Adrenergic blockade in diabetic and uninephrectomized rats: Effects on renal size and on renal and urinary contents of epidermal growth factor

The present study reports on the effects of adrenergic blocking agents on t he renal growth and on the renal content and urinary excretion of epidermal growth factor (EGF) in streptozotocin-induced diabetic or uninephrectomize d rats. Diabetic and uninephrectomized rats were allocated to groups treate d with either saline or adrenergic antagonists and compared to controls and sham-operated controls, respectively. 24-hour urine samples were obtained on days 7, 14, and 21 and renal tissue samples on day 21. The 24-hour urina ry excretion of EGF from controls and saline-treated diabetic rats was comp arable. In adrenergic antagonist treated diabetic rats, it was reduced by a t feast 40% throughout the study period. Uninephrectomy caused a 50% reduct ion in the urinary excretion of EGF. This was not influenced by treatment w ith an adrenergic antagonist. After 3 weeks, saline-treated diabetic rats h ad an increase of 33% in kidney weight when compared to controls. The adren ergic antagonist treated diabetic groups had a significantly lower increase of 15%. Postnephrectomized renal growth was not affected by adrenergic ant agonists. The total renal content of EGF was comparable in the saline-treat ed diabetic group and the control group, but was reduced by approximately 5 0% in the kidneys from the adrenergic antagonist treated diabetic groups. R enal EGF mRNA levels were also reduced in adrenergic antagonist treated dia betic rats. In contrast to diabetes, the renal growth following nephrectomy was not affected by adrenergic blocking agents. These results provide evid ence for fundamental differences between diabetes-related renal growth and that observed in compensation to nephrectomy and suggest a connection betwe en adrenergic activity, renal growth, and EGF in diabetes.