Angiotensins I and II, active and inactive renin, renin substrate, renin activity, and angiotensinase in human liquor amnii and plasma

Although heparin was reported in the 1960s to inhibit renin activity, this has not always been confirmed by other investigators. Hence, we re-examined whether heparin really inhibits renin or not. Renin activities were determined by radioimmunoassay of angiotensin I generated at pH 7.4. (i) No significant difference was found between the two kinds of plasma samples obtained with heparin and with EDTA as anticoagulant, in ARC (renin activity with addition of sheep renin substrate), TRC (ARC after activation of inactive renin by trypsin), or PRA (plasma renin activity without additional substrate), (ii) Even in higher concentrations of heparin up to 500 U/mL, neither PRA, ARC, nor TRC of plasma was affected significantly. (iii) Heparin, in concentrations up to 500 U/mL, exerted no significant effect on TRC of the media of human vascular smooth muscle cell culture. In conclusion, heparin does not exert any significant inhibitory effect on human renin nor does it affect activation of inactive renin by trypsin in the range of concentration of practical use, under the conditions employed in this study.Key words: plasma renin, tissue renin, inactive renin, vascular smooth muscle cell, trypsin.

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Enzymatic Activity of Renin in Plasma of Normal and Uraemic Subjects

Clinical Science ◽

10.1042/cs0670365 ◽

1984 ◽

Vol 67 (3) ◽

pp. 365-368 ◽

Cited By ~ 3

Author(s):

Theodore A. Kotchen ◽

Tam T. Guyenne ◽

Pierre Corvol ◽

Joel Menard

Keyword(s):

Renal Failure ◽

Enzymatic Activity ◽

Plasma Renin ◽

Normal Subjects ◽

Renin Activity ◽

Angiotensin I ◽

Renin Substrate ◽

Inactive Renin ◽

Substrate Concentrations

1. Plasma renin reactivity (PRR) is the rate of angiotensin I production after addition of renin to plasma, minus endogenous renin activity. PRR is increased in plasma of patients with renal failure compared with that of normal subjects. The present study was carried out to determine if increased PRR in uraemic plasma is related to differences of endogenous active or inactive renin, endogenous renin substrate, or pH of the incubation in vitro. 2. PRR in plasma of ten uraemic patients was greater (P<0.02) than that in plasma of ten normal subjects in incubations carried out at pH 7.4 and 5.7. 3. Increased PRR was not accounted for by differences of endogenous active and inactive renin activity. 4. After addition of renin, renin concentration (measured by direct radioimmunoassay) did not differ in normal and uraemic plasma. 5. Renin substrate concentration, measured both indirectly and by direct radioimmunoassay, also did not differ in normal and uraemic plasma. 6. Increased PRR in uraemic plasma is not related to alterations of renin or renin substrate concentrations. These observations are consistent with our earlier hypothesis that there is a deficiency of a renin inhibitor in uraemic plasma.

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Trypsin-Activatable Inactive Renin in Rat Plasma

Clinical Science ◽

10.1042/cs0640137 ◽

1983 ◽

Vol 64 (2) ◽

pp. 137-140 ◽

Cited By ~ 14

Author(s):

Nicola Glorioso ◽

Paolo Madeddu ◽

Paolo Dessi'-Fulgheri ◽

Giuseppe Fois ◽

Franca Meloni ◽

...

Keyword(s):

Rat Plasma ◽

Renin Activity ◽

Trypsin Activity ◽

Ph Optimum ◽

Renin Substrate ◽

Inactive Form ◽

Wide Range ◽

Maximal Activation ◽

Inactive Renin ◽

Range Of Variation

1. Activation of inactive renin in rat plasma has been studied with different trypsin concentrations and incubation times at pH 6.2 and 4°C. 2. Trypsin concentrations below 2 mg/ml, lower than endogenous rat plasma anti-trypsin activity, do not activate inactive renin, whereas maximal activation is obtained with trypsin at 6 mg/ml for 1 min at 4°C, pH 6.2. 3. Under these conditions trypsin can cleave dialysable fragments from renin substrate. ANG I can be generated at 37°C with a pH optimum of 5.3. Nevertheless, the ANG I formation at pH 6.2 was totally unaffected. 4. Incubations longer than 2 min with trypsin at 6 mg/ml can induce a direct cleavage of dialysable ANG I-containing fragments strongly interfering with the measurements of renin activity at pH 6.2. 5. On average 40% of the total renin measured in plasma of normotensive WK rats is in the inactive form, although a wide range of variation is observed.

