Pharmacokinetic properties of newly synthesized retinoid X receptor agonists possessing a 6-[N-ethyl-N-(3-alkoxy-4-isopropylphenyl)amino]nicotinic acid skeleton in rats

Acute Peripheral Inflammation Increases Plasma Concentration of Hypoglycemic Agent Nateglinide with Decreased Hepatic Drug-Metabolizing Activity in Rats

The effects of inflammation on hypoglycemic agents were evaluated in male rats with acute peripheral inflammation (API). Nateglinide (NTG) was utilized as a model compound, since it is a hepatically-metabolized compound and its metabolism is mainly mediated by CYP 2C11 enzyme. In the experiments, rats were subjected to carrageenan injection into their hind paws for API induction, and the plasma concentration profiles of NTG were then examined. In addition, pooled liver microsomes were prepared from control and API rats, and the hepatic drug-metabolizing activity toward NTG and the hepatic expression of CYP2C11 protein were evaluated. It was shown that the plasma concentration of NTG following its intravenous administration decreases at a slower rate in API rats than that in control rats. It was also indicated in the incubation study with the liver microsomes that the hepatic drug-metabolizing activity toward NTG decreases in API rats. Additionally, it was revealed in Western immunoblotting that the hepatic expression of CYP2C11 protein decreases in API rats. These findings suggest that inflammation occurring in peripheral tissues brings about a decrease in hepatic NTG metabolism by suppressing the hepatic expression of CYP2C11 protein, causing an alteration of the plasma concentration profile of NTG with its impaired elimination.

Assessment of effects of IR and IPC on activities of cytochrome P450 isozymes in rats by a five-drug cocktail approach

BACKGROUND AND OBJECTIVE

To evaluate the effects of ischemia and reperfusion (IR) and ischemic preconditioning (IPC) on the metabolic activities of cytochrome P450 (CYP) isozymes in rats by a five-drug cocktail approach.

METHODS

Cocktail approach was used to evaluate the influence of IR and IPC on the activities of CYP1A2, CYP2C9, CYP2E1, CYP2D6 and CYP3A4, which were reflected by the changes of pharmacokinetic parameters of five specific probe drugs: caffeine, chlorzoxazone, tolbutamide, metoprolol and midazolam, respectively. Rats were randomly divided into IR, IPC and sham groups, and then injected the mixture of five probe drugs. Blood samples were collected at a series of time-points and the concentrations of probe drugs in plasma were determined by a HPLC method with UV detection. The pharmacokinetic parameters were calculated by the software of DAS 2.0.

RESULTS

The parameters including t(1/2β), CLs, AUC, MRT and K10 exhibited a similar tendency for both IR and IPC groups. Compared with sham group, CLs and K10 of five probe drugs were significantly lower (p < 0.05), AUC and t(1/2β) of five or some probe drugs were significantly increased in IR and IPC groups (p < 0.05). Compared with IPC group, CLs of five probe drugs were decreased and AUC were significantly increased in the IR group (p < 0.05).

CONCLUSION

IR can variably decrease the activities of CYP isozymes in rats and this decrease can be attenuated by IPC.