Chick embryos were sacrificed at intervals after simultaneous injection of BAPN and proline-C14, the collagen separated into neutral salt-extractable and residue fractions, and total hydroxyproline and hydroxyproline specific radioactivity determined in each fraction. Extractable collagen, measured as hydroxyproline, increased markedly and had a higher specific activity in BAPN-treated embryos than in corresponding controls. Hydroxyproline of the residue collagen in the treated animals, however, had a lower specific activity.

When proline-C14 was injected 24 hours prior to BAPN, the specific radioactivity of the soluble collagen of treated embryos was similar to that of controls, in spite of the fact that the specific activity of the residue fraction was higher than that of the soluble fraction at the time of BAPN administration.

These results suggest that the increased amount of soluble collagen in lathyrism induced by administration of BAPN does not arise from the collagen insoluble prior to administration of the drug, but rather that BAPN acts by blocking the formation of mature collagen fibers, perhaps by preventing the formation of cross-linkages between α-collagen chains.

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