1) The influence of choline on the nonprotein respiratory quotient (R.Q.) was examined in the albino rats.
2) The R.Q. in the 24-hour-fasted rats was 0.80, indicating that a significant amount of carbohydrate was still oxidized, whereas in the 48-hour-fasted rats the R.Q. was 0.71, indicating that fat was oxidized almost exclusively.
3) When choline was injected to the 48-hour-fasted rats, protein catabolism was markedly depressed and the oxidation of fat was augmented.
4) The administration of glucose raised the R.Q. to 0.90 in the 48-hourfasted rats. However, if these animals had received the injection of choline, the R.Q. was 0.68, indicating that the oxidation of carbohydrate was strongly inhibited and the oxidation of fat was augmented.
5) The R.Q. in the 24-hour-fasted rats was 0.80 as described above, whereas that in the adrenalectomized or hypophysectomized rats was decreased to 0.72. It is evident from these results that the oxidation of carbohydrate was depressed in these animals.
In consideration of the results obtained in the experiments by Okada
6) and Nakata
et al.7) which pointed out the inhibitory action of choline on the adrenocortical function, the inhibition of carbohydrate oxidation by the injection of choline as shown in the present experiment may be ascribed to the lowered adrenocortical function.
6) Catabolism of protein in the 24-hour-fasted rats was decreased by the adrenalectomy and it was still decreased by the injection of choline.
7) According to the above results, the injection of choline augments the oxidation of fat through its inhibitory action on the oxidation of carbohydrate and protein in the body. This effect of choline may be ascribed to the inhibition of the adrenocortical function. The data also indicated that choline inhibits the development of fatty livers without inhibiting the oxidation of fat as an energy source.
The authors wish to express sincere thanks to Emeritus Professor Y. Sueyoshi for his unfailing guidance throughout the course of this work and in the preparation of this treatise.
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