Estimation of serum protein binding of compounds metabolized in serum using matrix inhibition.
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.
Uchimura
Takahide
T
Fuji Gotemba Research Laboratories, Chugai Pharmaceutical Co Ltd, Gotemba, Shizuoka, Japan. uchimuratkh@chugai-pharm.co.jp <uchimuratkh@chugai-pharm.co.jp>
Kato
Motohiro
M
Shiokawa
Rie
R
Nabuchi
Yoshiaki
Y
Saito
Kimitoshi
K
Kinoshita
Haruki
H
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
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