GH ELEVATES SERUM IGF-I LEVELS BUT DOES NOT ALTER MUCOSAL ATROPHY IN PARENTERALLY FED RATS

Growth hormone (GH) action is primarily mediated by insulin-like growt h factor I (IGF-I), although both growth factors show tissue-selective effects. We investigated the effects of GH, IGF-I, and GH plus IGF-I on jejunal grow th and function in rats maintained with total parenter al nutrition (TPN) and given recombinant human GH (rhGH) (400 mu g/day sc, twice daily) and/or rhIGF-I (800 mu g/day in TPN solution) for 5 days. Administration of GH or IGF-I alone produced similar increases i n serum IGF-I levels and body weight; GH plus IGF-I further increased these parameters. TPN reduced mucosal mass, protein and DNA content, v illus height, crypt depth, and enterocyte migration rate. IGF-I or GH plus IGF-I produced equivalent increases in all intestinal growth para meters; GH alone had no effect. GH, IGF-I, or GH plus IGF-I reduced TP N-induced increases in sucrase-specific activity. IGF-I, but not GH, a ttenuated TPN-induced increases in tissue conductance and carbachol-st imulated ion secretion. In contrast to IGF-I, GH does not stimulate in testinal growth during TPN and has less effect on normalizing TPN-indu ced changes in epithelial function.