Should blood samples for assay of plasma renin activity be chilled?

1978 ◽  
Vol 24 (11) ◽  
pp. 2042-2043 ◽  
Author(s):  
R L Emanuel ◽  
G H Williams
Keyword(s):  
Plasma Renin Activity ◽  
Room Temperature ◽  
Plasma Renin ◽  
The Other ◽  
Renin Activity ◽  
Angiotensin I ◽  
Blood Samples ◽  
Hypertensive Patients

Abstract Collecting blood on ice for renin determination reportedly may produce falsely high results. To assess the probability of this occurring under actual collection conditions, we measured renin activity in duplicate aliquots of plasma from blood samples from 25 hypertensive patients, both supine and upright, and in 10 supine normotensive controls. One aliquot of the blood was collected on ice and processed at 4 degrees C, the other at room temperature. The two aliquots showed no significant differences in renin activity. If anything, values for samples collected at room temperature were higher. Repeat determination on the same specimens stored at--20 degrees C for nine and 12 months revealed no significant changes in results for any samples, although the amount of angiotensin I found in the sample before incubation at 37 degrees C significantly increased. We conclude that it makes little difference at what temperature one collects blood for renin determination, but because of the wide fluctuations in "room" temperature we recommend that blood samples be collected on ice.

Effect of temperature on plasma renin samples.

1978 ◽  
Vol 24 (7) ◽  
pp. 1202-1204 ◽  
Author(s):  
F Fyhrquist ◽  
L Puutula
Keyword(s):  
Plasma Renin Activity ◽  
Room Temperature ◽  
Plasma Renin ◽  
Renin Activity ◽  
Effect Of Temperature ◽  
Plasma Samples ◽  
Hypertensive Patients ◽  
Variable Extent ◽  
Venous Plasma

Abstract Plasma renin activity was measured in parallel in Na2EDTA-contained plasma samples after storage at -20, 4, and 24 degrees C, and in the lyophilized state. In peripheral venous plasma from 22 hypertensive patients, the activity (range, 0.08-46.7 microgram/liter per hour) remained stable during three days of storage at 4 degrees C, but decreased to a variable extent when plasma was kept at 24 degrees C: in one day by 9.2%, two days by 25.6%, and three days by 74.0%. Values were the same for samples handled at room temperature and chilled to 4 degrees C within 3 h and parallel samples immediately cooled in an icebath and kept at 4 degrees C. Freezing (-20 degrees C) and thawing of plasma was associated with a 22% mean increase in activity (range, 0-83%). Lyophilization resulted in a smaller increase of plasma renin activity (mean 12%, range 0-46%). Blood for renin analysis need not be cooled immediately, but must be cooled to 4 degrees C within 2-3 h. It then is stabe for at least three days. Freezing or lyophilization appears to be associated with some cold activation of "prorenin."

scholarly journals Activity Assays and Immunoassays for Plasma Renin and Prorenin: Information Provided and Precautions Necessary for Accurate Measurement

2009 ◽  
Vol 55 (5) ◽  
pp. 867-877 ◽  
Author(s):  
Duncan J Campbell ◽  
Juerg Nussberger ◽  
Michael Stowasser ◽  
A H Jan Danser ◽  
Alberto Morganti ◽  
...  
Keyword(s):  
Plasma Renin Activity ◽  
Plasma Renin ◽  
Inhibitor Therapy ◽  
Renin Activity ◽  
Renin Inhibitor ◽  
Blood Samples ◽  
Hypertensive Patients ◽  
Active Renin ◽  
Open Conformation ◽  
Background Measurement

AbstractBackground: Measurement of plasma renin is important for the clinical assessment of hypertensive patients. The most common methods for measuring plasma renin are the plasma renin activity (PRA) assay and the renin immunoassay. The clinical application of renin inhibitor therapy has thrown into focus the differences in information provided by activity assays and immunoassays for renin and prorenin measurement and has drawn attention to the need for precautions to ensure their accurate measurement.Content: Renin activity assays and immunoassays provide related but different information. Whereas activity assays measure only active renin, immunoassays measure both active and inhibited renin. Particular care must be taken in the collection and processing of blood samples and in the performance of these assays to avoid errors in renin measurement. Both activity assays and immunoassays are susceptible to renin overestimation due to prorenin activation. In addition, activity assays performed with peptidase inhibitors may overestimate the degree of inhibition of PRA by renin inhibitor therapy. Moreover, immunoassays may overestimate the reactive increase in plasma renin concentration in response to renin inhibitor therapy, owing to the inhibitor promoting conversion of prorenin to an open conformation that is recognized by renin immunoassays.Conclusions: The successful application of renin assays to patient care requires that the clinician and the clinical chemist understand the information provided by these assays and of the precautions necessary to ensure their accuracy.

