ULTRASTRUCTURE OF CALCIPHYLAXIS IN SKIN

Rats weighing approximately 100 grams were given, by stomach tube, dihydrotachystrol (DHT) in corn oil. After 29 hours a small area of the skin on the dorsum of the neck was traumatized by pinching it with hemostats. The animals were divided into ten groups and sacrificed after trauma; 5 minutes, 10 minutes, 30 minutes, 1 hour, 2 hours, 4 hours, 8 hours, 16 hours, 24 hours, and 48 hours. These specimens were fixed in osmium and embedded in Epon for electron microscopy. Except for the crush damage as a result of the trauma, the cells of the dermis and epidermis showed little change until 4 hours, when the fibrocytes began to accumulate electron dense material in their mitochondria, and the Golgi complex became larger demonstrating large vesicle formation on the Golgi secretory face. The electron dense material in the mitochondria was lost contiguous with the accretion of electron dense material in the large Golgi vesicles of the involved fibrocytes. Microincineration demonstrated a significant accumulation of mineral ash within the mitochondria and vesicles. Vesicles were secreted from the cells into the matrix by 24 hours, and by 48 hours apatite formation was observed within the vesicles and extended from them to the surrounding collagenous matrix. The fibrocytes that produced mineral laden vesicles showed normal ultra-structure following loss of vesicles. The calci-phylactic response involves selective cell calcium and phosphate sequestration into mitochondria, coupled with intracellular production of mineral loaded vesicles that directly nucleate matrix mineralization following secretion.. Pretreatment of rats with 2mg/Kg EHDP for 6 days is characterized by an absence of mineral laden vesicles. Comparable vesicles are not noted in normal cartilage, bone or skin. Osmium pyroantimonate fixed cartilage, however, does demonstrate mineral containing microvesicies in the cytoplasm. © 1978.