Additive increase in kidney insulin-like growth factor I and initial renal enlargement in uninephrectomized-diabetic rats.

The initial renal hypertrophy in experimental diabetes and in response to uninephrectomy is associated with renal accumulation of insulin-like growth factor I (IGF-I). Since the combination of diabetes and nephrectomy almost doubles the initial renal growth rate the aim of the present study was to investigate the kidney IGF-I levels in the combined situation in uninephrectomized diabetic rats. Three experimental groups were exposed to either unilateral nephrectomy, streptozotocin-diabetes or both conditions and for four days animals from each group were taken out for investigation. After 4 days the wet kidney weight increased from baseline by 31% (from 661 +/- 16 mg (SEM) to 866 +/- 27 mg) (P less than 0.01) in the uninephrectomized group, 32% (to 872 +/- 18 mg) (P less than 0.01) in the diabetic group and 46% (to 962 +/- 27 mg) (P less than 0.01) in the uninephrectomized-diabetic group. Kidney IGF-I concentrations were analyzed by radioimmunoassay and the increase from baseline on day 2 was 74% (from 262 +/- 12 ng/g (SEM) to 456 +/- 21 ng/g) (P less than 0.01) in the uninephrectomized group, 58% (to 414 +/- 18 ng/g) (P less than 0.01) in the diabetic group and 176 +/- % (to 722 +/- 56 ng/g) (P less than 0.01) in the combined group. Thereafter a decline in kidney IGF-I occurred in all groups, being normal at day 4 for the diabetic group, but still significantly higher in the uninephrectomized and uninephrectomized-diabetic groups compared to controls (P less than 0.05%).(ABSTRACT TRUNCATED AT 250 WORDS)