Abstract
Shipley, Kramer and Howland 1 have shown that when a section of a rachitic bone is immersed in an inorganic solution containing calcium and phosphorus, calcification occurs in the provisional zone of cartilage. This calcification resembles that occurring in vivo following the administration of an antirachitic agent to a rachitic animal. These authors have also demonstrated that calcification occurs only when the product of the concentration of the calcium and inorganic phosphorus exceeds 35. The significance of the Ca × P product in the serum of patients with infantile rickets, and animals suffering from experimental rickets, has been emphasized by Howland and Kramer 2 and confirmed by others.
The present investigation is an extension of the study of calcification in vitro, and deals with the effect of reaction (pH) on this process. The procedures employed were essentially the same as described by Shipley, Kramer and Howland, with the exception of a few technical variations. Whereas they used the McCollum No. 3143 diet in producing a rachitic condition in rats, we have employed the Steenbock diet No. 2965. The latter diet produces a very severe type of rickets within 17 days, and the sections obtained from these animals are very well adapted to an investigation of this kind, since the metaphysis is very wide and the cartilaginous zone very pronounced.
In order to study the effect of reaction, the calcium-phosphorus concentration was kept constant, and the pH varied from the acid to the alkaline sides of the physiological range. The results may be summarized briefly as follows :
1. The optimum pH for in vitro calcification, when the product of Ca × P is 50. was found to be 7.25 to 7.30.
2. Under these conditions calcification may appear after two hours' incubation.
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