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

Plasma renin activity is quantitated by measuring the rate of angiotensin generation during incubation of plasma renin with endogenous renin substrate. The angiotensin is quantitated by radioimmunoassay. Our studies indicate that the incubation step is best carried out in undiluted plasma at the pH optimum for renin (pH 5.7) in the presence of EDTA, neomycin, and DFP or PMSF. By using these conditions, incubation of low-renin samples can be prolonged for up to 18 hr, because angiotensinases and converting enzyme are completely inhibited. Accuracy is enhanced by prolongation of the incubation time, which results in more angiotensin and eliminates the need for blank subtraction. Incubation at pH 7.4 is disadvantageous because of lower rates of generation of angiotensin 1, because of the inability to maintain pH constant without addition of strong buffer, and because the incubation step cannot be prolonged beyond 3 hr. Dilution of plasma is undesirable because it results in a slower reaction rate due to dilution of both enzyme and substrate, and it is not possible to correct for the effect of substrate dilution. The radioimmunoassay of angiotensin I presents few unusual problems. The volume of plasma assayed should be 20 muI or less. If blank subtraction is used, antibodies should be screened to determine the extent to which they bind nonspecific substances in plasma, and then to ascertain whether the blank is entirely additive when angiotensin is added to it. Assay sensitivity is an important issue, since approximately 30 percent of patients with essential hypertension have subnormal plasma renin activity. In a study of three different commercial kits we found that many low-renin samples were undetectable and major fractions could not be discriminated with precision or consistency from normal renin samples. However, the incubation conditions can be easily modified, so that an 18-hr incubation can be utilized and then low-renin samples can be detected with the same degree of accuracy as those with normal plasma renin activity.
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PMID:Radioimmunoassay of plasma renin activity. 16 97

The main application of the radioimmunoassay for angiotensin I is the measurement of plasma renin activity (PRA). Methods published for the measurement of PRA differ in many details and make the comparison of results difficult. This paper deals with some of the problems. 1. The radioactive labelling of angiotensin I using chloramine-T requires the purification of the labelled peptide. A method applying both anion exchange chromatography and gel filtration is described. It resulted in tracer angiotensins of very reproducible characteristics. 2. For the measurement of PRA, the pH of the plasma has to be adjusted prior to the incubation. The adjustment to the physiologic pH of 7.4 is recommended. 0.1 volume of a concentrated buffer controlled the pH during a three hours incubation without diluting the plasma too much. 3. At pH 7.4, EDTA, dimercaprol, and 8-hydroxyquinoline were found to inhibit converting enzyme and angiotensinases better than EDTA and DFP and should therefore be used as inhibiting agents. 4. Nonspecific cross reaction of antisera are the cause of the blank values when angiotensin I is measured in unextracted plasma. The problem of subtraction of a blank may be minimized by the selection of an antiserum of high specificity which shows no or only little nonspecific cross reaction. Lor or unmeasurable blank values will result.
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PMID:Problems connected with plasma renin activity measurements by angiotensin I radioimmunoassay. 23 5

Previous studies have indicated the existence of an unknown AII-forming enzyme (AFE) in the glomerular region. This investigation was undertaken to characterize this enzyme further and to elucidate its possible physiologic role. AFE activity was found in cortical tissue and in microdissected superficial and juxtamedullary glomeruli but not in renal medulla. It could be blocked by the converting enzyme (CE) inhibitors SQ 20881 (133.5 micrograms/ml; 70%), SQ 14225 (20 ng/ml; 80%), and DFP (20 micrograms/ml; 80%). In contrast to AI CE, AFE was neither blocked by EDTA nor stimulated by sodium chloride. In a further study, AFE activity and AII immunoreactivity were measured simultaneously in different renal structures and in plasma under control conditions and following water deprivation. Highest AII immunoreactivity was demonstrated in microdissected glomeruli (about 10 ng/g; N = 11) and lower amounts in cortical tissue (2.83 +/- 0.72 ng/g; N = 12), avascular cortical tissue (1.80 +/- 1.08 ng/g; N = 3), outer medulla (1.52 +/- 0.33 ng/g; N = 12), inner medulla (0.72 +/- 0.17 ng/g; N = 2), and in plasma (0.212 +/- 0.066 ng/ml; N = 12). Water deprivation had no measurable effect on AFE activity; but AII immunoreactivity increased significantly in all samples. This indicates that, in spite of the extremely high juxtaglomerular renin activity, AFE cannot be regarded as the limiting enzyme for local AII formation under the conditions investigated.
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PMID:Juxtaglomerular angiotensin II formation. 618 38

A monolayer cell culture of juxtaglomerular cells (JGC) was derived from the renal cortex of neonatal rats. The JGC had the characteristics of those within the kidney, including peripheral dense bodies and myofibrils indicating a smooth muscle origin; rough ER containing fluffy material consistent with protein synthesis; a prominent Golgi apparatus for packaging granules, and granules having the characteristics of secretory granules and lysosomes. Transplants of the cultured cells into syngeneic recipients survived for 2 weeks or longer and retained the features of JGC. The JGC granules fluoresced when treated with a rabbit antibody against pure rat renin, followed by fluorescein isothyocyanate conjugated F(ab')2 fragment of goat antirabbit IgG (Fc fragment) heavy chain specific. The latter indicated the presence of renin. The JGC were lysed in the presence of DFP, captopril, leupeptin, and EDTA, and were extracted in the presence of pepstatin. The lysate contained renin activity that was inhibited by a specific renin antibody. Nonspecific proteases were excluded by the antibody and its pH optimum. Angiotensin I-converting enzyme was detected in the lysate prepared without the use of EDTA and captopril. Angiotensins I and II/III were derived from the extract by additional extractions, TLC, and RIA, using highly specific antibodies. The angiotensins were confirmed by chromatography monitored by authentic angiotensins. We concluded that the cultured JGC contained renin, angiotensin I-converting enzyme, and angiotensin I and II/III.
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PMID:Juxtaglomerular cells grown as monolayer cell culture contain renin, angiotensin I-converting enzyme, and angiotensin I and II/III. 628 94