Rickets in Rats. VI. ∗ Effect of Phosphate Added to the Diet of Non-Ricketic Rats.

Phosphate added to the diet causes rapid healing of rats made ricketic on a high calcium-low phosphorus regimen which has not been irradiated and is poor in vitamin D. This is evidenced by histological sections of the bones, blood serum analyses, bone analyses and studies of the metabolism of calcium and phosphorus. 1 As a result of the alteration in diet not only is the rickets cured but a transient tetany is also produced. The blood serum phosphate becomes extremely high—the calcium low. If the animals survive the tetany the blood serum calcium and phosphorus return to values considered normal in 2 weeks. Similarly, the feeding of phosphate to normal dogs is known to produce tetany (Salvesen, Hastings and McIntosh 2 ).

When the diet for rats was altered by the addition of phosphate it was not considered a high phosphorus diet. It was known from the studies of McCollum et al. 3 to produce normal rats. The question accordingly arises whether non-ricketic animals shifted from a diet of low phosphorus to one of moderate phosphorus content would develop tetany. If so, would this be of short duration like that observed in the cure of rickets? Or is there something in the condition called rickets which predisposes to an exaggerated effect of phosphate?

Plan—Rats fed with diets of a high calcium low phosphorus content and a liberal supply of anti-ricketic agents were compared to those fed on the same diet without vitamins. After 3 weeks on this diet all were given enough phosphate to make the Ca/P ratio 1/1. Seven and 14 days later the blood serum was analyzed for calcium and inorganic phosphorus, histological preparations of the bones were made, and the percentage ash in the fat-free bones was determined.