Enzyme Immunoassay of the Active Metabolite (RS-5139) of Angiotensin Converting Enzyme Inhibitor (CS-622)

Abstract A simple and sensitive enzyme immunoassay (EIA) for determination of the active metabolite (RS-5139) of a new angiotensin converting enzyme inhibitor (CS-622) was developed. The N−succinimmidyl ester of RS-5139 was coupled with bovine serum albumin (BSA) and its conjugate was used as an immunogen. Horse radish peroxidase (HRP; EC 1, 11, 1, 7) was used as a labeled enzyme and 3, 3′, 5, 5′-tetramethylbenzidine was used as a substrate. The antiserum was used at a final dilution of 1:10000 and sensitivity was 10 pg in plasma and 20pg in urine. CS-622 exhibited cross-reactivity (22.3%), but other ACE inhibitors didn't exhibit cross-reactivity. The plasma levels determined by EIA and GC/MS was good agreement (y=6.58e-2+1.07x, Rˇ2=0.985, n–52).