A comparison of the physicochemical properties of renins from the uterus and kidney of pregnant rabbit.

Renin from rabbit kidney and uterus was extracted and purified by combined gel filtration, affinity chromatography and preparative isoelectric focusing; specific activities were determined by radioimmunoassay methods. The characterization was carried out by molecular weight determinations, polyacrylamide gel electrophoresis and analytical isoelectric focusing. A single form of renin was obtained from kidney extracts (purification 87 000-fold). From uterine extracts, however, four fractions were separated (purification 94 000; 30 000; 47 000; 187 000-fold, respectively). These fractions possess the same molecular weight but differences in electrophoretic mobilities and in isoelectric points were observed. Only one uterine fraction was coincident with the renal fraction. The uterine enzyme possesses a higher specific activity. It must be regarded as a local product of the uterine wall with a molecular configuration different from that of the renal renin.