Effect of dopamine D3 receptor blockade on renal function and glomerular size in diabetic rats

Dopamine D-2-like receptors, including D-2, D-3, and D-4 receptors, are involved in the regulation of glomerular hyperfiltration due to diabetes mellitus. These hemodynamic alterations represent a risk factor for the later development of diabetic nephropathy. The aim of the present study was to determine whether the D-3 receptor subtype modulates the diabetes-induced increase in glomerular filtration rate (GFR) in rats. Renal function was studied in Sprague-Dawley rats 14 days after induction of a moderate diabetes mellitus (DM) by streptozotocin and in non-diabetic controls (CON). Rats were orally treated either with the peripherally acting, selective dopamine D-3 receptor antagonist BSF 135170 (BSF, 10 mg/kg per day for 2 weeks) or with vehicle (VHC). Perfusion-fixed kidneys were used for estimation of glomerular volume. In conscious rats, which were treated with BSF, the DM-induced increase in fluid intake, urinary output, and renal sodium excretion was significantly less pronounced than in the vehicle group (DM-VHC). In the clearance experiments, GFR in CON was about 0.84 +/- 0.04 ml/min per 100 g body weight. The DM-VHC group presented a significant glomerular hyperfiltration (1.09 +/- 0.04 ml/min per 100 g body weight). Treatment with BSF significantly lowered GFR towards levels of CON. The estimated glomerular volume was 0.73 +/- 0.03x10(6) mu m(3) in the CON-VHC group and 0.86 +/- 0.04x10(6) mu m(3) in the DM-VHC animals. Interestingly, treatment with BSF decreased the glomerular volume in both groups. Irrespective of BSF treatment, kidney wet weight related to body weight was about 36% higher in DM animals compared with CON animals. We conclude that dopamine D-3 receptors represent a target for the modulation of diabetes-induced glomerular hyperfiltration. Therefore, the results encourage the testing of the possible beneficial effects of long-term D-3 receptor blockade on the development of diabetic nephropathy.