The influence of carbohydrate on the protein metabolism of a fasting pregnant dog

A dog in the ninth week of pregnancy and weighing 12.46 kgm., on the third fasting day of a three-day period was fed 42 gm. of cane sugar for two days. The reduction in the nitrogen elimination on the second sugar day as compared with the last fasting day was over 50 per cent. The same experiment was repeated on the same dog more than two months later, i. e., four weeks after the puppies were weaned. The dog weighed on the third fasting day 10.42 kgm. Since the puppies when they were born (four days after the conclusion of the former experiment) weighed 1.5 kgm., this probably represents, as nearly as one can estimate, the weight of the mother alone at the time of the former experiment. The cane sugar fed, therefore, would represent about the same percentage of the actual requirement on the part of the mother dog in both cases. The reduction of the nitrogen elimination on the second sugar day as compared with the fasting day just preceding, was 20 per cent. in the non-pregnant condition instead of 50 per cent. in the pregnant condition.

The greater effect of the sugar in the former experiment is due to a large relative, as well as an absolute, reduction in the urea plus ammonia nitrogen. The explanation might be either that the sugar interfered with the production of urea and ammonia, that is, with deamidization and dehydration of the proteins placed in circulation when fasting is superimposed on the pregnancy, or that the sugar has helped in the utilization of such proteins for the maintenance of the fetal growth. The latter is, I think, the better interpretation. It would stem that the sugar has diverted substances which would otherwise have been eliminated as urea or ammonia, and it seems probable that this has been accomplished by synthesis in the embryonic tissues.