RADIOIMMUNOASSAY FOR AN ANTISCHISTOSOMAL DRUG, 4-NITRO-4'-ISOTHIOCYANO-DIPHENYLAMINE (7505)

A radioimmunoassay methed for an anti-schistosomal drug, 4-nitro-4'-isothiocyano-diphenylamine, is described.The antigen used for immunizing rabbits was prepared by coupling 7505 with ovalbumin or porcine IgG. ~(131)I was used for the preparation of labelled antigen, polyethylene glycol (PEG)being used as a separating agent.This assay comprises a range of about 0.64-400 ng 7505 per test. The reproducibility was shown to be satisfactory. The results obtained from PEG separation was close to those from double antibody method.After giving 7505 (120 mg/kg body wt.) per os to four rabbits, the blood concentration of 7505 varies in a similar pattern. The levels rose to a peak value about 2～3 days after drug administration. The results obtained were the same as those by the method using ³H-7505. A series of 14 analogs of 7505 have been tested by RIA for cross reactions, and the relationships between the degree of cross reactions and Validity of experimental treatments were discussed.It is concluded that cross reactions existed in those compounds comprising the structure of NO₂ R. If the—group between the two benzene rings was modified, the cross reactions vanished. 7505 antisera may also be used in the quantitative determination for some of the anlogs of 7505 tested.