Bone histomorphometry in vitamin D-deficient rats infused with calcium and phosphorus

Publisher Website
Google Scholar
Abstract
Defective mineralization of bone and cartilage is the classical histological finding in vitamin D deficiency. Whether this represents a direct effect on mineral deposition or is a consequence of the decreased Ca and P levels that result from impaired intestinal absorption is not clear. A method was developed in which vitamin D-deficient rats have plasma Ca and P levels maintained in the normal range by continuous infusion. Histomorphometric analysis of undecalcified tibiae from these animals was compared with that of rats given vitamin D. Epiphyseal growth plate thickness, trabecular osteoid volume and mean osteoid seam width were not increased. The administration of 2 time-spaced courses of tetracycline revealed that the mineralization rate and the time interval between apposition and subsequent mineralization of osteoid (mineralization lag time) were identical to those in rats treated with vitamin D. Trabecular bone volume was increased (osteosclerosis) in the vitamin D-deficient rats. In vitamin D-deficient controls without infusions, the osteosclerosis was mostly osteoid, whereas the excess bone was well mineralized in the vitamin D-deficient rats infused with Ca and P. Osteosclerosis in vitamin D-deficient animals may result from both decreased bone resorption and increased osteoid apposition. Vitamin D evidently is not essential for mineralization in young growing rats. Decreased availability of Ca and P thus may be the sole basis of the mineralization defect seen in vitamin D deficiency.