Renal Damage Following the Administration of Inorganic Phosphate.

Abstract

In an earlier communication 1 it was reported that the addition of acid or basic sodium phosphate was followed by a remarkable increase in the size and weight of the kidneys. Further experiments have demonstrated that these changes take place with the addition of an adequate quantity of inorganic phosphate in many forms to the diet of young albino rats. These include the sodium and potassium salts, either primary, secondary, tertiary, or neutral mixtures and phosphoric acid itself. The phosphate concentration used in most of the experiments was essentially the same as that which was used in the earlier experiments 1 with a 4 calorie per gram diet, although a quarter of this concentration was found to produce abnormal kidney changes. An examination of the histological structure of these kidneys, 250 in all, has made us aware of interesting pathological changes.

The lesions noted in the kidneys of all the animals irrespective of variation in the nature of the salt fed, was essentially similar and consisted of epithelial destruction with later reparative processes. Cloudy swelling and necrosis of the cells of the convoluted tubules followed by regeneration were noted in all of the various experiments, including those of from 3 days'duration to the longest period used (44 days). Associated with these processes there occurred calcification of the necrotic debris which accumulated as a result of them so that calcified tubular casts filled the tubule lumen. In those animals that had been fed the phosphate diets for considerable periods of time, proliferative processes were also noted in the interstitial connective tissue about those tubules which had suffered most severely.

All these changes were localized to a very definite portion of the kidney, namely the outer zone of the medulla where the terminal portions of the proximal convoluted tubule dip into the substance of the medulla.