A dietetic production of rickets in rats and its prevention by an inorganic salt

Abstract

The occurrence of rickets in white rats maintained under laboratory conditions has been well known to pathologists since the first publication of Morpurgo in 1900; and the essential identity of the lesions with those of human rickets has been established by the work of Morpurgo himself, of Schmorl, of Weichselbaum, and especially by the detailed histological studies of Erdheim. One of us (A. M. P.) also has had opportunity to become familiar with the disease in rats, in the course of an investigation of the possible influence of the thymus upon the teeth and skeletal system. In none of these investigations, however, were the dietary conditions of the rats standardized and controlled.

In continuing by means of feeding experiments upon rats the study of the mineral elements in nutrition which has engaged much of the attention of one of us for the past fifteen years, we have found a relatively simple diet which has led to the development of rickets in every one of the cases thus far examined; while complete protection was afforded by the addition of 0.4 per cent. of potassium phosphate (K₂HPO₄) to this diet, or (more strictly) by the introduction of this mount of potassium phosphate in place of a part of the calcium lactate which the rickets-producing diet contained.

In our experience healthy rats of families on normal diet when separated from their mothers at 28 to 30 days of age average about 40 grams in weight and a calcium content (of about 0.3 gram or 0.7 per cent. If then placed upon good diet the calcium content of the body increases in greater ratio than the body weight so that the percentage of calcium in the body rises continuously until at about four to six months of age the adult percentage of calcium—about I to 1.25 per cent. of the body weight—is reached, after which the weight of the body and the weight of calcium which it contains continues parallel until growth is complete.