Dna Metabolism in Perfused Organs: II. Incorporation Into Dna and Catabolism of Thymidine at Different Levels of Substrate by Normal and X-Irradiated Liver and Intestine

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Abstract
Normal, regenerating and regenerating X-irradiated liver as well as normal and X-irradiated intestine and kidney were perfused with addition of different quantities of C14-and H3-thy-midine. Formation of thymine, dihydrothymme, β-aminoiso-butyric acid (BAIBA) and incorporation into DNA were determined. Only liver is capable of degrading thymidine to BAIBA and beyond. Catabolism of thymidine in the liver is extremely rapid and more than 100 times the quantity normally degraded can be handled by the liver. Regenerating liver degrades slightly less thymidine than normal liver, presumably due to the fact that the DNA synthesizing cells do not catabolize. A new technique for perfusing isolated intestine under physiological conditions is described. The perfused intestine degrades thymidine only to thymine and dihydrothymme, but incorporation into DNA is very active.