Fibronectin penetration into heart myocytes subjected to experimental ischemia by coronary artery ligation

Using confocal microscopy and immunocytochemistry we have studied early changes in distribution of fibronectin (FN) in myocardial cells of rats subjected to experimental acute myocardial ischemia (AMI) by coronary ligation for several periods of 0.5 h to 6 days. In sham-operated and nonoperated rats, FN was present in the interstitium around the myocytes, and in their transverse tubules (TT). Already after 0.5 h of ischemia there was a well-defined increase of immunoreactive FN in focal areas of the interstitium of the hypoperfused portion, and distinct penetration into adjacent myocytes. The early penetration of FN into myocytes appears to follow a path through the TT, with a codistribution with actin in the I bands. This process precedes a total and diffuse infiltration of FN into the cytoplasm of disintegrating myocytes at later stages of coronary occlusion.