Intrarenal metabolism of angiotensin II.

This study investigated the intrarenal metabolism of circulating angiotensin II. Mean arterial pressure (MAP), renal hemodynamics, and the arterial, renal venous, and renal tissue concentrations of the angiotensin octapeptide [ANG-(1-8)] were examined following the constant intra-arterial infusion of tritiated angiotensin II [( 3H]ANG-(1-8)] in graded doses of 0.5, 2.0, and 2.5 ng.kg-1.min-1 in five uninephrectomized, anesthetized female dogs. The infusion of [3H]ANG-(1-8) had no significant effect on MAP, glomerular filtration rate, renal blood flow, or urine flow rate. The mean degradation rate of intra-arterially infused [3H]ANG-(1-8) was 72%. The net renal venous plasma concentration of ANG-(1-8) was greater than that predicted from the degradation rate of [3H]ANG-(1-8). High concentrations of ANG-(1-8) were measurable in all renal tissues. However, [3H]ANG-(1-8) was not detectable in any renal tissue. These observations suggest that ANG-(1-8) in the renal venous effluent was derived, in part, de novo from intrarenal generation. Likewise, renal tissue ANG-(1-8) was derived de novo from intrarenal generation.