FUNCTIONAL ACTIVE RECEPTORS FOR INSULIN-LIKE GROWTH-FACTOR-I (IGF-I) AND IGF-II ON INSULIN-PRODUCING, GLUCAGON-PRODUCING, AND SOMATOSTATIN-PRODUCING CELLS

Insulin-like growth factors I and II (IGF-I and IGF-II) are expressed at high levels in the endocrine pancreas during development and tissue regeneration. However, their effects at the endocrine pancreas are po orly understood. We searched for receptors of IGF-I and IGF-II and pos sible biological effects on clonal insulin-secreting (HIT), glucagon-s ecreting (INR1G9), and somatostatin-secreting (RIN 1027 B2) cell lines . Our data showed that HIT cells and RIN 1027 B2 cells express specifi c type I and type II IGF receptors. INR1G9 cells possess type II IGF r eceptors and IGF-I binding sites with the same affinity for both IGF-I and IGF-II. In HIT cells, insulin secretion was not influenced by eit her peptide. Proinsulin gene transcription was stimulated by IGF-II bu t not by IGF-I. IGF-I potently inhibited proglucagon gene transcriptio n and glucagon secretion in INR1G9 cells, whereas IGF-II only inhibite d glucagon release. In RIN 1027 B2 cells, IGF-I but not IGF-II increas ed somatostatin output, whereas both stimulated somatostatin gene expr ession. These data demonstrate the presence of classic type I and type II IGF receptors on insulin-, glucagon-, and somatostatin-secreting c ells. Both peptides may be important regulators of endocrine pancreati c function in terms of islet hormone release and gene expression. Ther efore, both peptides may be involved in the regulation of intraislet c ellular homeostasis. Copyright (C) 1996 by W.B. Saunders Company.