Effects of stimulation of renin release on trypsin-activable renin in rat plasma

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Abstract
Little information is available concerning inactive renin in rat plasma. A renin assay method was now developed for measurement of active and inactive renin in approximately 0.1 ml rat plasma. Trypsin treatment of plasma (5.0 mg trypsin/ml plasma for 5 min at 0.degree. C) to maximally increase the rate of angiotensin I generation did not alter the Km or pH optimum of the renin reaction. Utilizing trypsin, 79 .+-. 6% of the total renin (acive + inactive) in normal rat plasma is in the inactive form. In vivo stimulation of renin by restraint stress induces a reciprocal change in active and inactive plasma renin, and exposure of animals to ether elevates active and total renin, while inactive renin shows a small but nonstatistical decline. Although a parallel disappearance of active and inactive renin is observed after bilateral nephrectomy of the pentobarbital-anesthetized animal, complete occlusion of the renal arteries and veins after ether-induced renin stimulation results in a significant increase of inactive renin. Apparently there is a possibility of formation of inactive renin from the active enzyme in high renin states. The balance of active and trypsin-activable renins in rat plasma may be dependent on not only the method but also the degree of in vivo renin stimulation.