Determination of renin in rats by radio-immune method, in kidney tissue of biopsy order of magnitude

Based on Haber's method a radio-immune assay was elaborated to determine renin content in 10 mg of kidney tissue. The principle of the method is to measure the angiotensine I labelled with 125I (specific activity 1000 μCi/μg) which develops from angiotensinogene as a substrate of renin. From the substrate some series of dilutions were prepared, the renin concentrations could be calculated from their saturation values (2-32 ng/ml renin measuring range). It was checked, that in the materials of the substrate only renin was responsible for the development of angiotensine I. The average renin level of 50 rats was 2.77+-0.43 U/mg protein determined by the method. (D.E.)