Antipyrine metabolism during hepatic regeneration in the rat.

We investigated antipyrine clearance and urinary excretion of 4-hydroxyantipyrine, 3-hydroxymethylantipyrine and nor-antipyrine in rats after 70% partial hepatectomy. Antipyrine clearance recovered more slowly than liver weight but after 240 h both liver weight and antipyrine clearance had reached control values. During hepatic regeneration conversion of antipyrine to the three major metabolites was reduced, conversion to 3-hydroxymethylantipyrine being reduced more than conversion to the other metabolites. Antipyrine clearance was closely correlated to liver weight (r = 0.81), indicating a close relation between the functional hepatic mass and the liver weight during hepatic regeneration.