[Cutaneous calcinosis induced by topical calciphylaxis in rats. I. Ultrastructural aspcts].

Skin calcification induced by topical calciphylaxis was provoked by a subcutaneous injection of iron chloride in rats previously sensitized by D.H.T. and studied by electron microscope. The evolution of the calciphylatic response can be resumed as follows: -- early appearance of numberous granules in the mitochondria of the cells of the connective tissue; their inorganic nature was revealed by microincineration and it is highly probable that they are a reserve of mineral ions; -- between the 6 hr, and the 18 hr, stages the interfibrillar matrix contained rounded vesicular structures, enclosed by a triple mambrane, which must surely be of cellular origin; they progressively incorporated more and more mineral particles which confirm their primordial role in the initial phases of mineralization; -- from the 14 hr. stage onward, mineral rodlets composed of chains of little dots appeared in the intercellular matrix and then on the collagen fibrils, probably in contact with the mucopolysaccharides; -- starting at the 24 hr, stage, the mineralization progressed without a vesicular intermediary forming increasingly dense and widespread plaques; the presence of needles of homogenous aspect indicated the appearance of a crystalline mineral deposit; an intrafibrillar mineral deposit becomes visible later. These results are compared with those obtained previously in other studies of experimental or pathological calcinosis and of mineralization of skeletal tissues.