Costameres are sites of force transmission to the substratum in adult rat cardiomyocytes

A technique combining the flexible silicone rubber substratum technique with microinjection of fluorescent-labeled alpha-actinin and actinin was developed to test the hypothesis that costameres provide mechanical linkage between muscle cell contractile machinery and the extracellular matrix. The results showed that the distribution of vinculin-rich costameres are correlated with the patterns of forces exerted by adult rat cardiac myocytes on the flexible substrate. Furthermore, it is suggested that costameres can transmit forces to the extracellular matrix based on the observed relation of the cells with its underlying substrate as shown by interference electron microscopy.