

Abstract

Melanotropin (melanocyte-stimulating hormone, MSH) can either stimulate or inhibit the rate of proliferation of melanocytes. Stimulation was observed in cultures of mouse melanoma cells that had low tyrosinase activity and in cells that had normal tyrosinase activity but were grown in medium that was changed frequently or was deficient in tyrosine. In contrast, inhibition of growth was associated with high tyrosinase activity and the presence of tyrosine in the culture medium. Small amounts of exogenous adenosine 3′,5′-cyclic monophosphate (cAMP) stimulate the growth rate of these cells [1]. Since MSH causes an increase in intracellular levels of cAMP 2., 3., 4., it is likely that the stimulation of growth is due to the ability of this hormone to increase the intracellular levels of cAMP. Inhibition of growth in turn is related to the activation of tyrosinase by MSH and the accumulation of toxic substances produced by the tyrosinase reaction.