Variation in proteins of single lesions from the intima of the aorta from a human patient with severe atherosclerosis

Abstract

A method is presented for grinding and extracting very small samples of tough fibrous tissue from single atherosclerotic lesions of human aortas. Grinding to a powder was easily accomplished while the samples were frozen in liquid nitrogen in a porcelain micromortar. Extractions of the powder were made first in the mortar and then in tapered centrifuge tubes. Salt soluble, dodecyl sulfatemercaptoethanol-urea soluble and hot alkali soluble fractions were obtained, in addition to a hot alkali insoluble elastin residue from each sample. Variation in the protein composition of 23 samples from the lumenal surface of the severely atherosclerotic aorta of a 58-year-old human male were determined. The proteins soluble in the buffered-saline and the dodecyl sulfate—urea soluble polypeptides from each sample were analyzed by dodecyl sulfate—acrylamide gel electrophoresis. The amino acid compositions of the insoluble elastin fractions were determined. The 5 grossly normal intima samples had very similar gel electrophoresis band patterns and amino acid compositions. The 3 samples of necrotic gruel had markedly different dodecyl sulfate—urea soluble polypeptides than either normal or calcified tissue; they also had elastin fractions whose amino acid compositions were unique in that they contained 10 times more serine than elastin fractions from grossly normal intima. The 3 calcified samples had less saline or dodecyl sulfate soluble protein than either grossly normal or necrotic gruel samples, and had very altered elastin fraction compositions characterized by much higher contents of hydroxylysine than grossly normal intima. The elastin fractions of necrotic gruel and calcified tissue samples had little or no isodesmosine or desmosine, suggesting that little of the elastin found in healthy aorta tissue was present.