Elevation of histidinoalanine in calcified human aortas.

The cross-links histidinoalanine (HA); pyridinoline (Pyr); desmosine (Des); and isodesmosine (Ides) in human atherosclerotic aortas were studied. Only HA showed a significant increase in calcified aortas, with a high concentration in the insoluble "mineralized" fraction, which was separated out after treatment of tissues with pronase E. The cross-links composition was similar among "mineralized" fractions prepared from tissues of varying degrees of calcification: values were 2.40; 0.10; 0.17; and 0.16 moles per 1000 moles of amino acid residues for HA; Pyr; Des; and Ides, respectively. The findings suggest that the HA-containing peptide may play an important role in the calcification process of aortic tissues.