title: Estimation of serum protein binding of compounds metabolized in serum using matrix inhibition.
abstract: It is difficult to evaluate the serum protein binding of compounds that are metabolized in rat serum, even when using ultrafiltration. Protein binding was estimated using matrix inhibition, a method that uses the change in metabolic velocity achieved by changing the free fraction of a compound in the incubation mixture by diluting the serum with phosphate buffered saline. The T(1/2) of phenyl nicotinate, benzyl nicotinate, octyl nicotinate, hexyl nicotinate, butyl nicotinate and [(3)H] compound A were 0.165, 0.780, 2.62, 3.94, 5.22 and 135 min, respectively, with protein binding values of 82.1%, 91.6%, 98.8%, 98.5%, 85.5% and 96.9%. The protein binding value of compound A estimated by ultrafiltration was 93.4%, indicating that the two methods give similar values. The matrix inhibition method is thus applicable for the evaluation of compounds metabolized in serum, and provides a simple, useful method to determine protein binding.
authors.affiliation: Fuji Gotemba Research Laboratories, Chugai Pharmaceutical Co Ltd, Gotemba, Shizuoka, Japan. uchimuratkh@chugai-pharm.co.jp <uchimuratkh@chugai-pharm.co.jp>
authors.forename: Takahide
authors.initials: T
authors.lastname: Uchimura
authors.forename: Motohiro
authors.initials: M
authors.lastname: Kato
authors.forename: Rie
authors.initials: R
authors.lastname: Shiokawa
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Nabuchi
authors.forename: Kimitoshi
authors.initials: K
authors.lastname: Saito
authors.forename: Haruki
authors.initials: H
authors.lastname: Kinoshita
mesh_terms: D000818:Animals; D001798:Blood Proteins / Q000378:metabolism*; D004952:Esters; D066298:In Vitro Techniques; D009539:Nicotinic Acids / Q000097:blood*; D011485:Protein Binding; D051381:Rats; D044967:Serum
chemical_list: D001798:Blood Proteins; D004952:Esters; D009539:Nicotinic Acids; C533214:octyl nicotinate; C049457:hexyl nicotinate; C029162:butyl nicotinate; C025653:nicotinic acid benzyl ester; C533213:phenyl nicotinate