STIMULATION OF INTESTINAL GROWTH IS ASSOCIATED WITH INCREASED INSULIN-LIKE GROWTH FACTOR-BINDING PROTEIN-5 MESSENGER-RNA IN THE JEJUNAL MUCOSA OF INSULIN-LIKE GROWTH FACTOR-I-TREATED PARENTERALLY FED RATS

Surgically stressed rats maintained with total parenteral nutrition (T PN) exhibit jejunal atrophy, which can be attenuated by insulin-like g rowth factor-I (IGF-I) but not by growth hormone (GH) treatment, in or der to understand the basis for the selective action of IGF-I, the lev els of mRNAs encoding IGF-I, IGF-binding proteins (IGFBPs), IGF-I rece ptor, and GH receptor/binding protein (GHR/GHBP) were determined in ra ts given TPN and treated with GH, IGF-I, or GH + IGF-I. GH treatment s ignificantly stimulated hepatic IGF-I mRNA. IGF-I treatment did not af ter liver IGF-I mRNA, nor was there any evidence for interaction betwe en GH and IGF-I. Jejunal mucose IGF-I mRNA, was extremely low and was not altered by TPN ctp by any of the hormonal treatments, The inabilit y of GH to stimulate jejunal growth was not associated with a deficien cy In GHR/GHBP mRNA, in jejunal mucosa, IGF-I and GH treatment indepen dently and synergistically stimulated IGFBP-3 mRNA. IGF-I stimulated j ejunal IGFBP-5; mRNA, but GH had no effect on IGFBP-5 mRNA, The levels of IGF-I acceptor and IGFBP-1, 2, 4, and 6 mRNAs were extremely Bow a nd/or were not altered by any of the treatments. These results suggest that the ability of exogenous IGF-I, but not GH, to induce IGFBP-5 mR NA in jejuna( mucosa may lead to the selective growth-promoting effect oi IGF-I. Jejunal mucosa IGFBP-3 mRNA levels were not correlated with altered growth, We postulate that IGFBP-5 positively modulates the an abolic effects induced by exogenous IGF-I in the jejunum.