Studies on the Activation and Molecular Weight of Inactive Renin in Human Plasma

SUMMARY The mechanism of activation of inactive renin was studied in normal human plasma. The molecular weight of active renin and those of inactive renin before and after activation were analyzed by sephadex gel filtration. Active renin of human plasma had a molecular weight of 48,000 ± 1000. Trypsin treat-ment and cold treatment activated inactive renin of a molecular weight of 54,000 ± 1000. The inactive renin apparently did not change its molecular weight after activation. "Cryoactivation " of inactive renin was possi-ble only when whole plasma was used. When the whole plasma was fractionated by gel filtration, cryoactiva-tion was not observed in any of the fractions. Cryoactivation requires certain plasma factors) contained in some fractions. Plasma kailikrein is likely to be a major factor required for the cryoactivation of inactive renin, whereas some other factors may also participate in this mechanism. (Hypertension 2: 680-685, 1980) KEY WORDS • inactive renin • trypsin • cryoactivation • plasma kailikrein THE PRESENCE of inactive renin in humanplasma and its activation has been reportedby many investigators. The occurrence of inactive renin was also shown in human amniotic fluid.1 An inactive form of renin "prorenin " in human plasma can be activated during storage at a lo