Aortic smooth muscle cells contain vimentin instead of desmin

The 10-nm filament subunit proteins of smooth muscle cells in the mammalian aorta were analyzed by immunofluorescence and by two-dimensional gel electrophoresis. Indirect immunofluorescence studies on frozen sections of aorta showed intense staining of the tunica media by antibodies to vimentin, whereas no reaction could be detected with antibodies to desmin. Crude preparations from the tunica media contain a protein with molecular weight and isoelectric point similar to those of vimentin. Desmin was not detected on these same two-dimensional gels. We conclude that aortic smooth muscle cells contain vimentin as the predominant form of 10-nm filament protein subunit, unlike other muscle cells in which desmin predominates. Other immunofluorescence results indicate that the aorta may differ from smaller blood vessels which appear to contain both desmin and vimentin.