Dihydropyridine precursors of elastin crosslinks

Dihydrodesmosine and dihydroisodemosine are dihydropyridines which are believed to be the immediate biosynthetic precursors of desmosine and isodesmosine, the stable pyridinium ion crosslinks of elastin. It has recently been reported that appreciably amounts of dihydrodesmosine and dihydroisodesmosine accumulate in elastin. In view of the ease with which such dihydropyridines are oxidized to the corresponding pyridinium ions by O2 and other mild oxidants, dihydrodesmosine and dihydroisodesmosine would not be expected to accumulate in elastic tissues. It therefore seemed appropriate to analyse elastin samples for dihydrodesmosine and dihydroisodesmosine using techniques different from these previously employed for this purpose. The results of these investigations indicate that dihydrodesmosine and dihydroisodesmosine do not accumulate to a measurable extent in elastin.