ON THE NATURE OF THE PRESSOR ACTION OF RENIN

1. Tachyphylaxis occurs when renin is repeatedly injected into dogs and cats regardless of whether they are normal, anesthetized, pithed, hepatectomized, suprarenalectomized, nephrectomized, or eviscerated. 2. The pressor response to renin in brief experiments is independent of the height of the arterial pressure or the presence of the suprarenals. Evisceration and large doses of ergotamine reduce the response. It is largely uninfluenced by pithing, intracisternal injection of renin, cocaine, strychnine, caffeine, and infusion of sodium bicarbonate or hydrochloric acid. It may be slightly increased by large blood transfusions or hepatectomy but the result is short lived. 3. There is no parallelism between the pressor responses to carotid sinus stimulation, adrenine, and tyramine on the one hand and renin on the other. 4. Section of the brain may be followed by depressor responses to renin. 5. Intracisternal injection of renin elicits no significant rise in blood pressure or other circulatory manifestations. 6. Continuous infusion of renin produces a prolonged rise of arterial pressure in normal and chronically suprarenalectomized dogs, but the pressure ultimately falls despite continued infusion. 7. Tachyphylaxis develops in the isolated rabbit's ear perfused with blood and small doses of renin. The same blood perfused through a second ear causes no vasoconstriction when renin is added. Addition of renin-activator restores the ability of renin to cause constriction. 8. Renin alone causes no vasoconstriction when perfused with Ringer's solution, but renin plus renin-activator restores activity. Tachyphylaxis does not develop when Ringer's solution is employed instead of recirculating blood. 9. Blood from animals made tachyphylactic by repeated injections of renin is lacking in activator and also fails to cause vasoconstriction in the rabbit's ear when renin and renin-activator are added. 10. Renin-activator is lost and tachyphylaxis develops more slowly during continuous infusion of renin. Blood pressure may fall after a period of renin infusion despite the pressure in the blood of excess renin. Injection of partially purified activator restores the activator content of the blood as demonstrated in the rabbit's ear, but no rise in arterial pressure occurs

THE VASOCONSTRICTOR ACTION OF PLASMA FROM HYPERTENSIVE PATIENTS AND DOGS

1. Plasma from the renal vein, femoral artery or vein of normal dogs and plasma from the femoral artery, femoral and antecubital veins of man cause little or no vasoconstriction when added in small amounts to blood from a bilaterally nephrectomized dog used as perfusing medium in an isolated rabbit's ear. 2. Plasma from the femoral vessels and antecubital vein of patients with essential hypertension, malignant hypertension, and chronic nephritic hypertension causes marked vasoconstriction under the same circumstances. The plasma of dogs made hypertensive either by constriction of the parenchyma by the scar of silk perinephritis or by constriction of the renal artery by a clamp also causes pronounced vasoconstriction. 3. Plasma from the renal vein of normal dogs produces little or no vasoconstriction, but that of hypertensive dogs elicits vasoconstriction but usually not so marked as that elicited by plasma collected from peripheral vessels. A sample of renal venous plasma from one hypertensive patient caused severe vasoconstriction, not quite so intense as that produced by the peripheral vein plasma. 4. Since renin is liberated into the renal vein in large amounts in hypertensive dogs and reacts with renin-activator to produce angiotonin and since the conditions of the experiment are such as to enhance greatly the sensitivity of the ear preparation to angiotonin, it is believed that the vasoconstriction is the result of the presence of angiotonin in the peripheral blood. 5. Since vasoconstriction occurs under the same experimental conditions with plasma from both hypertensive patients and dogs, this is considered cogent evidence in favor of the view that the chemical mediator of both is similar and is possibly angiotonin. 6. A method is presented which is believed will distinguish between plasma from patients with normal blood pressure and that from those with hypertension, and between plasma from normal dogs and that from dogs with experimental renal hypertension

OBSERVATIONS ON THE DEPRESSOR EXTRACTS OF HUMAN BLOOD AND ON THE VASCULAR ACTION OF EXTRACTS OF RABBIT AND DOG BLOOD

1. Alcoholic extracts of the plasma of rabbits obtained from arterial or venous blood differ from those of human plasma in having a marked depressor action on the blood pressure of anesthetized cats. This action is unantagonized on atropinization. Extracts of the plasma of dogs, on the other hand, are almost without vascular effect. 2. Ultrafiltrates of the plasma of rabbits are actively vasodepressor, while those of human and dog plasma are without action. 3. Extracts of the plasma of rabbits reduce the renal volume greatly and they have a relatively weak dilator action on the arteries of the periphery. These effects resemble those of adenylic acid more than those of histamine. 4. It is possible that the pressor-depressor substances of the blood are species-specific. 5. Human plasma, ascitic and spinal fluid which have been allowed to stand, yield extracts that are depressor and in their pharmacological action resemble closely extracts prepared from red blood cells and acetic acid extracts of tissues. Their constrictor effect on the kidneys is marked. 6. Histamine, choline, and adenosine depress the level of the blood pressure more effectively than they constrict the volume of the kidneys, while the reverse is true when adenylic acid is employed

