[Incorporation of L-azetidine-2-carboxylic acid into collagen of the skin. Structural changes]

As previously shown by two dimensional thin-layer chromatography L-azetidine-2-carboxylic-acid (L-Az) is incorporated into type I skin collagen instead of proline when 3 week old mice are fed with a 0,1% solution of L-Az orally. Ultrastructural investigations did not reveal significant changes in collagen periodicity and on fibril diameter. The collagen fibrils of the upper papillary dermis seemed to be packed more densely, sometimes only one electron dense lamina was seen instead of basal lamina and plasma membrane. The glycosaminoglycane-induced fibrillogenesis was not changed in contrary to the collagen-heat-gelation fibrillogenesis at 37 degrees C, where no gel aggregation could be seen. The reconstruction of native fibres from collagen solutions was disturbed too, several finer precipitated fibrils being detectable. On infrared spectroscopy significant differences in absorption spectra were detected. Correlating with previous results of reduced tensile strength and normal melting point of L-Az collagen we can conclude that L-Az might cause rather intermolecular than intramolecular disturbances of crosslinking.