Effects of ganglionic blocking agents, pressor and depressor drugs on renal hypertension

PRODUCTION OF ANTIRENIN TO HOMOLOGOUS RENIN AND ITS EFFECT OF EXPERIMENTAL RENAL HYPERTENSION

1. Procedures are described for the extraction and partial purification of dog renin, on a large scale, as well as for the acetylation of rat, rabbit, and dog renin. 2. Untreated homologous renin was not antigenic in rat, rabbit, or dog, but the acetylation of homologous renin made it antigenic. 3. Immunization of rats, rabbits, and dogs, with acetylated rat, rabbit, and dog renin, respectively, resulted in each case in the development of anti-renin to the homologous, untreated, as well as to the acetylated renin. 4. The progressive development of antirenin as a result of repeated, subcutaneous injections of acetylated dog renin, in a dog with experimental renal hypertension for more than 6 years, was accompanied by a correspondingly progressive fall of the mean arterial blood pressure to the prehypertensive level. This points up the important part played by the renin-angiotensin mechanism in the maintenance of the hypertension, even in the chronic phase of experimental renal hypertension.

Immunologic approaches to blockade of the renin-angiotensin system: a review

Several immunologic approaches to blockade of the renin-angiotensin system (RAS) have been reported, involving most of the proteins and peptides of the biochemical cascade: renin, substrate, angiotensins, and converting enzyme. None as yet has involved blockade of angiotensin II receptors. Earlier and more recent studies used passive transfer of heterologous antibodies or active immunization against RAS proteins and peptides. Passive transfers have been performed with both polyclonal antibodies and now with specific monoclonal immunoglobulins. The latter are better defined in affinity, quantity, and capacity to bind and thus inhibit the biologic activity of the antigen. Active immunization produced long-term blockade of part or all of the biologic activity of the system. The immunopathologic consequences of the use of antibodies raised against a self-antigen could be of interest in defining the predominant site of storage and secretion of the relevant protein and hence the respective roles of different tissues in the production of specific proteins in, for example, the vascular pulmonary bed for converting enzyme and renal arterial tree for renin. In all cases immunologic methods offer in vivo experimental models of short- or long-term RAS blockade that could be compared with pharmacologic methods, such as converting-enzyme inhibition, angiotensin II antagonists, and renin inhibitors.

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. An immunoaffinity column prepared from antibody coupled to Sepharose has been used in the purification of renin from hog kidney. Although renin is quantitatively adsorbed from solution, it can be eluted from the column under gentle conditions. The highly purified renin, with specific activity of 2122 Goldblatt Units/mg protein, exhibits both charge (pH 4.1 to 5.1) and size (38,000 to 42,700) heterogeneity. Hog kidney renin dissociates in the presence of sodium dodecyl sulfate (SDS) and mercaptoethanol to heavy and light chains with molecular weights of 33,700 and 5,800, respectively. In the presence of SDS, a small amount of a nw form of renin is observed with a molecular weight of 19,500 which retains activity on renaturation. The monoclonal antibody should be a useful tool for the study of the renin-angiotensin system and especially for the purification of renin. The hybridoma cell line used in this study (F-32 VIII C4) has been donated to the American Type Culture Collection.

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. Such preparations may be effective in lowering blood pressure although they do not elicit the formation of plasma antirenin and the rabbits remain sensitive to challenging doses of rabbit renin. The evidence suggests that an unknown substance is responsible for the development of a cross-reacting antibody that neutralizes an unknown factor that is essential for the maintence of an elevated blood pressure level in rabbits with chronic one-kidney hypertension.

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. In addition to its direct action which increases blood pressure, angiotensin II acts on the adrenal cortex to cause the release of the sodium-retaining hormone aldosterone. Recent evidence suggests that this action may be mediated by the heptapeptide, angiotensin III. Both renin and its protein substrate exist in multiple forms and renin may also exist as a high molecular-weight "pro-hormone," although the physiologic significance of these forms is not clear. The elucidation of the biochemistry of the renin-angiotensin system has provided us with inhibitors which allow the system to be blocked effectively in vivo. Thus, angiotensin antagonists such as Sar 1, IIe 8-angiotensin II and converting enzyme inhibitors such as BPP 9a (SQ 20881) have proved useful in the study of experimental and human hypertension.

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. Control experiments demonstrated that antirenin concentrations of 1.0 unit/ml or more eliminated more than 99% of the pressor response to renin. There was no lowering of blood pressure that could be attributed to the antibodies. No decrease in blood pressure was observed in 13 experiments in 7 rabbits given the angiotensin II antagonist 1-Sar-8-Ile-angiotensin II; infusion rates of 0.09-87 mug/min kg-1 were used for periods of a few hours up to 3 days. A reduction in blood pressure occurred in 16 of 19 rabbits immunized directly with extracts containing renin with specific activities of 9.6-757 GU/mg. Plasma antirenin titers correlated poorly with reductions in blood pressure. The blood pressure of 22 rabbits given equal amounts of protein without renin was unaffected. It is concluded that the elevation of blood pressure in rabbits with chronic one-kidney hypertension is not dependent on ciculating renin or angiotensin; rather, it results from the presence of renin in an extravascular location or from an unknown pressor substance.

The importance of central adrenergic neurones in renal hypertension in rabbits

1. Central nervous system adrenergic neurones were partially destroyed by injection of 6-hydroxydopamine (6-OHD) into the cisterna magna of normal rabbits and of rabbits with renal hypertension produced by bilateral wrapping of the kidneys with cellophane.2. Six weeks after renal manipulation, the mean arterial pressure of control animals was 122.1 +/- 2.4 mmHg while the pressure of rabbits which had been pre-treated with intracisternal 6-OHD was only 100.0 +/- 4.3 mmHg.3. Partial destruction of central adrenergic neurones by injection of 6-OHD into the cisterna magna produced a sustained lowering of arterial pressure in rabbits with established renal hypertension, whether this hypertension had been short (6 weeks) or of long duration (18 weeks).4. Adrenergic neurones in the central nervous system play a role in the development and maintenance of the raised arterial pressure in rabbits with renal hypertension.

Characterization of the renin-antirenin system

Rabbit antibody capable of neutralizing the pressor activity of the enzyme renin, derived from hog kidneys, was characterized with respect to type and capacity to react serologically. Three antirenin antibodies were detected, both a precipitating and nonprecipitating, neutralizing antibody as well as a neutralizing antibody capable of being absorbed by inactivated renin. The precipitating, neutralizing antibody was purified and used successfully in an assay for hog renin by means of a hemagglutination inhibition test. By immunofluorescent methods utilizing the purified antiserum, renin was found to be localized in the macula densa of the distal convoluted tubules and the juxtaglomerular cells of the afferent arteriole in both hog and dog kidneys.