Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.23.15 (renin)
 35,795 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. Complementing the work of Gervitz R. K., Hiraichi E., Fichman M. and Lavras A. A. C. Comp. Biochem. Physiol. 86A, 503-507 (1987), conditions have been established for measuring plasma renin activity (PRA) of the venomous snake Bothrops jararaca (Bj). 2. It corresponded to 115.9 +/- 11.5 ng equivalents of angiotensin II (AII) per ml of plasma (N = 13). 3. PRA did not increase when Bj plasma was submitted to acid-cryo-trypsin Bitis arietans venom activation of inactive renin. 4. This may indicate either absence of inactive renin in this plasma or lack of its activation, due to the already demonstrated (Nahas L., Kamiguti A. S., Betti F., Martins I. S. S. and Rodrigues M. I., Comp. Biochem. Physiol. 69A, 739-743, 1981; Prezoto B. C., Hiraichi E., Abdalla F. M. F. and Picarelli Z. P., Comp. Biochem. Physiol. 99C, 135-139, 1991) absence of factor XII.
 ...
PMID:Active and inactive renin in the plasma of the snake Bothrops jararaca. 135 20

Vasopressin is actively involved in the regulation of blood pressure to the same degree as catecholamines and the renin angiotensin aldosterone system are, especially in stressful situations. Vasopressin induces and increase in blood pressure when mechanisms buffering its potent vasoconstrictor effect are altered. Vasopressin binds to specific membrane receptors classified into two main types. The V1 receptors found in blood vessels, platelets and hepatocytes are linked to two intra-cellular messengers, namely 1,2 diacylglycerol and 1,4,5 inositol triphosphate which stimulate protein kinase C and calcium-calmodulin kinase in the presence of calcium. V2-renal receptors stimulate the production of cyclic AMP which activates protein kinase A. Subsequently, the actin network is altered and particles containing pores agregate at the cell surface to produce water molecules reabsorption. Vasopressin modifies human hemostasis via platelet aggregation, stimulation of the three fractions of factor VIII, of factor XII and of fibrinopeptide A. These properties were used to treat hemostasis abnormalities seen in Von Willebrand's disease and hemophilia. There is a feed-back loop between vasopressin and the atrial natriuretic factor: vasopressin stimulates atrial natriuretic factor release via a V1 action whereas the atrial natriuretic factor reduces vasopressin release and inhibits vasopressin antidiuretic action.
 ...
PMID:[Vasopressin, the antidiuretic hormone]. 295 73

A linkage between prorenin, renin, and intrinsic coagulation systems has been suggested recently. We studied the behavior of renin, prorenin, and kallikrein in a patient affected by congenital factor XII deficiency. Captopril test, upright posture, and furosemide administration provoked in our patients changes of renin and prorenin similar to those found in normal and hypertensive subjects. Unchanged kallikrein levels confirmed that no interaction between prorenin activation and factor XII-kallikrein system appears to be present.
 ...
PMID:Captopril-induced changes on active and inactive renin in a patient with factor XII congenital deficiency. 389 36

The active fragment derived from factor XII (factor XIIf) was purified from human plasma and administered intravenously to normotensive conscious rats. Factor XIIf-mediated hypotension was dose-dependent and augmented by pretreatment with captopril, an inhibitor of the angiotensin I- and bradykinin-processing enzyme. In contrast, factor XIIf-induced hypotension was not enhanced by blockade of the renin-angiotensin system by saralasin, a competitive antagonist of angiotensin II at the vascular receptor level. These results suggest that factor XIIf-mediated hypotension is due to the formation of bradykinin.
 ...
PMID:[Role of bradykinin in hypotension induced by the active factor derived from factor XII]. 609 10