PRESSOR SUBSTANCES FROM THE BODY FLUIDS OF MAN IN HEALTH AND DISEASE

1. Extracts of human blood plasma, ascitic and cerebrospinal fluids have been shown to contain a substance or substances which have a prolonged and powerful pressor action when injected into test animals. 2. The chemical properties of the substance suggest those of an organic base. It is extracted with alcohol, soluble in water and acetone, extracted from water by chloroform, and probably is but slightly heat-stable. The plasma colloids seem to hold the substance in a bound state since it does not appear in the ultrafiltrate and is liberated on coagulation of the colloids by alcohol. Coagulation alone of the blood does not cause the substance to be formed. 3. Its action suggests that its pressor effect is brought about by mediation of the central nervous system. This inference was drawn from the following observations. (a) The functional intactness of the central nervous system is essential in order that pressor responses be obtained. Unanesthetized animals exhibit greater vascular responses than do anesthetized. (b) Pithing animals completely abolishes the response. Progressive ablation of the brain to the level of the hind brain does not alter the response, but below this level, injury abolishes the activity of the extract. (c) Some substance in the extract sensitizes the mechanism responsible for the carotid sinus reflex. (d) There is no parallelism between the response to peripherally acting drugs and pressor extracts. (e) Removal of the adrenal glands does not affect its character. 4. The rise in blood pressure appears to be due especially to constriction of the arteries in the splanchnic region. 5. Assay of the pressor extracts is made difficult because of the dependence of the vascular response on the functional state of the central nervous system. The carotid sinus reflex and stimulation with carbon dioxide-air mixtures have proved most useful means for the estimation of this functional state. It has been pointed out that the vascular responses to extract, stimulation of the carotid sinus, and inhalation of carbon dioxide-air vary greatly during the course of an experiment on anesthetized animals. This natural history of the vascular responses has been described. 6. No evidence has been produced by the method employed that the amount of this pressor substance is increased in the blood or spinal fluid of patients with hypertension of varied pathogenesis (nephritic hypertension, essential hypertension, malignant hypertension, eclampsia, and pituitary basophilism)

THE EFFECTS OF RENAL HYPERTENSION ON THE VESSELS OF THE EARS OF RABBITS

1. The present experiments demonstrate by direct observation that peripheral arterioles in moat chambers in rabbits' ears constrict during the development of renal hypertension, and that they remain persistently constricted, although not sufficiently to interrupt the blood supply to the tissues. The arteriolar constriction in the hypertensive animals was not dependent upon nerves, since it occurred in newly formed arterioles which had probably never been supplied with nerves, as well as in older arterioles with a functional nerve supply. 2. No capillary constriction was observed during or following the development of hypertension, although the walls of the capillaries could be very clearly seen. Persistent hypertension was associated in two examples with increased sticking of leukocytes to the walls of the capillaries and venules, some emigration of leukocytes, and a few small hemorrhages. 3. During development of hypertension, new arteriovenous anastomoses were observed to appear in the chambers. 4. No evidence of change was noted in the viscosity of the blood or in the appearance of the blood corpuscles in the hypertensive rabbits. 5. The constriction of the arterioles during and following the development of hypertension closely resembled that produced by intravenous injections of angiotonin

SEPARATION AND CHARACTERIZATION OF HUMAN SERUM CHYLOMICRONS

Chylomicrons were separated by low and high speed ultracentrifugation from lipemic sera of human subjects in the absorptive phase. The final chylomicron preparation was free from other serum components and contained a small constant amount of protein, approximately 2 per cent of the chylomicron fraction. Electrophoresis, immunochemical analysis, and absorption experiments identified the protein component as derived from a mixture of beta and alpha1 serum lipoproteins. Large aliquots of an emulsion of serum freed of chylomicrons and coconut oil were incubated at 37°C. for 2 hours and ultracentrifuged as in the preparation of chylomicrons. The fat particles now showed the presence of minute amounts of beta and alpha1 serum lipoproteins in almost the same proportion as found in chylomicrons. "Finger prints" of delipidized samples of chylomicrons and particles from serum-coconut oil emulsion gave similar, although not identical patterns. The data on "clearing factor" activity corroborated the finding that serum alpha1 lipoproteins are contained in chylomicrons and particles from serum-coconut oil emulsion. These two lipide particles, partially delipidized, were both able to activate a "clearing factor" system in vitro, a property exhibited only by intact or partially delipidized alpha1 serum lipoproteins. Clearing activity was satisfactorily determined by using an emulsion of coconut oil mixed in agar as a substrate to give an opaque gel, in which the diffusing enzyme showed its activity by areas of clearing. The results obtained by this technique were in agreement with those based on fall in optical density and non-esterified fatty acid production. Chemical analysis of serum chylomicrons showed a concentration of cholesterol and phospholipides higher than could be accounted for by the attached beta and alpha1 serum lipoproteins. On the basis of these results the assumption is made that in the blood stream small amounts of serum lipoproteins, by a process of adsorption, form a complex with the absorbed triglycerides, cholesterol, and phospholipides, to produce chylomicrons

