Natriuretic response to saline load in one-kidney/one-clip hypertensive rats

Parameters of renal function were studied in conscious and anesthetized one-kidney (1K) and one-kidney/one-clip (1K-1C) rats. Effective renal blood flow (ERBF) was significantly lower in anesthetized 1K-1C rats than in conscious ones (12.1 +/- 1.6 vs. 16.4 +/- 1.2 ml/min). Renal function was evaluated in two-kidney (2K), 1K and 1K-1C unanesthetized rats. ERBF was lower in 1K and 1K-1C animals than in 2K rats. Glomerular filtration rate (GFR) and urinary sodium excretion (UNa.V) were not affected by uninephrectomy with or without clipping the renal artery. In 1K-1C rats, mean arterial pressure (MAP) increased from 100 +/- 2 to 140 +/- 1 mm Hg. Subsequently, the renal ability of unanesthetized rats to handle Na was studied by a sustained extracellular fluid volume expansion (EFVE) in all groups. During EFVE, MAP remained unchanged in the 2K and 1K groups and decreased significantly in the 1K-1C group, ERBF did not change and GFR increased to the same extent in all groups. The increase in UNa.V was 40% higher in 2K than in 1K or 1K-1C rats. These findings indicate that the relatively smaller natriuretic response to a saline load of 1K rats with or without a clip in the renal artery, as compared with 2K rats, could be ascribed to renal mass reduction. Finally, the study shows the advantage of performing studies of renal function in hypertension in conscious rather than anesthetized rats.