RENAL TISSUE ANGIOTENSIN-II - RESPONSE TO INFUSIONS OF ANGIOTENSIN-I AND AN ANGIOTENSIN-CONVERTING ENZYME-INHIBITOR

A procedure for the collection, processing, extraction, separation, and measurement of renal tissue angiotensin II [ANG-(1–8)] is described. The arterial plasma and renal tissue concentrations of ANG-(1–8) were examined in anesthetized Sprague-Dawley male rats (10 to 12 weeks of age) given an intravenous saline infusion (group 1; n = 6), an intravenous bolus infusion of 0.5 μg angiotensin I (group 2; n = 6), or an intravenous bolus of an angiotensin-converting enzyme inhibitor (group 3; n = 6). Plasma and renal tissue were collected at the peak mean arterial pressure (MAP) response. The mean (± SEM) concentration of ANG-(1–8) in the group given the saline vehicle was 12 ± 2 fmol/mL in the plasma and 2.4 ± 0.3 pmol/g in the renal tissue. The angiotensin I bolus significantly increased MAP by 40%. Following the angiotensin I infusion, at the time of peak MAP response, the concentration of the circulating and renal tissue ANG-(1–8) were 12-fold and twofold higher, respectively, compared with the saline vehicle. The angiotensinconverting enzyme inhibitor significantly decreased MAP by 10% and decreased the circulating and renal tissue ANG(1–8) levels by 75% and 62.5%, respectively, compared with the saline vehicle. The rapid conversion of exogenous angiotensin I to ANG-(1–8) in renal tissue provides direct evidence that renal tissue can generate de novo ANG-(1–8) from a circulating precursor. Furthermore, plasma and renal tissue respond similarly to acute angiotensin-converting enzyme inhibition. © 1993, National Kidney Foundation. All rights reserved. All rights reserved.