The Distribution of Glucose in Human Blood

Glucose is readily soluble and so far as we know readily permeates the red blood cells. Unlike electrolytes, there is no reason to suppose that the conditions which determine the distribution of electrolytes on the two sides of the erythrocyte “membrane” would influence its distribution, so that it is reasonable to believe that the concentration of glucose in the plasma and erythrocytes would be according to the water concentrations of these media. Although there are scores of observations reported in the literature concerning the distribution of sugar between the corpuscles and plasma of the blood of man and various animals, none of them to our knowledge considers this point directly. The earlier investigations have been summarized by Macleod (1) and the more recent ones by Somogyi (2) and others (3, 4). In examining the published data it is obvious in most instances, on the basis of the usual fluid content, that the concentration of sugar in the cell water is a great deal higher than in the water contained in the plasma. However, all of these investigators assumed all of the reducing substance in the blood to be glucose, and this is not the case. The nature and red blood cell permeability of the nonglucose fraction which is not absorbed by yeast is unknown. Since the concentration of this non-glucose-reducing fraction in the erythrocyt’es has been found (2) on a volume basis to be about 5 times that of plasma, a source of gross error in most blood sugar distribution studies is evident. Somogyi (2) has ruled out this inaccuracy and dealt with true in place of apparent glucose values which had always been used heretofore. This reduced the ratio Corpuscle sugar concentration Plasma sugar concentration (by volume) to nearer a point which