Analysis of changes in collagen biosynthesis that occur when chick chondrocytes are grown in 5-bromo-2'-deoxyuridine

Chick embryo chondrocytes, in primary culture, initially synthesize only Type ii collagen (chain composition, [alpha1(II)13), as judged by two criteria: (i) carbosymethyl-cellulose chromatography of the denatured collagen, and (ii) carbosymethyl-cellulose chromatography of the cyanogen bromide peptides derived from the isolated chains. After a period of growth in 5-bromo-2'-deoxyuridine, however, synthesis of two different types of collagen could be detected after differential salt precipitation of the newly synthesized native collagens from neutral salt solutions at 2.2 M NaCl and subsequently at 0.01 M Na2hPO4. By criteria indicated above, the collagen precipitating at 2.2 M NaCl was identified as Type I collagen (chain composition, [alpha(I)]2alpha2), whereas the collagen subsequently precipitated at 0.01 M Na2HPO4 was found to be comprised entirely of alpha1(I) chains, indicating a chain composition, [alpha](I)]3. We propose to designate the latter type of molecule as the Type I trimer.