Purification and characterization of alkaline ribonuclease inhibitor from normal and nephrotic rat kidney compared to inhibitor from rat liver

Alkaline ribonuclease inhibitor has been purified from the kidney of control rats as well as from the kidney of nephrotic rats and the properties of the kidney inhibitor have been compared to those of the ribonuclease inhibitor obtained from the liver of normal control rats. For kidney inhibitor, the molecular weight (50,000), the electrophoretic mobility, the sensitivity to heat, to sulfhydryl reactants, and to tryptic digestion are all the same as those of liver inhibitor. The specific activity and properties of the purified inhibitor obtained from nephrotic kidney were the same as for inhibitor from control kidney, but the yield of inhibitor protein was three times greater from nephrotic kidney. Evidence for the view that there is an increased synthesis of ribonuclease inhibitor in nephrotic kidney is discussed.