Fig. 2. Effects of moderate, substrate-free hypoxia on ventricular action potential duration (APD) in the isolated goldfish heart. APD in hypoxia was significantly shortened at 90% of full repolarization, but not at 50% (N=5). Inset shows representative action potential configuration in one experiment (normoxia at left). Values are means ± 1 S.E.M. **Significantly different from values recorded under normoxic conditions (P<0.01).