Analysis of the collagenous products synthesised in vitro by chick blood vessels: alterations during development and effects of serum on the pattern of synthesis.

Chick blood vessels synthesise in vitro collagens types I and III and, in much smaller amount, type V. In the presence of beta APN during synthesis, type I collagen is easily extracted whilst, in contrast, types III and V are insoluble and require the use of pepsin for their release into solution. The ratio of collagen type I to type III decreases during the course of development from around 9:1 in the young (11-day) embryo to a value approaching unity in the young chick. Type V collagen increases relative to the interstitial collagens. The synthesis of 'short-chain' and 'endothelial' collagens was not detected with certainty. Evidence for the possible synthesis of type IV and of additional, collagenase-sensitive, non-reducible, low-molecular weight species is presented. The presence of serum increased the proportion of collagen type I relative to that of type III. This appeared to be due in part to a direct stimulation of type I synthesis by serum but also in part to the replacement by serum of tissue 'factors' (or inhibitors of degradation) removed from the tissue during its preincubation with unlabelled medium.