Heterotopic calcification in swine.

Pigs on nutritional studies developed heterotopic calcifications in the left atrial endocardium, submucosa of the gastric fundus and to a lesser extent in other sites. Light and electron microscopy of mineralized tissue showed early edema and connective tissue change, deposition of calcium, granulomatous reaction and repair. There was no alkaline phosphatase activity at the sites of calcification and the distribution of this enzyme activity was normal in other tissues. Increased acid phosphatase activity was demonstrated only in the lysosomes of macrophages in areas of granulomatous inflammation. Calcium and magnesium were within normal range in serum and femoral bone. The character and distribution of the lesions suggested the possibility of protracted low grade hypervitaminosis D3.