Differential inhibitory effects of phenytoin, diclofenac, phenylbutazone and a series of sulfonamides on hepatic cytochrome P4502C activity in vitro, and correlation with some molecular descriptors in the dwarf goat (Caprus hircus aegagrus).

Article Details

Citation Copy to clipboard

Zweers-Zeilmaker WM, Horbach GJ, Witkamp RF

Xenobiotica. 1997 Aug;27(8):769-80.

PubMed ID

9293615 [ View in PubMed

]

Abstract

1. The aim of the present study was to investigate the potency of various sulfonamides to inhibit tolbutamide hydroxylation (a CYP2C activity) in hepatic microsomal fractions and hepatocytes of the dwarf goat. Also a number of suggested substrates for human CYP2C9 was investigated. 2. From Dixon plots (microsomal fractions) it was observed that all compounds were competitive inhibitors of tolbutamide hydroxylation. Phenytoin (PT) showed the lowest Ki. Ki for the sulfonamides ranged between 205 and 4546 microM, sulfadoxine having the lowest Ki followed by sulfadimethoxine, sulfamoxole, sulfadimidine and sulfaphenazole. 3. In hepatocytes sulfaphenazole and diclofenac were the most potent inhibitors. 4. Out data indicate that PT, diclofenac (DF) and phenylbutazone (PBZ) are relative strong competitive inhibitors of tolbutamide hydroxylation and they are probably also substrates for the same enzyme. Differential inhibition of tolbutamide hydroxylation by sulfonamides was observed. 5. Correlation of structural parameters with the inhibition constant or the inhibition in hepatocytes showed that molecular volume, polarizability and molecular surface area are important parameters in determining the rate of inhibition of tolbutamide hydroxylation by sulfonamides in both microsomes and hepatocytes. In addition, log Poct are also involved in determining inhibition constants in microsomal fractions.

DrugBank Data that Cites this Article

Drug Enzymes

Drug	Enzyme	Kind	Organism	Pharmacological Action	Actions
Sulfamoxole	Cytochrome P450 2C9	Protein	Humans	Unknown	Inhibitor	Details