Inhibition of precursor incorporation into nucleic acids of mammalian tissues by antimalarial aminoquinolines.

1 Chloroquine, primaquine and ethidium inhibitied thymidine incorporation into deoxyribonucleic acid of rat tissues when administered concurrently with the labelled precursor. 2 Chloroquine and primaquine inhibited the incorporation of uridine and adenine, but not orotate, into various ribonucleic acid fractions of liver of rats and mice. These drugs had no effect on leucine incorporation into hepatic protein in rats or mice. 3 Although chloroquine and primaquine are active against different stages in the life cycle of the malarial parasites, the two aminoquinolines exert similar effects in rodent tissues.