Removal of angiotensins from the systemic circulation

The extraction of α-angiotensin and its aminopeptidase-resiistant analogue β-angiotensin by the pulmonary, hepatoportal, femoral, and renal vascular beds was studied in normal anesthetized dogs and rats by comparing the systemic pressor responses to infusions into the afferent and efferent vessel of each organ. The extraction percentage of both peptides by the pulmonary circulation was negligible whereas it averaged 70% for α-angiotensin and 63% for the β-analogue in the other three systemic vascular beds studied. It is concluded that the main process responsible for the clearing of angiotensin from the systemic circulation is not the activity of circulating angiotensinases but rather occurs in the tissues.

Prognostic value of plasma renin activity in renovascular hypertension

Renin activity was measured in 248 plasma samples from 78 hypertensive patients with unilateral angiographic renovascular lesions. The humeral (brachial), the two renal, and the suprarenal or the infrarenal caval, or both, veins were sampled. Peripheral vein renin was poorly correlated with surgical success. Venous renin from the involved kidney was better but still failed consistently to predict postoperative benefit. Only in blood from the suprarenal portion of the vena cava were renin levels of considerable prognostic value (87% accuracy) in operated patients. Increases at this level seem to reflect more closely absolute increments in renin secretion rates, whereas increases limited to the venous blood from a stenosed kidney seem to stem mostly from reduced renal blood flow. It is concluded that determination of suprarenal renin deserves a larger scale investigation to define its place among the preoperative tests used for predicting renosurgical benefit in unilateral renovascular hypertension.