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The initial expression of hepatic aldehyde oxidase (EC 1.2.3.1, oxidoreductase) and the pattern of changes in enzyme activity throughout development and maturation were measured in C57BL/6J male and female mice. The developmental formation of enzyme activity during the latter part of fetal life was correlated with developmental changes in the hepatocyte population. Aldehyde oxidase was usually detectable in measurable quantities in both sexes at 16 days gestation. Although there was a significant difference in enzyme activity between sexes at this gestational age, there was no significant difference between sexes at any other stage of fetal development. The accumulation of enzyme during gestation appeared to be due to an increase in synthesis per hepatocyte and not to an increase in the numbers of hepatocytes alone.

The effects of sex hormones on the activity of a hepatic enzyme, aldehyde oxidase (EC 1.2.3.1, an oxidoreductase), in sexually immature and mature C57BL/6J mice has been investigated. The androgens testosterone propionate and dihydrotestosterone significantly increased enzyme levels in castrated adult males and intact adult females, whereas beta-estradiol-3,17-dipropionate significantly decreased enzyme levels in adult male mice. Increased levels of aldehyde oxidase could not be achieved in immature males with either androgen. Sucrose density gradient ultracentrifugation of hepatic cytosol and 3H-androgen revealed a macromolecular binding complex sedimenting at 4.6 S which, by careful examination, appeared to represent serum contamination of the cytosol preparation.