The Source of Urinary Proteins.

It was previously reported by one of us 1 that complete picture of uremia in all its clinical, pathological and chemical details could be produced by the injection of hypertonic salt solutions into animals already made acid by the absorption of autogenous edema fluid. In these animals, although the kidneys remained histologically normal, there were evidences of degenerative changes in the liver. It was thought possible that the proteins in the urine in these experiments originated in the liver, and were the exciting cause of the renal changes which afterwards made the kidneys permeable to blood proteins. It is well known that foreign proteins injected into the blood are excreted almost quantitatively and that after a certain period the kidneys are thus rendered permeable to blood proteins as well.

Proteins from these artificial uremias and also those in the urine of dogs with ether nephritis were studied. Rabbits were sensitized to dogs' blood proteins by the subcutaneous injection of dog serum in the following series of doses: 1, 2, 4, 6, 8, and 10 cc. at 3 day intervals. The rabbits were sacrificed on the 21st day and bled. Sera thus obtained will react to dog blood proteins in dilutions of 1/1,000,000.

Urines were collected from our experimental nephritides in small 15 minute samples. Each sample was tested first for traumatic blood, which often spoiled the experiments. Next, all blood-free samples were tested for albumen and on all positive specimens, were tested against the serum. These tests were carried out both on whole urines and on urinary proteins, purified by dialysis and precipitation by ammonium sulphate saturation. From the earlier samples in a large series of experiments over 100 specimens were found in which the urinary proteins were free from serum proteins.