Na/Ca exchanger‐1 mediates hypertrophy of cultured neonatal mouse cardiomyocytes in chronic intermittent hypoxia

Abstract

Cardiac‐specific Na/Ca exchanger‐1 (NCX1) knockout (KO) mice is resistant to chronic intermittent hypoxia (CIH)‐induced cardiac hypertrophy in vivo (Chen et al. J Appl Physiol 2010; 109:1675). We studied the effect of CIH on NCX protein expression and cell size in primary cultured neonatal cardiomyocytes from either wild type (WT) or KO mice. CIH was produced by introducing mixed gases containing 0% or 21% O2 at a periodicity of 20 and 20 min, which achieved a nadir pO2 10 and peak 120 mmHg at the bottom of culture media. Daily exposure for CIH included 12h CIH, followed by 12h 21% O2. Control cells were cultured only in 21% O2. At the end of 5‐day exposure, WT with CIH had significantly greater NCX protein expression (~60%) and cell cross sectional area (1158 ± 181 vs 856 ± 98 μm2, P < 0.05) compared to WT control. Cell area in KO with CIH was 917 ± 138 μm2, which is significantly smaller than in WT with CIH (P< 0.05), but not significantly different from either WT or KO controls. NCX protein expression was not significantly different between KO groups, which are ~25% of that in WT control.ConclusionNCX1 mediates cell hypertrophy in cultured neonatal cardiomyocytes following CIH exposure.