Synthesis and biological activity of .beta.-melanotropins and analogs

Abstract
Synthetic [Arg8]-, [Gly10]- and [Phe12]-.beta.c1-MSH and .beta.p-MSH were prepared by the solid-phase method. Their lipolytic and melanotropic activities were compared to each other and with those of previously synthesized .beta.c1-MSH, [formyl-Trp12]-.beta.c1-MSH, and .beta.b-MSH. Replacement of Gln8 of .beta.c1-MSH by Arg causes a greater decrease in melanotropic activity than in lipolytic activity. When Phe10 of .beta.c1-MSH is replaced by Gly, both activities are destroyed. Alteration or replacement of Trp12 of .beta.c1-MSH by formyl-Trp or Phe has little effect on the melanotropic activity while the lipolytic activity is greatly decreased. Replacement of Ser2 of .beta.b-MSH by Glu induces a 3-fold increase in [frog skin] melanotropic activity but it does not affect the lipolytic activity.