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Measurement of inactive renin in normal, nephrectomized, and adrenalectomized rats

Canadian Journal of Physiology and Pharmacology ◽

10.1139/y91-205 ◽

1991 ◽

Vol 69 (9) ◽

pp. 1381-1384 ◽

Cited By ~ 4

Author(s):

Knud Poulsen ◽

Arne Høj Nielsen ◽

Arne Johannessen

Keyword(s):

Animal Model ◽

Exchange Resin ◽

Cation Exchange Resin ◽

Plasma Renin ◽

Rat Plasma ◽

Angiotensin I ◽

Renin Substrate ◽

Suitable Animal Model ◽

Inactive Renin ◽

Adrenalectomized Rats

In a new method for measurement of inactive rat plasma renin, the trypsin generated angiotensin I immunoreactive material, which was HPLC characterized as similar to tetradecapeptide renin substrate, is removed by a cation exchange resin before the renin incubation step. The method also corrects for trypsin destruction of endogenous angiotensinogen by the addition of exogenous angiotensinogen. When measured with this method inactive renin in rat plasma decreased after nephrectomy and increased after adrenalectomy. This is in accordance with findings in humans. A sexual dimorphism of prorenin (inactive renin) in rat plasma, similar to that reported in humans and mice, was demonstrated. Thus, inactive renin in the rat is no exception among species, and the rat might be a suitable animal model for further studies dealing with the physiology of prorenin in plasma and tissues.Key words: angiotensinogen, inactive renin, renin.

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Plasma renin activity and plasma prorenin assays

Clinical Chemistry ◽

10.1093/clinchem/37.10.1811 ◽

1991 ◽

Vol 37 (10) ◽

pp. 1811-1819 ◽

Cited By ~ 139

Author(s):

J E Sealey

Keyword(s):

Plasma Renin Activity ◽

Sodium Intake ◽

Vascular Complications ◽

Plasma Renin ◽

Renin Activity ◽

Blood Collection ◽

Kinetic Assay ◽

Renin Substrate ◽

Patients With Diabetes ◽

Commercial Kits

Abstract Sensitivity and accuracy are essential features of an assay of plasma renin activity (PRA) because the normal concentration of PRA is only 1 pmol/L, and subnormal concentrations have diagnostic relevance. Conditions for blood collection need to be standardized but the conditions are not difficult for outpatients. For routine diagnostic purposes blood should be collected from ambulatory (ideally, untreated) patients on moderate sodium intake. To avoid irreversible cryoactivation of plasma prorenin (which is present in 10-fold greater concentrations than renin), samples should be processed at room temperature and stored completely frozen. Cryoactivation occurs when plasma is liquid at temperatures less than 6 degrees C. PRA is commonly measured with an enzyme kinetic assay in which angiotensin I (Ang I) is formed by the reaction of plasma renin with endogenous renin substrate (angiotensinogen). The Ang I so formed is measured by RIA; results are expressed as an hourly rate (micrograms/L formed per hour). This method, which is provided by most commercial kits, has the potential for unlimited sensitivity because the step for Ang I generation can be prolonged as long as necessary, so that enough Ang I forms to be measured accurately. Unfortunately, that sensitivity is not always exploited. Dilution of plasma during pH adjustment should be kept to a minimum. The Ang I generation step should last at least 3 h. The step should last 18 h for samples with PRA less than 1.0 micrograms/L per hour, to eliminate the errors inherent in the measurement and subtraction of immunoreactive Ang I in the untreated plasma (blank subtraction). These changes actually simplify PRA measurements because they eliminate the need for ice in the clinic and reduce by almost half the number of samples to be assayed by RIA. I also describe the method for measurement of plasma prorenin, which may be an important marker for patients with diabetes mellitus who subsequently develop vascular complications.

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Plasma Renin Activity and Plasma Renin Substrate in Hypertension Associated with Steroid Excess

Clinical Science ◽

10.1042/cs045295s ◽

1973 ◽

Vol 45 (s1) ◽

pp. 295s-299s ◽

Cited By ~ 3

Author(s):

L. R. Krakoff ◽

M. Mendlowitz

Keyword(s):

Oral Contraceptive ◽

Plasma Renin Activity ◽

Cushing’S Syndrome ◽

Plasma Renin ◽

Cushing's Syndrome ◽

Glucocorticoid Therapy ◽

Renin Activity ◽

Angiotensin I ◽

Renin Substrate ◽

Contraceptive Agents

1. Plasma renin activity and plasma renin substrate were measured by radioimmunoassay of generated angiotensin I in patients with steroid excess syndromes. Significant increases in substrate were observed in patients with Cushing's syndrome, during glucocorticoid therapy and on oral contraceptive agents. Suppression of plasma renin activity occurred only in primary aldosteronism. 2. The Michaelis constant (Km) for the reaction between renin and substrate in plasma at physiological pH (7.4) was also determined. The extent to which elevated plasma renin substrate increases the velocity of angiotensin I formation was then calculated. 3. In patients with Cushing's syndrome, glucocorticoid therapy or oral contraceptive use, elevated renin substrate coupled with failure of suppression of circulating renin results in increased angiotensin I formation.

