GH administration and renal IGF-I system in arthritic rats

Experimental arthritis in rats results in a growth failure and a decrease in circulating and hepatic concentrations of insulin-like growth factor I (IGF-I). Renal damage has also been reported in arthritic rats. The aim of this study was 1) to analyse if alterations in the IGF-I system in the kidney occurs in adjuvant-induced arthritis and 2) to analyse if recombinant human GH (rhGH) administration is able to reverse these effects. Male Wistar rats were injected with complete Freund's adjuvant or vehicle and 22 days later they were killed. Arthritis increased serum creatinine levels, relative kidney weight and IGF-I concentrations in this organ. In a second experiment, arthritic and control rats received rhGH (3 UI/Kg sc) or 250 microl saline from day 14, after adjuvant or vehicle injection, until day 22. IGF-I concentrations were higher in both the renal cortex and medulla of arthritic rats. In contrast, kidney IGF-I mRNA was lower in both areas of arthritic animals. GH treatment significantly decreased serum creatinine levels and IGF-I concentrations in the kidney cortex and medulla of arthritic rats. However, the administration of rhGH to arthritic animals significantly increased the IGF-I gene expression in both the renal cortex and medulla. Serum and kidney concentrations of IGF-I binding proteins (IGFBPs) were increased in arthritic animals and they were reduced by GH administration.

These data suggest that experimental arthritis causes renal dysfunction and GH treatment can ameliorate this effect.