title: Determination of ISF-2405, an active metabolite of cadralazine, in plasma and tissues by radioimmunoassay.
abstract: A radioimmunoassay has been developed which makes possible sensitive and specific determination of an active metabolite of cadralazine, (+/-)-6-[ethyl(2-hydroxypropyl)amino]-3-hydrazinopyridazine (ISF-2405), in plasma and tissues. On account of its lability in a sample solution, ISF-2405 in biological samples was selectively derivatized to a stable form, (+/-)-6-[ethyl(2-hydroxypropyl)amino]-3-(3,5-dimethyl-1-pyrazolyl) pyridazine (ISF-3349), by treatment with acetylacetone. The concentration of ISF-2405 was determined by the assay of the resultant ISF-3349. Antiserum against ISF-3349 was elicited in guinea pigs immunized with the ISF-3349 derivative coupled with bovine serum albumin. The obtained antiserum was highly specific for ISF-3349, and did not cross-react with either cadralazine or its metabolites. [Pyrazole-4-3H]labeled ISF-3349 with a specific activity of 13.9 Ci/mmol was used as the radioligand. Assays of ISF-2405 in plasma and tissues were possible over the concentration range from 0.4 to 6.4 ng/ml with 1 ml of plasma, and from 2 to 64 ng/g with 100 mg of tissue. Plasma and blood vessel levels of ISF-2405 in rats after single oral administration of cadralazine have also been determined by the present method.
authors.affiliation: Research Laboratories, Dainippon Pharmaceutical Co., Ltd., Osaka, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Terauchi
authors.forename: S
authors.initials: S
authors.lastname: Watari
authors.forename: S
authors.initials: S
authors.lastname: Ishikawa
authors.forename: M
authors.initials: M
authors.lastname: Nakao
authors.forename: T
authors.initials: T
authors.lastname: Negoro
authors.forename: A
authors.initials: A
authors.lastname: Kagemoto
authors.forename: Y
authors.initials: Y
authors.lastname: Sekine
authors.forename: M
authors.initials: M
authors.lastname: Hashimoto
mesh_terms: D000818:Animals; D000906:Antibodies / Q000032:analysis / Q000276:immunology; D001011:Aorta / Q000032:analysis; D006168:Guinea Pigs; D008297:Male; D011724:Pyridazines / Q000032:analysis* / Q000097:blood / Q000276:immunology / Q000378:metabolism*; D011863:Radioimmunoassay; D051381:Rats; D011919:Rats, Inbred Strains; D013997:Time Factors; D014018:Tissue Distribution
chemical_list: D000906:Antibodies; D011724:Pyridazines; C056192:ISF 3349; C055809:ISF 2405; C031877:cadralazine