Faster radioimmunoassay of angiotensin I at 37 degrees C.
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.
D000803:Angiotensin I / Q000032:analysis*; D000809:Angiotensins / Q000032:analysis*; D000937:Antigen-Antibody Reactions; D006801:Humans; D006973:Hypertension / Q000097:blood; D011863:Radioimmunoassay / Q000379:methods; D012083:Renin / Q000097:blood; D013696:Temperature; D013997:Time Factors
D000809:Angiotensins; D000803:Angiotensin I; D012083:Renin