Evaluating hyperfiltration with glycine in hypertensive rats with renal ablation

Hypertension-induced renal damage is mediated by increased glomerular pressure and flow. These alterations have been evaluated by the renal response to protein or amino acids. To test this assumption, we studied glomerular hemodynamic responses to glycine infusion in rats with reduced renal mass, with and without Goldblatt hypertension. The left kidney was ablated by two thirds in 12 rats, and in 5, hypertension was induced by clipping the right renal artery. Seven normal, unmanipulated rats served as controls. Micropuncture was performed in the left kidney during control and 15% glycine infusion periods, 45 days after surgery. Arterial pressure was higher in hypertensive rats (160.3 mm Hg) than in controls (103.8 mm Hg) and rats with renal ablation (125 mm Hg; p less than 0.05). Higher values of single-nephron glomerular filtration rate and single-nephron plasma flow in rats with renal ablation (63.0, 223.7 nl/min) and hypertension (46.1, 239.7 nl/min) than in controls (28.8, 94.9; p less than 0.05) demonstrated the presence of hyperfiltration. However, glomerular pressure was elevated only in hypertensive rats (40.1 mm Hg), when compared to controls (32.7 mm Hg; p less than 0.05) and rats with renal ablation (33.4 mm Hg; p less than 0.05). Glycine increased single-nephron glomerular filtration rate and single-nephron plasma flow in control rats by 76 and 65%; rats with renal ablation had only partial responses, 35% and 23%, respectively, whereas in hypertensive rats the response was completely abolished. Glycine detected hyperfiltration and unmasked a dysfunction of preglomerular vessels that was greater in hypertensive rats and could contribute to the rise in glomerular pressure and flow and thereby to glomerular damage.