The effects of hibernation on the in vitro synthesis of DNA by hamster lymphoid tissue

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Abstract
DNA synthesis was studied in vitro in lymphoid tissue taken from hibernating, cold adapted and active golden hamsters in an attempt to elucidate the mechanism of suppressed DNA synthesis during hibernation. The rates of DNA synthesis at temperatures varying from 4 to 37°C were greatest in cells from active animals, less from cold adapted and least from hibernating animals. The depression in cells from cold adapted animals was 70% reversible by returning the animals to a warm environment 40 minutes before they were sacrificed but the hibernating animals had to be aroused for more than 12 hours before their rates recovered, suggesting a different mechanism responsible for depression in these two instances.Radioautographic and biochemical measurements of DNA synthesis in cells taken from hibernating animals indicated that the depressed synthesis seen during hibernation is the result of a reduction in the percentage of cells engaged in DNA synthesis. This implies that the low body temperatures of hibernation produce a block in the cell cycle of lymphoid cells not unlike that observed when other mammalian cells are exposed to cold in vitro.