Synthesis of elastin. A rapid formation of lysine-derived crosslinks by chick embryo aorta.

Aortas of 13-day-old chick embryo were labeled for 0.5 hr with [14C]lysine and subjected to a serial extraction after chase for 1-24 hr with [12C]lysine. Substantial radioactivity was found in insoluble elastin after 3 hr chase. The effect of beta-amino-propionitrile on labeling with [14C]lysine was also examined. Each fraction was hydrolyzed and applied to a short column on an amino acid analyzer. Radioactivity was found in desmosine and isodesmosine of insoluble elastin as early as 1 hr after the beginning of chase. The radioactivity increased rapidly at 2 hr and very slowly thereafter. A large count, which was separated into five peaks on a long column, was observed in other lysine derivatives at 2 hr and increased steadily up to 24 hr, while the lysine count decreased from 1 : 0.5 to 1 : 6 against lysine derivatives and from 1 : 0.04 to 1 : 0.9 against quarter-desmosine after 24 hr. The oxidation of lysine residues incorporated during the 0.5 hr pulse was almost completed during the first 1 hr of chase, and these oxidized residues were incorporated into crosslinks during the following 1 hr. It is suggested that poorly crosslinked elastin accumulated in the soluble fractions. The presence of crosslinking derived from lysine residues was also indicated in the microfibril fraction.