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Effect of Acid, Trypsin and Cold Treatment and of Renin— Plasma Interaction on the Activity of Renin Secreted by Rat Kidney

Clinical Science ◽

10.1042/cs0570233 ◽

1979 ◽

Vol 57 (3) ◽

pp. 233-240 ◽

Cited By ~ 9

Author(s):

H. Nakane ◽

Y. Nakane ◽

P. Corvol ◽

J. Menard

Keyword(s):

Rat Kidney ◽

Cold Treatment ◽

Rat Plasma ◽

Renin Activity ◽

Trypsin Treatment ◽

Plasma Interaction ◽

Isolated Perfused Rat Kidney ◽

Perfused Rat Kidney ◽

Inactive Renin ◽

The Difference

1. Renin release from the isolated perfused rat kidney was markedly stimulated by isoprenaline or anoxia. Renin secreted into the blood-free perfusate was not activated by exposure to cold or dialysis to pH 3·3, suggesting the absence either of cryo- or acid-activatable renin or of factors necessary to activate inactive renin. 2. Trypsin treatment did not change renin concentration in the perfusate samples. 3. When binephrectomized rat plasma was added to perfusate samples before dialysis, renin concentration in the acidified samples was significantly higher than in samples dialysed to pH 6·5. Diminished renin recovery in the latter samples caused this difference. Binephrectomized rat plasma itself had no significant renin activity before or after acid dialysis, indicating the absence of any important extrarenal source of active or acid-activatable renin in rats. 4. Acidification of binephrectomized rat plasma before its addition to the perfusate samples markedly reduced the difference between renin recovery during dialysis to pH 3·3 and dialysis to pH 6·5, indicating that acidification irreversibly inhibited renin inactivation by binephrectomized rat plasma. No net increase in renin concentration was observed in any of our experiments. 5. These results suggest that rat kidney does not secrete inactive renin. They also point to the existence of renin inactivation by rat plasma at neutral pH, which might lead to overestimation of acid-activatable renin in rats.

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Plasma Renin Activity, Active and Inactive Renin Concentrations, and their Responses to β1-Adrenoceptor Blockade with Metoprolol in Hyperthyroidism

Hormone and Metabolic Research ◽

10.1055/s-2007-1012391 ◽

1986 ◽

Vol 18 (09) ◽

pp. 630-634 ◽

Cited By ~ 3

Author(s):

T. Baba ◽

S. Murabayashi ◽

K. Aoyagi ◽

M. Kitaoka ◽

M. Nakazono ◽

...

Keyword(s):

Plasma Renin Activity ◽

Plasma Renin ◽

Renin Activity ◽

Inactive Renin

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Renin response and angiotensinogen control during graded hemorrhage and shock in the dog

American Journal of Physiology-Legacy Content ◽

10.1152/ajplegacy.1976.231.4.1300 ◽

1976 ◽

Vol 231 (4) ◽

pp. 1300-1307 ◽

Cited By ~ 11

Author(s):

O Beaty ◽

CH Sloop ◽

Schmid HE ◽

Buckalew VM

Keyword(s):

Blood Pressure ◽

Angiotensin Ii ◽

Plasma Renin ◽

Renin Activity ◽

Elevated Plasma ◽

Renin Substrate ◽

Hemorrhagic Hypotension ◽

Shock Phase ◽

Circulatory Stress ◽

The Relationship

Hemorrhage and hemorrhagic hypotension have been shown to be potent stimulators of renin release. However, the relationship between angiotensinogen consumption and angiotensinogen production has yet to be completely defined during this type of circulatory stress. Peripheral renin activity increased progressively as the blood pressure was decreased stepwise by hemorrhage to 50 mmHg and remained elevated throughout the shock phase of the experiment. Angiotensinogen did not change from control (809 ng/ml) throughout hemorrhabic hypotension and shock. During hemorrhagic hypotension, with the infusion of the angiotensin antagonist, [1-sarcosine, 8-alanine]angiotensin II, angiotensinogen concentration fell progressively from 693 to 208 ng/ml at 50 mmHg. Intravenous angiotensin II infused continuously after the mean blood pressure reached 50 mmHg significantly elevated plasma angiotensinogen concentration. In conclusion, during hemorrhagic hypotension and shock, the kidney and the liver appeared capable of maintaining elevated plasma renin activity and adequate plasma renin substrate, angiotensinogen, respectively. The mechanism responsible for the maintenance of plasma angiotensinogen is suggested to involve a positive-feedback effect of angiotensin II on the liver.

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