Chemically synthesized bovine growth hormone (bGH) bGH 96-133 and its human homologue, hGH 95-133, have similar in vitro biological activities. Unlike native GH, bGH 96-133 and hGH 95-133 were completely without adipogenic or anti-insulin activity at doses up to 10 microM. bGH 96-133 had insulin-like activity, with a 100% increase in glucose uptake at 10 microM. bGH was anti-mitogenic and bGH 96-133 and hGH 95-133 were mitogenic (EC50 approximately 180 nM and maximal response at 1-2 microM). Only bGH 96-133 and hGH 95-133 displaced [125I]hGH 95-133 binding from 3T3-F442A fibroblasts with a Kd between 60-120 nM. bGH, hGH, insulin and IGF-I were without effect on [125I]hGH 95-133 binding. bGH 96-133 and hGH 95-133 did not significantly inhibit [125I]hGH or [125I]IGF-I binding. These experiments indicate that GH containing peptides bGH 96-133 and hGH 95-133 have mitogenic and insulin-like activity without the adipogenic, anti-insulin or anti-mitogenic activity of bGH. These peptides have a specific binding site which appears to be distinct from the GH, insulin and IGF-I receptors.