Studies on the mode of action and the metabolism of vitamin D

Abstract

Summary 1.The oral administration to rabbits of 20 c.c. of viosterol in oil (200,000 international units of vitamin D, equivalent to approximately 1.6 mg. of irradiated ergosterol) led to an increase in the inorganic phosphorus content of the blood without correspondingly affecting the blood calcium content. This action took place about five days after the viosterol had been given and lasted until the tenth to the fifteenth day. 2.In order to learn whether or not this action might be due to the stimulating effect of vitamin D upon an endocrine gland, thus leading to the production of a phosphate hormone, the serum of these rabbits was tested on rachitic rats. The rabbits' blood was obtained five days after the viosterol had been given and was found to cure rachitic rats in from eight to ten days if 0.6 c.c. of the serum was daily injected intramuscularly. 3.No evidence was found, however, to justify the assumption that any substance other than irradiated ergosterol was present in this serum or was even partly responsible for its curative potency, because the rickets-curing substance of this serum was soluble in ether and in oil, was destroyed completely by overirradiation with ultraviolet rays, and was found not to be ultrafiltrable. 4.When viosterol was given by mouth to rabbits in a single dose corresponding to approximately 1.6 mg. of irradiated ergosterol, detectable amounts of vitamin D were found to be circulating in the blood for from two to three months. Summary 1.The oral administration to rabbits of 20 c.c. of viosterol in oil (200,000 international units of vitamin D, equivalent to approximately 1.6 mg. of irradiated ergosterol) led to an increase in the inorganic phosphorus content of the blood without correspondingly affecting the blood calcium content. This action took place about five days after the viosterol had been given and lasted until the tenth to the fifteenth day. 2.In order to learn whether or not this action might be due to the stimulating effect of vitamin D upon an endocrine gland, thus leading to the production of a phosphate hormone, the serum of these rabbits was tested on rachitic rats. The rabbits' blood was obtained five days after the viosterol had been given and was found to cure rachitic rats in from eight to ten days if 0.6 c.c. of the serum was daily injected intramuscularly. 3.No evidence was found, however, to justify the assumption that any substance other than irradiated ergosterol was present in this serum or was even partly responsible for its curative potency, because the rickets-curing substance of this serum was soluble in ether and in oil, was destroyed completely by overirradiation with ultraviolet rays, and was found not to be ultrafiltrable. 4.When viosterol was given by mouth to rabbits in a single dose corresponding to approximately 1.6 mg. of irradiated ergosterol, detectable amounts of vitamin D were found to be circulating in the blood for from two to three months.