Studies upon the mode of action of vitamin D

Abstract

The output of Ca and P in the feces on a Ca and P-free diet was studied a) in rats receiving 50 I.U. vitamin D daily and b) in vitamin D deficient rats. The output of endogenous Ca in the feces was increased in vitamin D deficiency, occasionally it was further increased by injection of Ca, but was not influenced by ingested P. The output of endogenous P was increased by ingestion of Ca in all rats, more in vitamin D deficient than in normal rats in a late stage of vitamin D deficiency, but was not affected by injections of Ca and P. The extra output of endogenous Ca and P play only a small role in the increased fecal output of Ca and P in vitamin D deficiency as compared with the reduced absorption of these elements.