Presence of lactate dehydrogenase-containing vesicles in an intramembranous ossifying tissue: new-born mouse calvaria.

Lactate dehydrogenase-containing vesicles have been isolated from the extracellular matrix of the calvaria of new-born mice. The calvariae, intramembranous ossification tissue, were removed from 2-day-old mice, followed by the separation of the extracellular matrix vesicle fraction after collagenase digestion. Lactate dehydrogenase-containing vesicles with a density different from that of matrix vesicles were detected in the matrix vesicle fraction. Lactate dehydrogenase in these vesicles did not result from cell lysis and vesicle capture during the preparation of the matrix vesicle fraction. The isoenzyme pattern of lactate dehydrogenase in lactate dehydrogenase-containing vesicles was nearly identical to that of cytosolic lactate dehydrogenase of the cell fraction. Other cytosolic enzymes were not detected in lactate dehydrogenase-containing vesicles, suggesting the presence of a mechanism for specific uptake of cytosolic lactate dehydrogenase during the in vivo formation of the vesicles. This is the first report on the presence of lactate dehydrogenase-containing vesicles in the intramembranous ossification site.