Bio-assay of circulating renin-like pressor material by isovolemic cross circulation

The renin-like pressor material present in blood under various experimental conditions was determined by isovolemic cross circulation using nephrectomized rats as assay animals and rats having different concentrations of renin in the kidney as "donor" animals. Cross circulation was established by connecting the femoral arteries of both animals with the corresponding femoral veins and maintaining a constant flow. In intact anesthetized rats, a "basic" concentration of renin-like pressor material is demonstrable in the blood which is not influenced by unilateral nephrectomy. In the rat made hypertensive by clamping one renal artery, leaving the other kidney untouched, an increase in circulating renin-like pressor material is demonstrable. In unilaterally nephrectomized rats in which the artery of the remaining kidney is clamped, the concentration of circulating pressor material is not elevated. In adrenalectomized rats, an increase of circulating pressor material coincides with an elevated concentration of renin in the kidneys. There is a good correlation between the concentration of renin in the kidney and of pressor material in the blood, while the level of circulating renin-like substance is not correlated with the height of blood pressure.