Metabolism of calcium, phosphorus and nitrogen in hypervitaminosis A in young rats

Abstract

Oral administration of a pure vitamin A preparation at a dose 400 times the normal requirement produces effects such as reduced food intake, loss of weight, skeletal fractures and hemorrhages in young albino rats. The degree of toxicity is approximately proportional to the total quantity of vitamin A administered. The effects of administration of large doses of vitamin A on the metabolism of Ca, P and N were also studied A negative balance for Ca, P and N sets in and continues for a considerable period after the administration of large doses of vitamin A has ceased. No changes were detected in the levels of Ca and inorganic P of the blood. Very little change in the relative mineral composition of the bones was observed. Increased excretion of Ca and P is therefore probably due to thinning of the bones. Estimation of vitamin A in the liver suggests that administration of amounts of vitamin A, several times greater than the normal requirements, reduces the absorption of vitamin A from the intestine.