A peptide that inhibits the mitogenic stimulation of Swiss 3T3 cells by bombesin or vasopressin.

The synthetic peptide [D-Arg1,D-Pro2,D-Trp7,9,Leu1]substance P inhibits the stimulation of DNA synthesis induced in Swiss 3T3 cells by bombesin or vasopressin, but not that induced by a wide range of other growth factors and mitogens. The stimulation induced by 10 pM-3 nM-bombesin is inhibited by 1-30 microM-antagonist in a manner consistent with competition at the bombesin receptor. The inhibition by the antagonist of the stimulation induced by vasopressin suggests a previously unrecognized interaction of the antagonist with vasopressin receptors. The antagonist should be useful in studies of cell proliferation both in vivo and in vitro.