Temporal changes of gene expression in rat kidney and lung, and the effect of prior growth inhibition on these changes

Temporal changes of gene expression from 1-wk- to 5-wk-old rat in kidney and lung, and the effect of prior growth inhibition on these genetic changes. In mammals, body growth is rapid in early life but decelerates with age. Somatic growth deceleration is caused by a gradual decline in cell proliferation that occurs simultaneously in many different organs, but is not caused by a hormonal mechanism. We hypothesize that growth deceleration is driven by a postnatal genetic program that occurs coordinately in multiple organs. Using microarrays, we investigated the changes of gene expression that occur with age in kidney and lung as growth slows down, and also investigated whether these changes were growth-driven, by asking whether prior delay of postnatal growth caused by malnutrition (tryptophan deficiency) would also delay these genetic changes. To compare gene expression between fast-growing animals and more slowly growing animals, we extracted total mRNA from kidney and lung in 1-wk-old and 5-wk-old mice (5 animals each). Then, to investigate the effect of prior growth on these genetic changes, we also extracted total mRNA from kidney and lung in 5-wk-old mice that received a tryptophan-deficient diet from birth to 4wk of age.