Abstract
The rapid onset of a marked fasting ketosis following low protein diets has been attributed by MacKay et al. 1 , 2 to a lack of “stored” protein available for the formation of antiketogenic material during fasting. Their conclusions were based on the higher nitrogen excretion observed during fasting after the high protein intakes. The difference in nitrogen excretion between groups on 5 and 25% protein diets averaged approximately 6 mg per square decimeter of body surface per day during the first 48 hours. In a comparable experiment we observed a difference in excretion of 8 mg of nitrogen. It seemed unlikely that 30 mg of glucose per square decimeter of body surface, the amount available from the metabolism of protein containing 8 mg of nitrogen, would have an appreciable effect on the metabolism of the rat. However, Deuel 3 has reported a marked lowering of ketonuria after giving 100 mg of glucose per square decimeter of body surface daily.
The present study was designed to determine the effect of glucose available from the additional protein metabolized after higher protein intakes upon fasting ketonemia in the rat. Two groups of 12 male rats, weighing approximately 224 g, were fed for 3 weeks a 5% protein, high fat diet similar to that used previously 4 and then fasted for 48 hours. Twice daily during the fasting period one group received intraperitoneally a 5% glucose solution containing 15 mg of glucose per square decimeter of body surface. The other group received similar volumes of normal saline.
The blood ketone levels at the end of the 48-hour fast were 25.6 ± 1.3∗ mg % of acetone in the glucose injected animals and 28.5 ± 1.0 mg % for the controls.
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