On the role of renin in one-kidney, one-clip hypertension.

It is known that the renin angiotension system as it is usually understood is not the mediator of experimental one-kidney, one-clip (1K,1C) hypertension in animals. There is also ample evidence that the blood pressure of dogs and rabbits with this form of hypertension can be lowered by immunization with hog renin, which implies that renin is the mediator. In an effort to resolve this contradiction, we searched for a second hypertensive substance which we thought may have been present in the crude hog kidney extracts that had been used to immunize the hypertensive animals.

Incorporation of labeled renin into the tissues of the rabbit.

Our previous work has shown that pure hog renin, when injected into one-kidney, one-clip hypertensive rabbits elicits not only antirenin antibodies but also antibodies to what appears to be an altered form of renin (antigen M). Antiantigen M stains the cytoplasm of smooth muscle cells and certain other cells in tissues of normal and hypertensive rabbits. We now report studies in which pure 125I hog and rabbit renin have been infused into hypertensive rabbits for seven-day periods and the tissues subsequently examined for nondegraded radioactive components.

A new mechanism in one-kidney, one clip hypertension.

The renin-angiotensin system does not appear to be involved in the maintenance of elevated blood pressure in experimental one-kidney, one clip hypertension. Paradoxically, direct immunization with purified hog kidney renin lowers the blood pressure of rabbits with this form of hypertension. Antirenin antibodies were removed and the IgG fraction prepared from the plasma of such immunized rabbits.

Purification of hog kidney renin with immobilized monoclonal antirenin.

Spleen cells from mice immunized with partially purified hog kidney renin were fused with mouse myeloma cells to produce a stable monoclonal hybridoma cell line that synthesizes an antibody against renin. A single monoclonal antibody was chosen for study and has been produced in large quantity and purified by affinity chromatography on protein A-Sepharose. The antirenin, which belongs to the IgG1 subclass, exhibits anticatalytic activity against both hog and rabbit renin.

A comparison of the substrate specificities of cathepsin D and pseudorenin.

Cathepsin D, purified from hog spleen, releases angiotensin I from tetradecapeptide renin substrate and from protein renin substrates purified from hog and human plasma. However, the enzyme does not act on the naturally occurring renin substrate as it exists in plasma nor on purified substrate in the presence of plasma. Cathepsin D releases angiotensin I quantitatively from tetradecapeptide renin substrate and does not further degrade the angiotensin I on prolonged incubation.

Multiple forms of renin substrate in human plasma.

Renin substrate (angiotensinogen) in unfractionated human plasma has been shown to exist in multiple forms by DEAE-cellulose chromatography and isoelectric focusing. Two major and 5 to 6 minor peaks were resolved by using a descending pH gradient elution from DEAE-cellulose columns. The two predominant forms were eluted at or near pH 4.

New developments in our knowledge of the chemistry of renin.

Although the role of renin in hypertension continues to be incompletely defined, recent progress in the chemistry of renin has been considerable. Extensive purifications of hog kidney renin and the renin-like mouse submaxillary gland enzyme have been achieved. Various inhibitory peptides based on tetradecapeptide renin substrate have been useful in renin kinetic studies and in renin affinity chromatography.

Chronic one-kidney hypertension in rabbits. III. Renopressin, a new hypertensive substance.

The blood pressure of rabbits with chronic one-kidney hypertension can be lowered to normal by immunization with hog kidney cortex preparations that do not contain renin, thus providing evidence for a new factor essential for the maintenance of an elevated blood pressure. A search for the new factor has led to the discovery of a hypertensive substance which we have named renopressin. Subcutaneous injection of the new substance into normal rabbits produces a delayed, slow increase in blood pressure, and after a few days the development of a moderate hypertension which persists indefinitely.

Chronic one-kidney hypertension in rabbits. II. Evidence for a new factor.

The arterial pressure of rabbits with chronic one-kidney hypertension can be lowered to normotensive levels by direct immunization with preparations made from the cortex of hog kidneys. Hypertensive rabbits that are immunized with large amounts of renin may develop high plasma antirenin titers without affecting their blood pressure. Removal of renin by chromatography on columns of immobilized antirenin yields preparations with little or no renin.

Partial purification of a high molecular weight renin from hog kidney.

Previous investigators have reported finding a high molecular weight (HMW) renin in various species which is activated by acidification. Two laboratories have reported that a decrease in molecular weight of the renin accompanies the acidification step. This report describes the partial purification of an HMW renin from hog kidney extracts which had previously been acidified to pH 2.

The biochemistry of the renin-angiotensin system and its role in hypertension.

The renin-angiotensin system has an important role in maintaining elevated blood pressure levels in certain forms of experimental and human hypertension. Renin, an enzyme produced by the juxtaglomerular cells of the kidney, acts on a protein substrate found in the alpha 2-globulin fraction of the plasma to produce a decapeptide, angiotensin I. This decapeptide is not directly pressor, but on passage through the pulmonary circulation is converted to an octapeptide, angiotensin II, a very potent pressor substance which acts by causing constriction of arteriolar smooth muscle.

Kinetic properties of pulmonary angiotensin-converting enzyme. Hydrolysis of hippurylglycylglycine.

Some of the kinetic properties of angiotensin-converting enzyme (peptidyl-dipeptide hydrolase, EC 3.4.15.

Chronic one-kidney hypertension in rabbits. I. Treatment with kidney extracts.

An investigation into the mechanism that sustains the blood pressure in chronic one-kidney hypertension in rabbits was made using passive and active immunization with hog kidney extracts containing renin and with angiotensin antagonists. Seven hypertensive rabbits were passively immunized for extended periods with antiserum prepared in other rabbits. Antirenin levels were in the range of 1-3 units/ml.