Maintenance Of Normal Blood Pressure Research Articles

EFFECTIVE RENAL BLOOD FLOW, GLOMERULAR FILTRATION RATE AND TUBULAR EXCRETORY MASS IN ARTERIAL HYPERTENSION

Interest in the relation of renal function and arterial hypertension, recognized since the time of Bright, has been greatly stimulated by the experimental work of Goldblatt and his associates,¹who were able to produce permanent hypertension in animals by partial constriction of the main renal arteries. The experiments of Goldblatt and his co-workers have been successfully repeated in different ways by many authors, as cited by Goldblatt,²and the importance of normal renal circulation for the maintenance of normal blood pressure in animals appears to be an established fact. Page and his associates³and Muñoz and Braun-Menendez and their associates,⁴reviving the original work of Tigerstedt and Bergman,⁵have offered further evidence of the importance of the renal circulation in hypertension by demonstrating the production in the kidney of a pressor substance, which they have called angiotonin, or hypertensin. The amount of angiotonin produced is increased when

Does Renin Play a Role in the Maintenance of Normal Blood Pressure?

1. Bilateral nephrectomy under the above conditions increases the sensitivity of the dog to the pressor action of renin administered intravenously. 2. The renin content of the kidneys of dogs bears no relation to the blood pressure level of the animals. 3. Differences in the renin concentration of the kidneys of dogs and even between the 2 kidneys of the same dog, occur. 4. Stimulation of the splanchnic nerve produces no significant change in the renin content of the dog's kidney. 5. Hypotension as induced above does not alter significantly the renin concentration of the kidney of the dog. 6. There is no evidence at present for the possible rôle of renin in the maintenance of normal blood pressure.

THE URINARY EXCRETION OF A DEPRESSOR SUBSTANCE (KALLIKREIN OF FREY AND KRAUT) IN ARTERIAL HYPERTENSION*

While the explanation of the immediate mechanism causing persistent elevation of blood pressure has in recent years been greatly clarified in terms of increased arteriolar resistance, the underlying factors, with certain exceptions, which regulate arteriolar tonus are not clearly defined. Maintenance of normal blood pressure, together with adequate tissue nourishment, demands a nice physiologic adjustment between cardiac output, circulating blood volume and available vascular bed. Such adjustment conceivably may be mediated through nervous, chemical or hormonal influences acting either singly or in consonance. As regards their influence upon arteriolar tonus, while something is known of the regulatory activities of the nervous system, the possible importance of the chemical and hormonal influences remains obscure and offers a fertile field for investigation. It is probable that the ultimate answer to the question of arterial hypertension will be found in this field, and a large amount of both experimental and clinical study has been undertaken with that end in view. In general, such investigation has evolved along two main lines. The first has been an effort to detect a “warp” in the metabolism of patients with essential hypertension, by the qualitative and quantitative study of the chemical constituents of the tissues, body fluids and excretory products. No constant deviation from the normal has been established. The second line of endeavor has consisted in the evaluation of the physiologic importance of substances of both metabolic and secretory origin which have a direct influence upon the peripheral circulatory apparatus. Those substances which increase arteriolar tonus, of which adrenalin, pituitrin and methylguanadine are examples, have received the most attention. Numerous attempts to establish in patients with hypertension a constant superabundance of such substances, or an abnormal reaction of the vessel walls to them, have been inconclusive and the positive results so exceptional as to preclude trustworthy deductions. The importance of the depressor substances present in the body has received less study; yet, a priori, a disturbance in the balance between pressor and depressor elements, is a reasonable hypothesis by which to explain the pathologic elevation of blood pressure.