Intravertebral ANG II effects on plasma renin and Na excretion in dogs at constant renal artery pressure.

Studies were performed to determine whether intravertebral angiotensin II infusion (iva ANG II) decreases renin release by increasing renal perfusion pressure (RPP) and to investigate possible effects of iva ANG II on renal function. RPP was electronically servocontrolled in 12 conscious dogs equipped with chronic vascular catheters and a suprarenal aortic balloon constrictor while iva ANG II was infused bilaterally for 60 min at 0.33 ng.kg-1.min-1. Without servocontrol, iva ANG II increased mean arterial pressure (MAP) from 101 +/- 4 to 106 +/- 5 mmHg, urine flow (V) from 0.36 +/- 0.03 to 0.45 +/- 0.04 ml/min, and sodium excretion (UNaV) from 36.2 +/- 7.0 to 62.7 +/- 6.6 mumol/min. Plasma renin activity (PRA) decreased from 6.9 +/- 0.7 to 5.0 +/- 0.6 ng ANG I.ml-1.3 h-1. With servocontrol, iva ANG II increased MAP from 102 +/- 4 to 109 +/- 5 mmHg while RPP remained constant with a variation of less than +/- 1 mmHg. PRA did not change significantly (5.9 +/- 0.3 to 7.0 +/- 0.7 ng ANG I.ml-1.3 h-1). V decreased from 0.33 +/- 0.02 to 0.26 +/- 0.01 ml/min, and UNaV decreased from 49.0 +/- 5.7 to 29.7 +/- 4.4 mumol/min. The data provide evidence that iva ANG II decreases renin release by increasing RPP and stimulating the renal baroreceptor and/or the macula densa mechanisms. In addition, at constant RPP, ANG II exerts a central action to decrease UNaV.