Vitamin D sclerosis in rats

The early fine structural changes in the arteries of rats induced by excess vitamin D3 perorally or parenterally were essentially similar, except the latter had a more prominent toxic effect to the vascular wall. The ultrastructural features, incidental to calcification, included the appearance of increased ground substance with a separation of collagenous and elastic fibrils, and degenerative changes in smooth muscle cells. Atherosclerosis was greatly accelerated at the sites of vascular injury when cholesterol, cholic acid and thiouracil were added to the basal diet. Calcification was initially observed in relation to elastic fibrils or degenerated cells in the upper and middle layers of the arteries, although there were few such deposits in the thickened intima of the coronary arteries. Calcium deposition could not be a direct effect of hypercalcemia, but the functional activity of smooth muscle cells did seem to promote the mineralization of calcium and phosphate. Furthermore, vitamin D-induced sclerosis did not prevent intimal thickening of the arteries when vitamin D3 was withdrawn.