Figure 3.

Fetal remodeled but not hypertrophic cardiomyocytes show MAPK dependent ischemic resistance. Primary cultures of adult cardiomyocytes were untreated (Con) or treated with isoproterenol (ISO), serum (Serum), and morphogens (Morpho) for 6 days. Cardiomyocytes were seeded at low density except in (C). UO126 (5 µM) was added (+UO) 1 h before experimental start. Note that cultures were pretreated with siRNA (siCon, siBRaf) three days before experimental start. Single and double stars indicate p < 0.01 and p < 0.001, respectively. Hash signs indicate p < 0.05. Black signs refer statistically to the 0 d group, blue signs to serum, and red compares Morpho (Morpho, Morpho siCon) statistically with and without UO/siB-Raf (+UO, siBRaf). The green star refers to the siCon group. (A) Phase-contrast images of cardiomyocyte cultures. (B) Quantitative and statistical evaluation of cell length and diameter of (A). (C) Total protein content of 6 d-treated cultures at high cell density were compared with cardiomyocytes at experimental start (0 d). (D) Cardiomyocytes were pretreated for 6 days with 0.2 mg/mL albumin (Con), serum, serum + UO126, morphogen, morphogen + UO126. At the end of a 6-day culture period, all cells were counted (reference value 100%) and then kept in glucose-free PBS at 1% O₂. After 9 h of ischemia, cardiomyocytes were fixed in 4% paraformaldehyde and recounted.