Acid-pretreated normal human plasma generates renin activity at 0 degree C and neutral pH by the activation of prorenin. The activation is caused by kallikrein generated from prekallikrein by activated factor XII. Nonacidified plasma also generates renin at 0 degree C, but at a lower rate (cold-promoted activation). In normal plasma, 14% +/- 1% of prorenin (mean +/- SEM, n = 30) was activated during incubation at 0 degree C for 7 days (range 6% to 26%). Cold-promoted activation of prorenin was within the normal range in plasma deficient in factor XI, X, IX, VIIIC, VII, V, prothrombin, or high mol wt kininogen. Cold-promoted activation of prorenin was less than or equal to 1% in plasma deficient in factor XII or prekallikrein. Reconstitution of these plasmas with highly purified factor XII or prekallikrein restored normal prorenin activation. Correction of high mol wt kininogen deficiency had no effect. Thus cold-promoted activation of prorenin depends on the presence of factor XII and prekallikrein, whereas the other clotting factors are not essential. The influence of the inhibitors C1 esterase-inhibitor, alpha 2-macroglobulin, antithrombin III, and alpha 1-antitrypsin on the activation of prorenin was studied in factor XII-deficient plasma from which one or more of these inhibitors had been selectively removed by immunoadsorption. Factor XII was subsequently added, and the generation of renin at 37 degrees C was observed after complete factor XII-high mol wt kininogen-mediated activation of prekallikrein induced by dextran sulfate. No activation of prorenin was observed at 37 degrees C after depletion of C1 esterase inhibitor, alpha 2-macroglobulin, antithrombin III, or alpha 1-antitrypsin. When prekallikrein was activated in plasma depleted of both C1 esterase-inhibitor and alpha 2-macroglobulin, 6% of prorenin was activated in 2 hours at 37 degrees C. After additional depletion of antithrombin III, the activation increased to 47%. These results indicate that the contact activation system is capable of activating prorenin in plasma at physiologic pH and temperature when the three most important kallikrein inhibitors, C1 esterase-inhibitor, alpha 2-macroglobulin, and antithrombin III, are absent.
 ...
PMID:Prorenin-renin conversion by the contact activation system in human plasma: role of plasma protease inhibitors. 636 96

Cryoactivation of human plasma 'prorenin' was followed for 24 h at -4 degrees C. Chromogenic assays were used to determine factor XII (FXII), FXIIa, prekallikrein and kallikrein in relation to the observed cold-induced increase in plasma renin activity (PRA). Bradykinin activity was also determined using the rat uterus bioassay. PRA increased rapidly and became significantly higher after just 6 h of cryoactivation, by which time prekallikrein had almost disappeared, while kallikrein and kinin levels increased. In contrast, FXII did not change notably, but some FXIIa was indeed formed. The bacteriostat neomycin sulphate did not affect the course of cryoactivation, but did block the dextran sulphate- and kaolin-induced activation of prekallikrein and FXII respectively, and was therefore omitted. Thus cryoactivation of prorenin is accompanied by, and may depend upon, the activation of FXII and prekallikrein, supporting other evidence in favour of this hypothesis.
 ...
PMID:Factor XII and prekallikrein-kallikrein-kinin in the cryoactivation of human plasma prorenin. 636

The contact phase of blood coagulation in a group of patients suffering from essential hypertension was studied before and after captopril administration. The baseline levels of factor XII, factor XI and plasminogen were significantly higher than in normals and correlated with baseline diastolic blood pressure levels. On the contrary, plasma prekallikrein was not significantly different from normal. These results suggest the presence of a hypercoagulable state in essential hypertension. After captopril administration, factor XII, factor XI and prekallikrein rapidly decreased, perhaps as a consequence of the drug's effect on the vascular endothelial surface. There was no correlation between the changes of active and inactive renin and the changes of prekallikrein and plasminogen levels. Our data do not support the view that factor XII-plasma kallikrein or plasmin dependent pathways are involved in the activation of inactive renin in vivo. Captopril, by provoking rapid pressure changes, appears to be able to affect the clotting system.
 ...
PMID:The contact phase of blood coagulation and renin activation in essential hypertension before and after captopril. 638 34

