Responses of active and inactive plasma renin and changes in urinary kallikrein and plasma prekallikrein to various conditions in normal subjects

Dynamic changes in plasma inactive renin levels in Bartter's syndrome after administration of captopril and angiotensin II

Changes in plasma active and inactive renin concentration (ARC and IRC) after captopril administration and angiotensin II (AII) infusion were studied in six patients with Bartter's syndrome. A single oral dose of captopril (8-25 mg) lowered the blood pressure and increased both ARC and IRC. AII infusion elevated blood pressure, suppressed ARC and increased IRC. In this syndrome of high renin levels, infused AII appeared to increase inactive renin secretion by reducing its conversion to active renin. On the other hand, an acute fall in AII levels and/or renal perfusion pressure by captopril increased both active and inactive renin. This indicates that the increase in the secretion of inactive renin, stimulated by captopril, might exceed any increase in its conversion to active renin in patients with Bartter's syndrome, in whom the production of renin is accelerated, and conversion of inactive renin to active renin probably already operates near its maximum.

Effects of enalapril maleate on plasma level of inactive renin in renovascular hypertension

Changes in plasma levels of active and inactive renin after the treatment with enalapril maleate (MK-421), a new angiotensin converting enzyme inhibitor, were studied in five patients with renovascular hypertension (RVH) due to unilateral renal artery stenosis. The dosage was increased when the blood pressure (BP) was not normalized for more than 3 days. Blood sampling was performed before, and 5 hours and 24 hours after the first administration, and on the 3rd day with each dosage. Active and inactive renin concentrations (ARC and IRC) showed a reciprocal change in 4 cases, 5 hours after the first dose. In the chronic treatment, ARC and IRC before the morning dose did not change apparently until the BP was normalized, when both ARC and IRC were evidently increased. It was suspected that a conversion from inactive to active renin may occur in the patients with RVH, when the active renin secretion is stimulated suddenly by the first dose of MK-421. The chronically diminished perfusion pressure in the kidney may stimulate the secretion of inactive renin, but the decrease in endogenous angiotensin II may not.

Synchronous changes in active and inactive renin secretion after furosemide in patients with primary aldosteronism

Changes in plasma active and inactive renin concentrations (ARC and IRC) were measured in 10 patients with primary aldosteronism (PA) due to adrenal adenomas. Before the resection of adrenal adenomas, venous blood samples were taken at supine resting state, after 1-hour standing and 30 min. after furosemide injection and these samplings were repeated after surgical treatment. Plasma inactive renin was measured after activation with trypsin. Before the treatment ARC and IRC did not change by standing or furosemide. After the treatment, however, ARC was increased clearly by standing or furosemide, and IRC was also increased by furosemide injection. Both ARC and IRC at supine resting state were increased after the surgery. When the renin-angiotensin system is suppressed chronically by the over-produced aldosterone in patients with PA, not only active but also inactive renin secretions are suppressed, and fail to respond to orthostasis or furosemide. The secretion of IR could be stimulated after the removal of aldosteronoma.

Studies on the active and inactive renin in renovascular hypertension

Active and inactive plasma renin concentrations (ARC and IRC) from both renal veins and the femoral artery, and the molecular weight (MW) of active and inactive renin (AR and IR) from both renal veins were measured in 6 patients with renovascular hypertension due to unilateral renal artery stenosis. Venous ARC on the affected side was higher than that on the unaffected side and arterial ARC. In 4 patients ARC increased and IRC decreased after circulating through the stenotic kidney, while in the other 2 cases venous IRC on the stenotic side was higher than arterial IRC. The MW of AR on the stenotic and non-stenotic sides were 40000-48000 and 45000-48000, respectively, and those of IR varied from 45000-53000 and 48000-55000, respectively. These values seem to be smaller than those of normal subjects. The renin molecule may be small immediately after the release from the kidney and become larger in the circulation. In 3 cases, whose ARC increased and IRC decreased after passing through the stenotic kidney, AR and IR from the stenotic kidney were smaller than those from the non-stenotic kidney. Some mechanism of AR and IR molecule reduction may work in the stenotic kidney to activate IR.

Effect of prostacyclin infusion on active and inactive renin release in the isolated perfused kidney

The effect of prostacyclin infusion into the renal artery of the isolated perfused hog kidney on the release of active and inactive renin was investigated. Infusion of prostacyclin at a rate of 0.1 microgram/min resulted in a significant increase (p less than 0.01) in active renin and a significant fall (p less than 0.01) in inactive renin. Prostacyclin also increased urinary kallikrein excretion (p less than 0.05). The results indicate that the kidney secretes not only active renin but also inactive renin, and suggest that prostacyclin stimulates the conversion of inactive renin to the active form through the activation of the renal kallikrein system.