Influence of cold and exercise in phlorhizin glycosuria

Abstract

When phlorhizinized fasting dogs with a urinary D: N ratio of 3.65: 1 are exposed to cold they at first lose extra sugar which is derived from body glycogen. But if the exposure to cold be repeated the D: N = 3.65 : 1 may remain unaltered. 1 The lowering in environmental temperature was such as would increase fat combustion in the animal by 50 per cent. and yet the sugar output remained unchanged.

Mechanical work at first brings about an increased sugar excretion. If, however, a dog be freed from glycogen mechanical work has no influence on the sugar excretion. In the following experiment a fasting dog was made use of on the third day of total phlorhizin glycosuria. He was prepared by administering cold baths on the first and second days of the glycosuria, and then exposing him to a temperature of 10° C.; shivering removed his surplus glycogen. The mechanical work was done in a wheel during five-minute intervals of alternate work and rest throughout a first hour of a two-hour period. The results were as follows:

The fat metabolism during the hour of work must have been double that of an hour of rest, and yet in the last experiment there is absolutely no change whatever in the sugar excretion as a result of travelling 1,500 meters. The D :N ratio is therefore absolutely independent of fat metabolism, but is dependent upon protein metabolism.

To illustrate the manner of sugar production from protein, glutamic acid with its five C atoms was administered subcutane-ously and per os to a phlorhizinized dog. The resulting increase in the output of urinary sugar was such as would indicate certainly a conversion of three and possibly a conversion of four of the carbon atoms of glutamic acid into dextrose.