Fig. 8. Proepicardial cells are functionally coupled by gap junctions. Single cells in a wild-type (A) and a Cx431 knockout (C) proepicardial explant culture were impaled with a microelectrode (arrow) and iontophoretically injected with carboxyfluorescein. The gap junction mediated spread of carboxyfluoescein to adjacent cells can be seen in the darkfield images of a wild-type PEO explant (B), but not in a Cx431 knockout explant (D). Scale bar: 60 µm.