Changes in cellular growth in newborn rats and rabbits exposed to photoirradiation

Effects of photoirradiation from lamps currently used in phototherapy on growth in newborn rats and rabbits were studied. The newborn animals subjected to 96 h of phototherapy were found to be smaller than comparable nonirradiated animals. Mean organ weight of the brain, liver, heart and kidney was lower in the photoirradiated groups than in the nonirradiated group. DNA, protein content, protein/DNA ratio, cell number and cell size were also significantly reduced (p= less than 0.01) in the photoirradiated groups when compared to the nonirradiated group. The degree of growth retardation was more pronounced in rats subjected to continuous photoirradiation than intermittent photoirradiation (12 h on and 12 h off).