Faster radioimmunoassay of angiotensin I at 37 degrees C.

1978 ◽  
Vol 24 (1) ◽  
pp. 115-118 ◽  
Author(s):  
F Fyhrquist ◽  
L Puutula
Keyword(s):  
Plasma Renin Activity ◽  
Plasma Renin ◽  
Renin Activity ◽  
Plasma Samples ◽  
Angiotensin I ◽  
Hypertensive Patients ◽  
Standard Curve ◽  
Analytical Recovery ◽  
Nonequilibrium Conditions ◽  
Working Day

Abstract We applied a 1-h radioimmunoassay incubation at 37 degrees C in determining generated angiotensin I in an assay for plasma renin activity. Under these nonequilibrium conditions, 26% of the 125I-labeled angiotensin I was bound at zero dose of unlabeled angiotensin, as compared to 57% at equilibrium after 18 h at 4 degrees C. Sensitivity and useful range for the standard curve remained unchanged. Blanks were not altered. There was a good (r = .971) correlation between renin values in 120 plasma samples from hypertensive patients as measured with both procedures. With isoelectric focusing, we detected no damage to the labeled angiotensin I during incubation for 1 h at 37 degrees C in the presence of diluted plasma, disodium ethylenediaminetetraacetate, hydroxyquinoline, and neomycin. Analytical recovery of unlabeled angiotensin I added to the assay mixture was 98 +/- 2.3% (mean +/- SD). We conclude that our incubation conditions allow rapid and accurate assay of plasma renin activity to be completed in one working day.

Lack of angiotensin I accumulation after converting enzyme blockade by enalapril or lisinopril in man

1987 ◽  
Vol 72 (3) ◽  
pp. 387-389 ◽  
Author(s):  
J. Nussberger ◽  
D. B. Brunner ◽  
B. Waeber ◽  
J. Biollaz ◽  
Hans R. Brunner
Keyword(s):  
Angiotensin Ii ◽  
Plasma Renin Activity ◽  
Enzyme Inhibition ◽  
Venous Blood ◽  
Plasma Renin ◽  
Renin Activity ◽  
Converting Enzyme ◽  
Angiotensin I ◽  
Blood Samples ◽  
Converting Enzyme Inhibition

1. In nine normal volunteers, a series of five venous blood samples was obtained before and up to 24 h after converting enzyme inhibition by a single oral dose of enalapril or lisinopril. Plasma renin activity and blood angiotensin I were measured. 2. A close linear relationship was found between the increase in plasma renin activity and the increase in blood angiotensin I. 3. The linear correlation between plasma renin activity and blood angiotensin I remained after converting enzyme inhibition. 4. Thus, the rise in angiotensin I after inhibition of the conversion of angiotensin I to angiotensin II is due to an enhanced release of renin rather than to accumulation of angiotensin I.

Effect of enalapril (MK-421), an orally active angiotensin I converting enzyme inhibitor, on blood pressure, active and inactive plasma renin, urinary prostaglandin E2, and kallikrein excretion in conscious rats

1984 ◽  
Vol 62 (1) ◽  
pp. 116-123 ◽  
Author(s):  
Ernesto L. Schiffrin ◽  
Jolanta Gutkowska ◽  
Gaétan Thibault ◽  
Jacques Genest
Keyword(s):  
Blood Pressure ◽  
Angiotensin Ii ◽  
Plasma Renin Activity ◽  
Plasma Renin ◽  
Ace Inhibition ◽  
Renin Activity ◽  
Prostaglandin E ◽  
Converting Enzyme ◽  
Angiotensin I ◽  
Angiotensin I Converting Enzyme

The angiotensin I converting enzyme (ACE) inhibitor enalapril (MK-421), at a dose of 1 mg/kg or more by gavage twice daily, effectively inhibited the pressor response to angiotensin I for more than 12 h and less than 24 h. Plasma renin activity (PRA) did not change after 2 or 4 days of treatment at 1 mg/kg twice daily despite effective ACE inhibition, whereas it rose significantly at 10 mg/kg twice daily. Blood pressure fell significantly and heart rate increased in rats treated with 10 mg/kg of enalapril twice daily, a response which was abolished by concomitant angiotensin II infusion. However, infusion of angiotensin II did not prevent the rise in plasma renin. Enalapril treatment did not change urinary immunorcactive prostaglandin E2 (PGE2) excretion and indomethacin did not modify plasma renin activity of enalapril-treated rats. Propranolol significantly reduced the rise in plasma renin in rats receiving enalapril. None of these findings could be explained by changes in the ratio of active and inactive renin. Water diuresis, without natriuresis and with a decrease in potassium urinary excretion, occurred with the higher dose of enalapril. Enalapril did not potentiate the elevation of PRA in two-kidney one-clip Goldblatt hypertensive rats. In conclusion, enalapril produced renin secretion, which was in part β-adrenergically mediated. The negative short feedback loop of angiotensin II and prostaglandins did not appear to be involved. A vasodilator effect, apparently independent of ACE inhibition, was found in intact conscious sodium-replete rats.

