INHIBITION OF PHENACETIN- AND ACETANILIDE-INDUCED METHEMOGLOBINEMIA IN RAT BY CARBOXYLESTERASE INHIBITOR BIS-[P-NITROPHENYL] PHOSPHATE

The formation of methemoglobin caused by phenacetin and acetanilide in rats is inhibited by simultaneous treatment with if Bis-[p-nitrophenyl] phosphate (BNPP), a new carboxylesterase inhibitor, while the methemoglobinemia after p-phenetidine is not influenced by BNPP. The duration of BNPP action on phenacetin-induced methemoglobinemia and the spontaneous return of liver esterase activity after a single dose of BNPP have been studied. The enzymatic hydrolysis of the amide bond of phenacetin by rat liver, in vivo and in vitro, is inhibited considerably less by BNPP than the hydrolysis of acetanilide, monoethylglycine-2,6-xylidide and methyl butyrate, and another amidase may be involved in the deacetylation of phenacetin by rat liver. © 1969.