Modulation of potassium channels by chronic hypoxia in neonatal rat cultured ventricular myocytes

We studied the effects of long-term exposure to hypoxia on the developmental change of transient outward current (Ito) in neonatal rat cultured ventricular myocytes. Ventricular myocytes of day-old neonatal rat hearts were cultured in normoxic condition (21%, O2) for 15 days. Some cells were cultured at lower O2 concentration of 7.5% from day 6 to day 15. During 6-15 days of cultivation in normoxic condition, a two to three fold increase (n=11-12) in Ito density was observed without changes in the kinetics of current inactivation. In the hypoxic condition during the same culture period, the developmental increment in Ito was reduced to 53% (n=8) and was characterized by slow kinetics of the inactivation process. These results suggest that the development of Ito is influenced by the oxygen concentration, and that the remarkable increase in Ito after birth may result from an elevation in blood oxygen concentration during the perinatal period.