Effect of ovariectomy on vasopressin, ACTH, and renin activity responses to hypotension

1991 ◽  
Vol 261 (1) ◽  
pp. R223-R230 ◽  
Author(s):  
M. Keller-Wood ◽  
C. E. Wood
Keyword(s):  
Plasma Renin Activity ◽  
Arginine Vasopressin ◽  
Adrenocorticotropic Hormone ◽  
Plasma Renin ◽  
Renin Activity ◽  
Plasma Acth ◽  
Blood Samples

The gonadal axis is thought to modulate adrenocorticotropic hormone (ACTH), arginine vasopressin (AVP), and plasma renin activity (PRA) responses to stimuli in several species. These experiments were designed to compare the responses to hypotension in chronically ovariectomized ewes and intact ewes. The ewes were infused with nitroprusside at rates of 5, 10, or 15 micrograms.kg-1.min-1 or infused with vehicle for 10 min. The response to 15 micrograms.kg-1.min-1 was also tested with or without treatment with 10 mg of dexamethasone 2 h before nitroprusside. Blood samples were collected before and at 5, 10, 15, 20, and 30 min after the start of the infusion for measurement of plasma ACTH, AVP, and PRA. In both groups of animals there were significant responses to hypotension. There was a significant effect of ovariectomy on ACTH, AVP, and PRA responses. ACTH and PRA responses were lower in the ovariectomized ewes; AVP responses were increased in the ovariectomized ewes. Administration of dexamethasone inhibited ACTH responses and did not inhibit PRA responses in both groups of ewes. Administration of dexamethasone did not inhibit the AVP response in the intact ewes but did reduce the response in the ovariectomized ewes.

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

1973 ◽  
Vol 45 (s1) ◽  
pp. 295s-299s ◽  
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.

Measurement of Plasma Renin Activity as a Valid Estimation of Plasma Angiotensin Status

1978 ◽  
Vol 15 (1-6) ◽  
pp. 250-252 ◽  
Author(s):  
J. E. Roulston ◽  
G. A. Macgregor ◽  
Theresa Adam ◽  
Nirmala D. Markandu
Keyword(s):  
Angiotensin Ii ◽  
Plasma Renin Activity ◽  
Plasma Renin ◽  
Renin Activity ◽  
Activity Measurement ◽  
Plasma Samples ◽  
Angiotensin I ◽  
Plasma Angiotensin ◽  
Rate Limiting

Measurement of plasma renin activity is widely used as an indirect assessment of plasma angiotensin II concentration. There has been some controversy over the validity of this assay as an estimate of circulating angiotensin II levels because, during the in vitro generation of angiotensin I by renin, over a period of time, substrate concentration may diminish to such an extent that it becomes rate-limiting, giving an artificially low reflection of angiotensin II levels. In this paper the initial angiotensin I concentration, that is the concentration before in vitro angiotensin I generation, has been compared with the corresponding plasma renin activity for 2752 individual plasma samples. A linear relationship was found between the initial angiotensin I concentration and the plasma renin activity below 60 ng ml−1 h−1. This indicates that, under the conditions of this assay, substrate does not appear to become rate-limiting except at exceedingly high levels of plasma renin activity. These results appear to provide further validation for the use of plasma renin activity measurement as a reflection of the concentration of circulating angiotensin II levels.

Cryoactivation of renin in plasma from pregnant and nonpregnant subjects, and its control.

1979 ◽  
Vol 25 (11) ◽  
pp. 1972-1974 ◽  
Author(s):  
J Rowe ◽  
E D Gallery ◽  
A Z Györy
Keyword(s):  
Plasma Renin Activity ◽  
Pregnant Women ◽  
Room Temperature ◽  
Plasma Renin ◽  
Renin Activity ◽  
Baseline Values

Abstract Plasma renin activity increased by a mean of 7% from baseline values when blood from nonpregnant persons was kept at 0 degrees C for 5 h before incubation. Freezing chilled plasma and thawing it before incubation resulted in a mean increase of 11%. The same procedures used on plasma from normal pregnant women produced mean increases in plasma renin activity of 44 and 89%, respectively. If blood from pregnant women was kept at 0 degrees C for 5 h, and the plasma then separated, frozen, and thawed before incubation, the resulting mean increase in plasma renin activity from baseline values was 160%. We conclude that plasma from pregnant women should be handled at room temperature, or, if samples must be stored, they must be rapidly frozen, then thawed as rapidly as possible before incubation and assay if results are to be reproducible.

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