HETEROGENEITY OF SMOOTH-MUSCLE IN BOVINE CORONARY-ARTERIES

The monoclonal antibodies TT-1 against troponin T and TI-1 against tro ponin I of cardiac muscle, together with Western blots and immunofluor escence techniques, were used to evaluate the presence of troponin-lik e antigens in the smooth muscle cells of bovine coronary arteries. The walls of the left coronary artery before the bifurcation, its circumf lex 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, w ith the TI-1 antibody, differences were observed in the distribution o f the TnI-like antigen among the smooth muscle cells of extramural and intramural vessels. Heterogeneity of the smooth muscle cells of the c oronary artery was also evident in the medial layer of large vessels n ear the branching points, where an intimal thickening was consistently observed. Double immunofluorescence assays with anti-troponin antibod ies in vivo and in vitro indicated a distinct intracellular localizati on of troponin T and troponin I immunoreactivities in vascular smooth muscle cells. The data are compatible with the existence of distinct t roponin-like antigens in smooth muscle cells of bovine coronary arteri es whose distribution is in part related to the extramural or intramur al localization of blood vessels.