Characterization of covalent binding of [14C]-2-chloro-4-acetotoluidide to microsomes of starling liver and kidney

✍ Scribed by Giri, Shri N. ;Siegel, David M.

• Publisher: John Wiley and Sons
• Year: 1991
• Tongue: English
• Weight: 794 KB
• Volume: 6
• Category: Article
• ISSN: 0887-2082
• DOI: 10.1002/jbt.2570060208

✦ Synopsis

In this study, we have characterized the covalent binding of ['4C1-2-chloro-4-acetotolui- dide (CAT) radioactivity to microsomes of starling liver and kidney. The maximal velocity ( V , , , ) of covalent binding and apparent Michaelis constant (K,) for both tissues were similar. The V , ,

for liver and kidney were 52.8 and 68.9 pmol/min/mg protein, and the apparent K,, were 0.54 and 0.87 mM, respectively. The covalent binding of radioactivity to heat-denatured microsomes of liver and kidney was reduced by 62% and 15%, respectively. Incubation at 0°C reduced the binding by 80% to liver and 70% to kidney microsomes. Absence of nicotinamide adenine dinucleotide phosphate (NADP) and molecular 0, reduced the binding to liver microsomes by 36 and 53%, as opposed to 28% increase and 26% decrease in binding to kidney microsomes, respectively. Inducers of cytochrome Pgs0 monooxygenase phenobarbital, and bmethylcholanthrene (3-MC), had opposite effects on the covalent binding of [l4C1-CAT radioactivity to hepatic and renal microsomes. Phenobarbital increased the binding to hepatic microsomes by 100% and had no effect on binding to renal microsomes. 3-MC, on the other hand, increased the binding to kidney microsomes by threefold and had no effect on the binding to hepatic microsomes. SKF 525A, an inhibitor of P450, inhibited the binding to hepatic microsomes by 60% at 0.5 mM but failed to have any effect on binding to renal microsomes. a-Naphthoflavone, another inhibitor of P450r had no effect on the covalent binding of I1'C1-CAT radioactivity to microsomes of either tissue. Addition of cysteine and glutathione in the incubation mixture inhibited the covalent binding of ra-