ROWE. Hypoxia and malnutrition in newborn rats: effects on RNA, DNA, and protein in tissues. Am. J. Physiol. 217(3): 642-645. 1969.-Newborn male rats were exposed to 12% oxygen from 1 to 7 days and their brain weights, DNA, protein, or RNA content studied at 7, 21, or 35 days. At 35 days, studies were made of cerebrum and cerebellum and of the liver, muscle mass, carcass fat, and skeletal collagen. These rats were compared with normal rats and with rats malnourished from 1 to 7 days. Hypoxia caused a failure of brain DNA and protein content to increase. At 35 days, the hypoxic rats had reduction in body weight, cerebellar weight, liver weight, muscle mass, muscle cell number, and skeletal collagen. There was an increase in carcass fat. The cerebellar DNA and protein content were reduced whereas in the cerebrum, liver, and muscle, the RNA content was very low (not measured in cerebellum). It is concluded that during hypoxia cell multiplication is prevented, but subsequently there is interference with RNA production and protein synthesis with growth retardation. In the brain the cerebellum is damaged more than the cerebrum. The effects of hypoxia can not be ascribed entirely to restricted food intake.