Abstract
Levels of dihydrofolate reductase (DHFR) were measured in livers from man and a variety of animals and birds to explore possible causes for the remarkably low levels of DHFR previously reported in fresh human tissues, including liver (Cancer Drug Delivery 2, 133 (1985)). While levels were lower in wild than domesticated animals and birds, suggesting a possible role for folic acid supplements fed to the latter, levels in both were far higher than in humans. Hepatic DHFR levels were similar in adult and young animals, birds and humans. In primates, monkey livers had DHFR levels similar to those of other animals, while levels in great apes were much lower and closer to levels in man. These findings suggest that low levels of DHFR are a feature peculiar to man, which is shared with the primates closest to man, but which distinguishes him from most animals and birds.
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