Activation of prorenin in the neutral phase after pH 3.3 dialysis of human plasma depends on clotting factor XII-initiated prekallikrein to kallikrein conversion. Acid dialysis may be necessary for destroying kallikrein inhibitors or rendering prorenin susceptible to attack by kallikrein. If the latter possibility proves true, it is difficult to see how the factor XII-kallikrein pathway could activate prorenin in vivo. Plasma prorenin was therefore separated from active renin and from the protease inhibitors alpha 2-macroglobulin, C1-inactivator, alpha 1-antitrypsin, inter-alpha-trypsin inhibitor, and antithrombin III by gel filtration on Sephadex G-100 and affinity chromatography on Blue Sepharose CL-6B at neutral pH. The resulting prorenin preparation could be activated at pH 7.5 by highly purified human plasma kallikrein, which was prepared from prekallikrein by activation with active factor XII fragment beta-factor XII a. Activation proceeded at 4 and 37 C at a kallikrein concentration of 2 micrograms/ml, which is approximately 5% of the prekallikrein concentration in normal plasma. It appears that an acid-induced conformational change of the prorenin molecule is not required for its activation by plasma kallikrein.
 ...
PMID:Plasma kallikrein-mediated activation of the renin-angiotensin system does not require prior acidification of prorenin. 645 40

Inactive plasma renin is converted into an active form of renin during dialysis of plasma against a pH 3.3-buffer. This form of renin is inactivated at neutral pH. When plasma, after acid-dialysis, is kept at neutral pH a different form of active renin is generated, which remains active. The irreversible activation of prorenin depends on factor XII-initiated kallikrein formation. C1-inhibitor (C1-INH) and alpha 2-macroglobulin (alpha 2M) can be selectively denaturated by treatment of plasma at low pH values to which kallikrein and renin are resistant. After denaturation of C1-INH at pH 4-5, factor XII becomes capable of activating prekallikrein. The kallikrein that is formed after restoration of pH is complexed with alpha 2M. This complex has little activity towards natural protein substrates including prorenin. alpha 2M is denaturated at pH 3-4 and, as a consequence, kallikrein that is formed after restoration of pH is not complexed with alpha 2M. This kallikrein is able to attack both high-molecular weight kininogen and prorenin as manifested by the generation of bradykinin-forming and angiotensin-forming activities. These observations show a crucial role for C1-INH and alpha 2M in prorenin activation and explain, at least in part, why the pH of the acid-treatment step has to be less than 4 before irreversible activation of prorenin at neutral pH can occur.
 ...
PMID:Role of intrinsic inhibitors in acid-activation of inactive plasma renin (prorenin). 675 86

1. Inactive renin in human plasma can be activated by pH 3.3-dialysis (generation of acid-activated renin), by clotting factor XII-mediated prekallikrein to kallikrein conversion after pH has been restored to neural (generation of acid-kallikrein-activated renin) or by the addition of trypsin (generation of trypsin-activated renin). 2. Natural active renin, acid-kallikrein-activated renin and trypsin-activated renin behave similarly during affinity chromatography on Blue-Sepharose CL-6B and during gel filtration on Sephadex G-100. They also show similar reaction kinetics with similar pH-optimum curves when acting on sheep renin substrate. 3. Acid-activated renin is different. It is retained on Blue-Sepharose columns and it is inactivated at neutral pH during incubation at 37 degrees C. This contrasts with the other forms of renin activated in vitro and with natural active renin. The pH-optimum curve of acid-activated renin, when acting on sheep renin substrate, is also different from that of the other forms of active renin. 4. It is to be proven that the renins generated in vitro by neutral serine proteinases are identical with natural active renin, but clearly they bear more resemblance to natural renin than acid-activated renin does. Our preliminary conclusion is that acid-activated renin is a 'laboratory renin', which does not circulate in normal peripheral venous plasma.
 ...
PMID:Two forms of plasma renin after activation in vitro and their relation to natural plasma renin. 703 18


1 2 Next >>