Longitudinal sections of adult rat EDL were immunolabeled with specific antibodies against Ca2+-ATPase and Trisk 49 (panels a, b and c), desmin and Trisk 49 (panels d, e and f), and titin and Trisk 49 (panels g, h and i). Ca2+-ATPase is a longitudinal sarcoplasmic reticulum marker, desmin labels the Z-line, and antibodies used against titin are specific to the A-I interface.