Renoprotective effect of a dopamine D3 receptor antagonist in experimental type II diabetes.

Diabetic nephropathy is the leading cause of end-stage renal disease. Dopamine receptors are involved in the regulation of renal hemodynamics and may play a role in diabetes-induced hyperfiltration. To test this hypothesis, we investigated the renal effect of a dopamine D3 receptor antagonist (D3-RA) in hypertensive type II diabetic SHR/N-cp rats. Lean and obese SHR/N-cp rats were randomly assigned to D3-RA, angiotensin-converting enzyme inhibitor (ACE-i), or D3-RA+ACE-i treatment or control conditions. Treated animals were given the D3-RA A-437203 (10 mg/kg/body weight (BW)/day) or the ACE-i trandolapril (0.3 mg/kg BW/day) or a combination of both. At 6 months following perfusion, fixed kidneys were analyzed by morphological and stereological methods. Indices of renal damage (glomerulosclerosis, glomerulosclerosis damage index (GSI), tubulointerstitial and vascular damage), glomerular geometry and functional variables such as urinary albumin excretion, glomerular filtration rate, blood pressure, blood chemistry and BW were determined. The GSI (score 0-4) was significantly higher (P<0.05) in untreated diabetic animals (1.62+/-0.3) compared to nondiabetic controls (0.4+/-0.2) and the treatment groups (D3-RA: 0.31+/-0.12; ACE-i: 0.29+/-0.1; combination treatment: 0.12+/-0.01). Urinary albumin excretion (mg/24 h) was higher in untreated diabetic controls (102+/-19) compared to nondiabetic controls (31+/-12) and the treatment groups (D3-RA: 44+/-15; ACE-i: 41+/-13; combination treatment: 15+/-8). Mean glomerular volume was higher in untreated diabetic animals compared to nondiabetic controls and to the treatment groups. Desmin expression, a marker of podocyte damage, was elevated in untreated diabetic controls and diminished in all treatment groups. These data suggest that in a model of type II diabetes, the dopamine D3-RA had a beneficial effect on renal morphology and albuminuria, which was comparable in magnitude to that of ACE-i treatment.