ABSTRACT
From micromanometric measurements made on liver tissue of the chicken embryo, isolated in a glucose-containing medium, estimates have been made of the rate of glucose catabolism ending in acid formation and that utilizing oxygen.
The variations undergone by these metabolic processes during normal development have been compared with the variations in mitotic activity of the hepatic cells as determined by the proportion of dividing cells seen in histological sections.
The comparison revealed two different associations in the embryonic liver between carbohydrate metabolism and mitotic activity. Before the appearance of glycogen, mitotic activity, the estimated rate of acid production from glucose, and the rate of respiratory glucose utilization decreased in a corresponding manner. After the appearance of glycogen, mitotic activity persisted, but the estimated rates of both metabolic processes fell nearly to zero.
Both before and after the appearance of glycogen these relationships of mitotic activity to carbohydrate metabolism differed from those previously recorded for the midbrain and the red-blood cells, which in turn differ one from the other. The suggestion has been made that these differences are consistent with a common dependence of mitotic activity on metabolic reactions leading to pyruvate formation, special consideration being given to the reactions of the hexose monophosphate oxidative route (Dickens, 1953), concerned in the formation of ribose-5-phosphate.
This possible dependence is considered to be additional to a dependence of mitotic activity on the energy produced from carbohydrate by the reactions of the tricarboxylic cycle. The implications of such a double dependence of mitotic activity on carbohydrate metabolism have been discussed.
There has been discussion about the most appropriate name for this metabolic pathway (Dickens, 1953). The term ‘hexose monophosphate oxidative route’, suggested by Dickens, will be used.
