The significance of the non-protein nitrogen of the blood in experimental uranium nephritis

Abstract

The increase in the non-protein nitrogen content of the blood in the experimental uranium nephritis of dogs may be due to:

1. Diminished secretory activity of the kidney. This is undoubtedly the case in those instances of severe nephritis in which the urinary nitrogen is diminished.

2. Increased protein catabolism. In poisonings of less intensity but sufficient to produce a nephritis of considerable severity as indicated by the albuminuria, there may be an increased amount of nitrogen in the urine as compared to the intake. In these instances the amount of non-protein nitrogen in the blood rises considerably. Such an increase, not being due to nitrogen retention on the part of the kidney, may be ascribed to an increased protein catabolism.

3. Inspissation of the blood. A polyuria, resulting in loss of water to the animal in this form of nephritis, may cause an apparent rise in the non-protein nitrogen of the blood.

4. The chemical combination in which the non-protein nitrogen of the blood exists. Animals with a certain degree of uranium nephritis are capable of putting out extremely high amounts of nitrogen in the urine. (A dog of 15 kilos daily eliminated 23 gm. of nitrogen, half of which was given as urea, throughout a uranium nephritis without any retention.) This would seem to indicate that the increase in non-protein nitrogen of the blood in such animals is due in part to an abnormal chemical combination which can not pass the kidney and is not necessarily due to impaired kidney function.

Before ascribing an increase in the non-protein nitrogen of the blood in any form of nephritis to kidney insufficiency, the influence of all the above factors should be taken into account.