Growth hormone induces resistance to the mitogenic action of insulin through local IGF-I. Studies in normal and Pygmy T-cell lines.

Growth hormone (GH) and insulin have both mitogenic and metabolic actions. The growth-promoting effects of GH in vivo are thought to be mediated by insulin-like growth factor-I (IGF-I), whereas the metabolic effects of GH are thought to be either direct or mediated by factors other than IGF-I. In previous studies using HTLV-II-transformed T-lymphoblast cell lines established from normal individuals, we have shown that GH preincubation induces resistance to the growth-promoting (mitogenic) action of insulin. In this study, using T-cell lines from 3 American control subjects, 1 African control subject, and 1 African Pygmy (the latter previously shown to be resistant to the growth-promoting actions of both IGF-I and GH), we examined the role of local IGF-I in the mediation of GH-induced resistance to the mitogenic action of insulin. In these studies, we quantified the stimulation of T-cell colony formation in response to insulin in the presence and absence of either GH or IGF-I.(ABSTRACT TRUNCATED AT 250 WORDS)