Effect of insulin-like growth factor I infusion on renal hypertrophy in experimental diabetes mellitus in rats.

Initial diabetic renal hypertrophy is preceded by a transient increase in kidney insulin-like growth factor I suggesting that insulin-like growth factor I may be implicated in diabetic kidney growth. The present study was undertaken to examine the effects of exogenous insulin-like growth factor I infusion on diabetic renal hypertrophy at a time when renal insulin-like growth factor I concentration had returned to normal and the initial steep kidney growth rate had diminished to a much slower rate. Groups of rats with diabetes duration of 5 days were infused s.c. for 4 subsequent days with equimolar concentrations of insulin-like growth factor I (36 nmol/day) or insulin (35 nmol/day). Insulin infusion lowered blood glucose to a normal level within 2 days and induced an average body-weight gain of 9.3 +/- 0.6 g/day. Insulin-like growth factor I infused diabetic rats maintained the original diabetic state with blood glucose levels comparable to those of 0.154 mol/l NaCl-infused diabetic rats, but had nevertheless an average body-weight gain of 6.8 +/- 1.0 g/day while untreated diabetic rats had a lower body-weight gain amounting to 3.3 +/- 0.8 g/day (p less than 0.01). The kidney weight at day 9 in untreated diabetic animals was about 25% greater than that of non-diabetic control animals, while in insulin-like growth factor I treated diabetic rats a further increase (p less than 0.05) was seen, amounting to 36% above control level. No increase was seen in the insulin-treated diabetic group.(ABSTRACT TRUNCATED AT 250 WORDS)