Heterogeneity of smooth muscle in bovine coronary arteries.

The monoclonal antibodies TT-1 against troponin T and TI-1 against troponin I of cardiac muscle, together with Western blots and immunofluorescence techniques, were used to evaluate the presence of troponin-like antigens in the smooth muscle cells of bovine coronary arteries. The walls of the left coronary artery before the bifurcation, its circumflex and descending branches, the right coronary artery, and the small branches of coronary arteries and the intramural arterial vessels were found to be homogeneously stained by the TT-1 antibody. Conversely, with the TI-1 antibody, differences were observed in the distribution of the TnI-like antigen among the smooth muscle cells of extramural and intramural vessels. Heterogeneity of the smooth muscle cells of the coronary artery was also evident in the medial layer of large vessels near the branching points, where an intimal thickening was consistently observed. Double immunofluorescence assays with anti-troponin antibodies in vivo and in vitro indicated a distinct intracellular localization of troponin T and troponin I immunoreactivities in vascular smooth muscle cells. The data are compatible with the existence of distinct troponin-like antigens in smooth muscle cells of bovine coronary arteries whose distribution is in part related to the extramural or intramural localization of blood vessels.