Effects of grwoth hormone therapy and malnutrition on the growth of rats with renal failure

We examined the effects of methionylhuman growth hormone (met-hGH) and malnutrition on the growth of 5/6 nephrectomized rats and sham-operated controls. One group of shamoperated rats (PFS) was pair-fed with a group of nephrectomized rats in renal failure (RF); another group of sham-operated rats was fed ad libitum (ALS), and a final group of rats with renal failure (RF-GH) was treated with 4 IU/day met-hGH. After 4 weeks, RF-GH rats gained 12.3±1.7 cm in length; this was more than the 10.2±1.2 cm gain of RF rats (P<0.05). Ingested food was converted into weight gain more efficiently by RF-GH rats than RF rats (267±26 vs 235±38 mg weight gain/g food intake, P<0.05). RF-GH rats also gained more weight (122±25 g) than RF rats (98±27 g), but this difference was not significant (0.05<P<0.1). Insulin-like growth factor (IGF)-I, glucose and insulin levels were not different between RF and RF-GH rats. Food intake of RF and PFS rats was 64% of ALS intake and was associated with poor gains in weight and length by the PFS and RF groups (relative weight and length gains were ALS>PFS>RF, P<0.05 for all comparisons); this suggests that the poor growth of RF rats when compared with PFS rats was due to factors other, than food intake. Serum IGF-I levels of 771±249 ng/ml in PFS rats were lower than levels of 1109±253 ng/ml found in the ALS group (P<0.05); this is consistent with the malnourished state of PFS rats. Serum IGF-I levels in RF rats (950±236 ng/ml) were not different from ALS or PFS levels despite the fact that RF rats gained less weight and length than either the ALS or PFS rats. We conclude that RF rats increase in length, use ingested calories more efficiently, and fail to develop marked insulin resistance when treated with met-hGH. We find that, in addition to poor food intake, other factors contribute to growth failure in this model of renal failure. Finally, we find that RF rats have normal levels of IGF-I, suggesting that low IGF-I levels are not a major cause of growth failure in rats with renal failure.