[Aortic myocytes and calciferol-induced arterial calcification: ultrastructural and biochemical study].

Thirty0seven rats were given Vitamin D2 orally at the daily dose of 4000 I.U. for two months, then 8000 I.U. for the following two months and 26 rats were used as controls. Batches of both intoxicated and control rats were sacrificed on the 15, 30, 45, 90 and 120 days after the onset of the experiment. This chronic calciferol intoxication allowed a better understanding of the calcifying process. Modified myocytes were observed early and for a long time in and around the mineralizing foci. They had the ultrastructural and histochemical characteristics of cells with an activated metabolism: excessive development of the organelles linked with synthesis processes, hyperactivity of phoshatases, of lysosomic enzymes and of enzymatic systems of cell respiration and glycolysis. Some data of the present study support the hypothesis that myocytes may be a local factor for the aortic calcification process: by increasing the conjonctive constituents calciphily, by producing phosphate and sulphate anions as well as calcifiable organic materials (glycoproteins, GAG), by modification in their own environmental physico-chemical conditions favorous to calcium precipitation (acidosis, phosphate and sulphate anions supersaturation).