Renal kallikrein and hemodynamic abnormalities of diabetic kidney

Abstract

The relationship between renal hemodynamic abnormalities and renal kallikrein activity was studied in streptozocin-induced diabetic rats. Diabetic rats were either not treated with insulin and had plasma glucose levels >400 mg/dl (severely hyperglycemic diabetic [MD]) or were treated with 1.5–1.75 U/day protamine zinc insulin and had glucose levels of 200–300 mg/dl (moderately hyperglycemic diabetic [MD]). In SD rats, kidney tissue level and excretion of active kallikrein were reduced after 3 wk compared with age-matched nondiabetic control rats (tissue, 11.7 ± 1.9 vs. 20.5 ± 1.8 ng/mg protein, P <0.005; urine, 126 ± 12vs. 179 ± 10 μg/24 h, P <0.05). Glomerular filtration rate (GFR) was not significantly lower (2.77 ± 0.60vs. 3.02 ± 0.56 ml/min). In MD rats, kidney tissue level and excretion of active kallikrein were increased after 5 wk compared with age-matched nondiabetic control rats (tissue, 28.4 ± 1.3 vs. 23.3 ± 1.7 ng/mg protein, P < 0.05; urine, 289 ± 16 vs. 196 ± 13μg/24 h, P < 0.001). In MD rats, GFR and RPF were increased (3.80 ± 0.11 and 8.04 ± 0.17 ml/min, respectively) compared with control rats (3.22 ± 0.05 and 7.28 ± 0.09 ml/min, P < 0.001). Treatment of MD rats with a kallikrein inhibitor reduced GFR and RPF to levels similar to those of nondiabetic control rats. With recent evidence that kallikrein and kinins have a renal paracrine role in regulating vascular resistance, our findings suggest that altered kallikrein activity may contribute to the renal hemodynamic and filtration abnormalities in diabetes.