An inactive renin in human plasma.

Normal human plasma contains an active form of renin that is activated by acidification to pH 3.0 and comprises 56% of the total renin. In our study, inactive renin was also present in plasma from five anephric persons, and the proportion of active to inactive renin in these subjects was similar to normal. Plasma from normal pregnant women contained increased concentrations of inactive renin and the proportion of inactive renin was raised to around 66%. Plasma from persons with renal hypertension contained varying amounts of inactive renin but the mean percentage (35%) was lower than normal. An infusion of saralasin sufficient to lower the blood pressure in five subjects with renal hypertension resulted in a rise in active renin concentration but no change in the concentration of inactive renin. Plasma angiotensin II correlated with active renin but not with inactive renin, suggesting that the inactive renin does not produce angiotensin II in vivo.