An investigation of calcium intake, 1-alpha(OH)D 3, and etidronate on bone

Abstract

The synthetic metabolite of vitamin D 3 [1α(OH)D 3] caused a significant plasma calcium elevation in rats only when dietary calcium was low. Animals given the low calcium diet (0.005%) had lower plasma parathyroid hormone (PTH) levels when the diet contained 1α(OH)D 3 and significantly higher levels than animals on a high calcium (0.95%) diet, with or without the vitamin. The nutritional stress of a low calcium diet without 1α(OH)D 3 resulted in a prolonged severe hypocalcemia and elevated serum PTH levels. A higher ash, phosphate, and calcium content was found in the bones of animals fed the high calcium diet, with no vitamin D 3 that were given etidronate (EHDP). When animals received the same calcium diet with 1α(OH)D 3 supplementation, EHDP administration increased the percentage of bone ash but had no effect on ash weight. 1α(OH)D 3 or EHDP did not affect ash weight, dry fat free weight, and percentage of ash of bone of animals receiving a low calcium diet. The percentage of calcium and phosphorus in bone ash was similar among all groups, although the amounts per humerus were characteristically related to the calcium intake. There was approximately 20–25% less bone mineral and calcium and phosphorus in the humeri of low calcium intake animals than in animals provided an adequate dietary calcium.