Inhibition of catalase in vitro and in vivo by 4-hydroxypyrazole, a metabolite of pyrazole.

For many years it has been recognised that not all the properties of pyrazole are due to the molecule itself [l-4]. With the elucidation of the metabolism of pyrazole [S] it was appreciated that several metabolites could possess biological activity. In {6] an in vitro inhibition of catalase (EC 1 .l 1 .1.6) by 4-hydroxypyrazole (4-HP), one of the major metabolites of pyrazole was reported. This paper confirms the inhibition of catalase by 4-HP but also describes the importance of incubation time, a factor not studied earlier. We also describe the effects of 4-HP administration to mice on liver catalase activity.