Figure 3.

WB F344 myocytes express cardiac-specific protein. Undifferentiated WB F344 cells and WB F344-derived myocytes express β-galactosidase (blue cells in a–d). WB F344-derived cardiomyocytes co-express cardiac myosin, striated red fluorescence in a, 2 and 3 (13 days co-culture); cardiac-specific cTnI, red fluorescence in b (13 days co-culture); cardiac-specific cTnT, striated red fluorescence in c (7 days co-culture); connexin 43, green fluorescence in d (13 days co-culture). Select confocal microscopic stacks in a and b demonstrate that neonatal myocytes do not overlie or underlie the WB F344-derived myocytes. Expression of myosin and TnI is inherent to the WB F344-derived myocytes that co-express β-galactosidase. Undifferentiated WB F344 cells are predominant in the 13-day co-cultures (a and b). Arrow in a3 depicts the nucleus of a neonatal cardiomyocyte. Arrow in a7 depicts the body of the same neonatal cardiomyocyte in contact with the WB F344-derived myocyte. The distribution of connexin 43 throughout the WB F344-derived myocyte cell membranes (d) is consistent with the immaturity of the myocyte. The arrow at the top in d represents connexin 43 expression in an adjacent neonatal cardiac myocyte that does not express β-galactosidase. Original magnifications, ×40.