INTRARENAL HEMODYNAMIC AND GLOMERULAR RESPONSES TO INHIBITION OF NITRIC-OXIDE FORMATION IN RABBITS

1. The renal effects of inhibiting nitric oxide (NO) formation using N-nitro-L-arginine (NOLA, 20 mg kg(-1)) were examined using micropuncture techniques in pentobarbitone-anaesthetized rabbits. 2. Renal vascular resistance doubled from 2.7 +/- 0.5 to 5.0 +/- 1.1 mmHg ml(-1) min(-1) after NOLA (P < 0.01), with similar percentage increases in both pre- (149 +/- 38%, P < 0.01) and postglomerular (158 +/- 42%, P < 0.01) resistance. 3. Glomerular capillary pressure rose from 33 +/- 1 to 40 +/- 1 mmHg after NOLA (P < 0.01) but despite this, glomerular filtration rate (GFR) and single nephron glomerular filtration rate did not significantly change. 4. Blood pressure increased 18 +/- mmHg (P < 0.001) within 10 min of NOLA administration and remained near this level for the next 90 min. 5. The glomerular ultrafiltration coefficient (K-f) decreased significantly from 0.085 +/- 0.022 to 0.035 +/- 0.006 nl s(-1) mmHg(-1) (P < 0.05). 6. Urine flow and sodium excretion increased markedly (26 +/- 9 to 337 +/- 102 mu l min(-1) and 5 +/- 2 to 342 +/- 12 mu mol min(-1) respectively, (P < 0.001)) and sodium fractional excretion rose from 1.0 +/- 0.3 to 8.0 +/- 2.2% (P < 0.01). 7. Thus, administration of NOLA to rabbits caused vasoconstriction of both pre- and postglomerular vessels, diuresis and natriuresis without significant change in GFR, and a reduction in K-f. The results suggest that NO may play an important role in the regulation