Effects of chronic hypoxia on the developmental changes in action potential of cultured neonatal rat ventricular myocytes.
The action potentials of rat ventricular myocytes are known to become progressively shortened within several weeks after birth. We studied the effects of long-term exposure to hypoxia on these developmental changes in cardiac action potentials. Single ventricular myocytes isolated from day-old neonatal rat hearts were cultured in normoxic conditions (21% O2) for more than 15 days. To test the influence of long-term exposure to hypoxia, O2 tension was lowered to 7.5% in some cells at day 6. Action potentials were measured at day 5 and day 15 in both the normoxic and hypoxic groups. Under normoxic conditions, action potential durations decreased by 44% between day 5 and day 15, while cell capacitance doubled (n=10-11). Under hypoxic conditions, action potential durations decreased slightly by 16% (n=6). This shortening was significantly attenuated when compared to that observed during normoxic conditions. Cell capacitance was not altered under the hypoxic conditions. These results suggest that 1) shortening of the action potential during normoxic culturing is prevented under hypoxic conditions, and 2) cell capacitance as seen in normoxic conditions is unaffected by hypoxic culturing.
Kamiya
K
K
Department of Circulation, Division of Regulation of Organ Function, Research Institute of Environmental Medicine, Nagoya University, Nagoya, Japan.
Guo
W
W
Toyama
J
J
D000200:Action Potentials; D000818:Animals; D000831:Animals, Newborn; D015687:Cell Hypoxia / Q000502:physiology; D002478:Cells, Cultured; D000860:Hypoxia / Q000503:physiopathology*; D032383:Myocytes, Cardiac / Q000166:cytology / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar