Proteolipid and collagen calcification, in vitro.

Initiation of in vitro calcification with insoluble type I collagen appears to be a function of tightly-bound proteolipid. The collagen preparation calcified during incubation in a metastable calcium phosphate solution before but not after lipid extraction. Calcifiability of the extracted lipid, similarly incubated, was restricted to the proteolipid fraction.