Influence of parathyroid hormone on ultrastructural and enzymatic changes induced by vitamin D in bone of thyroparathyroidectomized rats
Weisbrode, S.E.; Capen, C.C.; Nagode, L.A.
Laboratory Investigation; A Journal of Technical Methods and Pathology 30(6): 786-794
1974
ISSN/ISBN: 0023-6837 PMID: 4275650 Document Number: 79499
Osteocytes and osteoblasts in thyroparathyroidectomised male Sprague-Dawley rats, treated with cholecalciferol by mouth, showed ultrastructural changes indicating increased activity of bone cells and acceleration of the osteocyte-osteoblast Ca pump; lacunar walls were occasionally devoid of mineral suggesting mobilisation of hydroxyapatite crystals; osteoclasts were inconspicuous. Bone cells from thyroparathyroidectomised rats given cholecalciferol and parathyroid extract were also metabolically active and had additional ultrastructural changes not occasioned by vitamin D or parathyroid extract alone; many osteoblasts had mineral deposits along the plasma membrane and bone alkaline phosphatase and calcium adenosine triphosphatase activities were greatly increased. Although most osteocytes appeared similar to those treated with cholecalciferol alone, the lacunae of some cells had evidence of both mineral and collagen destruction, indicating osteocytic osteolysis. Osteoclasts were more frequent in rats receiving cholecalciferol and parathyroid extract, but their fine structural characteristics did not differ from those in rats given cholecalciferol alone. When dietary Ca intake was minimal, mineral mobilisation from bone was sufficient for both cholecalciferol alone and cholecalciferol with parathyroid extract to raise serum Ca above postoperative values, but serum Ca was significantly lower in rats given cholecalciferol with parathyroid extract.