THE ACTION OF CRYSTALLINE PROTEOLYTIC ENZYMES ON ANGIOTONIN

Angiotonin was subjected to enzymatic digestion by crystalline carboxy-peptidase, chymotrypsin, trypsin, and pepsin. These enzymes were found to destroy it in vitro. Hydrogen ion optima and proteolytic coefficients for these reactions were determined and were found to be of approximately the expected magnitude for typical substrates. Regarding the purified crystalline enzymes as reagents, the experimental findings were interpreted on the basis of Bergmann's specificity studies. We were thus directed to the conclusion that angiotonin contains (1) a free terminal amino group, (2) a free terminal carboxyl group, (3) one basic amino acid residue which may be terminal but its carboxyl must be united in a peptide linkage, (4) one central dibasic amino acid residue in combination with an aromatic amino acid residue, (5) an aromatic amino acid residue which may be part of (4) and, if not part of (4) must be terminal with its carboxyl group in peptide linkage. The simplest compound satisfying these conditions is tyrosyl-arginylglutamyl-phenylalanine or a combination of amino acids with similar general characteristics

CHANGES IN THE PLASMA PROTEIN PATTERN (TISELIUS ELECTROPHORETIC TECHNIC) OF PATIENTS WITH HYPERTENSION AND DOGS WITH EXPERIMENTAL RENAL HYPERTENSION

The plasma protein pattern of patients with uncomplicated essential hypertension showed only slight variations from the normal while that of patients with severely malignant hypertension showed marked shifts. The fibrinogen and β-globulins were usually elevated beyond the normal range and the albumin decreased. In less severely malignant hypertension, the changes were less marked. In dogs with experimental renal hypertension, the γ-globulin level was greatly elevated, and in one animal exhibiting the malignant syndrome β-globulin and fibrinogen were also increased. Elevation of β-globulin seems in some manner associated with the occurrence of severe vascular disease

THE LIBERATION OF RENIN BY PERFUSION OF KIDNEYS FOLLOWING REDUCTION OF PULSE PRESSURE

1. Isolated dogs' kidneys have been perfused with defibrinated blood under hemodynamic conditions similar to those in the body. Under these circumstances blood flow, urine secretion, and oxygen consumption are well maintained, but urea clearance is low. Renal venous blood collected initially and at the end of 3 or more hours of perfusion exhibited no difference in vasoconstriction properties when perfused along with renin or renin-activator through an isolated rabbit's ear. 2. Reduction of pulse pressure by constricting the renal artery may be performed without reducing mean pressure significantly. Impairment of urea clearance and rate of urine secretion follow, and oxygen consumption is slightly reduced. 3. After an hour or more of perfusion with reduced pulse pressure, gradual rise in mean renal arterial pressure distal to the clamp and reduction of blood flow occur. 4. Renal venous blood collected after about one hour of perfusion with reduced pulse pressure differs from that collected before reduction of pulse pressure in that it causes intense vasoconstriction when perfused with renin-activator through an isolated rabbit's ear. 5. Perfusion of a dog's hind leg under similar circumstances does not cause this change in the venous blood to occur

A KINETIC ANALYSIS OF THE RENIN-ANGIOTONIN PRESSOR SYSTEM AND THE STANDARDIZATION OF THE ENZYMES RENIN AND ANGIOTONASE

The physicochemical background of the renal vasporessor system (renin-renin-substrate, angiotinin, angiotonase) is given. The formation and destruction of angiotonin is shown to consist of two consecutive reactions, both of which follow the laws of first order kinetics. Each reaction was studied separately and its reaction constant found to be proportional to the enzyme concentration. Hence these constants should be used to express the activity of the enzymes, renin and angiotonase. The over-all reaction of a mixture of renin and angiotonase such as occurs in kidney extracts with the α-globulin fraction of serum, viz., rapid increase followed by a slow decline in angiotonin concentration, was found experimentally to correspond closely to the theoretical values calculated for such a reaction. The curve obtained also satisfyingly explains the characteristic pressor response to the intravenous injection of renin. An accurate method for the determination of renin in the presence of angiotonase is presented