New Zealand rabbits were subjected to 500 rads of total-body irradiation. Bone marrow cells, 24 hr after irradiation, were incubated with <tex-math>$[{\rm U}\text{-}{}^{14}{\rm C}]$</tex-math> glucose for various time intervals, or with <tex-math>$[1\text{-}{}^{14}{\rm C}]{\rm K}^{+}\text{-palmitate}$</tex-math>. Ionizing radiation increased oxidation of <tex-math>$[{\rm U}\text{-}{}^{14}{\rm C}]$</tex-math> glucose while [14 C] palmitate oxidation was inversely affected. <tex-math>$[{\rm U}\text{-}{}^{14}{\rm C}]$</tex-math> Glucose is incorporated mainly as glycerol into neutral lipids and phospholipids. The major products of lipid biosynthesis from both precursors are triglycerides and phosphatidyl choline. Ionizing radiation increased the biosynthesis of triglycerides and phosphatidyl choline and decreased the percentage of total radioactivity incorporated into phosphatidyl ethanolamine. It is suggested that accumulation of lipids in the bone marrow of irradiated animals is partly due to increased lipogenesis. An explanation of this phenomenon is provided by the increased glucose catabolism through which increased glycerophosphate may be available for lipid biosynthesis.

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