Dogs were made hypoproteinemic by repeated injections of gum acacia, and the acacia injections were discontinued. Diets of varying protein content were then given. When a high protein diet is provided the plasma protein concentration increases; with a low protein diet, or under conditions of fasting, the plasma protein concentration diminishes. Similarly, plasma acacia concentration shows increases and decreases which are reciprocal to the protein variations. Total circulating plasma protein and total circulating plasma acacia show similar changes. In all instances total circulating colloid (acacia plus protein) concentration adds up to an amount within normal limits for protein alone.

The results indicate that under these conditions, acacia stored in the body (principally in the liver) can be removed from its site of deposit and returned to the blood.

The data also show that dogs in which acacia is deposited in large quantities, require a larger amount of protein in the diet to maintain a constant plasma protein content than do normal dogs.

It appears that the mechanism for maintenance of peripheral colloidal material may be dependent on differences in intracellular and extracellular colloidal osmotic pressure. The experiments also support the idea that plasma protein molecules, as well as gum acacia, may pass in and out of cells through the cell membranes.

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