Figure 10.

Ultrastructural changes of the intercalated disk after volume overload. The control shows thin and flat disks with short interdigitations (1/4- to 1/3-sarcomere long) (A [Control]) (I-mode). At 6 hours of volume-overload, the ICD becomes thick with one-sarcomere-long interdigitations (B [6 hours]) (II-mode). At 12 hours, the ICD is folded to form ∼one-sarcomere-deep grooves (G) and contra-grooves (G) with short interdigitations (C [12 hours]) (III-mode). At 1 day, interdigitations elongate up to one sarcomere long in the folded ICD (D [1 day]) (IV-mode) so that the ICD broadens to ∼two sarcomeres wide. Grooves (G) and contra-grooves (G) appear in this mode. At 1.5 days, the ICD is thin with mostly short interdigitations, but one-sarcomere-long interdigitations sporadically appear as spikes (E [1.5 days]) (V-mode). There appear “spaces” (S) surrounded by several spikes. At 2 days, the ICD is thin and flat with short interdigitations similar to those of controls, finishing one cycle of ICD changes during volume overload (F [2 days]) (I-mode). Longitudinal section to myocytes.