Biol. Pharm. Bull.

Biol. Pharm. Bull., 24(9),1037-1043, September 2001

Regular Articles

Application of the PKCYP-test in Cases of Altered CYP1A2 for Multiple CYP Systems in Rat Models of Disease

Noriko MATSUNAGA,^a Kenji HATTORI,^a Hisashi IIZASA,^a Junko KIZU,^b Akira TAKANAKA,^c and Emi NAKASHIMA^*,a

Department of Pharmaceutics,^a and Practical Pharmacy,^b Kyoritsu College of Pharmacy, 1–5–30 Shiba-koen, Minato-ku, Tokyo 105–8512, Japan, and The Organization for Pharmaceutical Safety and Research,^c 3–3–2 Kasumigaseki, Chiyoda-ku, Tokyo 100–0013, Japan.

Previously, we established a method to assess drug metabolism capacity based on a pharmacokinetic estimation of the quantity of cytochrome P450 (CYP) in vivo (PKCYP-test) by introducing an apparent liver-to-blood free concentration gradient in vivo (qg). The qg values were determined as the ratio of in vivo–in vitro clearance. In this study, we examined the application of the PKCYP-test to the clearance of acetanilide and caffeine mediated by CYP1A2 using rat models in which the levels of CYP enzymes were reduced. Rats fed a choline-deficient diet (CD-fed) and aged rats were used as models for a low level of CYP in the liver. In both rat models, the contribution (f_CYP) of CYP1A2 to the in vivo intrinsic clearance values (CL_int) of acetanilide and caffeine metabolism was less than unity, suggesting that other metabolic pathways are involved in the CL_int. The in vivo clearance for CYP1A2 was estimated by multiplying f_CYP by CL_int, then the value of qg was determined as the ratio of in vivo–in vitro clearance. We predicted the level of CYP1A2 in CD-fed and aged rats, based on the clearance of acetanilide mediated by CYP1A2, using the qg value of control rats. The clearance of caffeine mediated by CYP1A2 in CDfed and aged rats, as estimated from the predicted level of CYP1A2, correlated with the observed values.
In conclusion, we have demonstrated that the PKCYP-test can be applied to CYP1A2 for drugs metabolized by multiple CYP isozymes, and/or to models involving reduced CYP.

Key words PKCYP-test; probe; CYP1A2; choline-deficient; aged

Regular Articles

Application of the PKCYP-test in Cases of Altered CYP1A2 for Multiple CYP Systems in Rat Models of Disease

Noriko MATSUNAGA,a Kenji HATTORI,a Hisashi IIZASA,a Junko KIZU,b Akira TAKANAKA,c and Emi NAKASHIMA*,a

Department of Pharmaceutics,a and Practical Pharmacy,b Kyoritsu College of Pharmacy, 1–5–30 Shiba-koen, Minato-ku, Tokyo 105–8512, Japan, and The Organization for Pharmaceutical Safety and Research,c 3–3–2 Kasumigaseki, Chiyoda-ku, Tokyo 100–0013, Japan.

Noriko MATSUNAGA,^a Kenji HATTORI,^a Hisashi IIZASA,^a Junko KIZU,^b Akira TAKANAKA,^c and Emi NAKASHIMA^*,a

Department of Pharmaceutics,^a and Practical Pharmacy,^b Kyoritsu College of Pharmacy, 1–5–30 Shiba-koen, Minato-ku, Tokyo 105–8512, Japan, and The Organization for Pharmaceutical Safety and Research,^c 3–3–2 Kasumigaseki, Chiyoda-ku, Tokyo 100–0013, Japan.