Expression of the Na-Ca exchanger (NCX), the majer myocyte Ca2+ extrusion pathway during diastole, has been shown to be sensitive to increases in hemodynamic load during cardiac hypertrophy. In this study, we examined the effect of exercise training on myocardial NCX activity and expressed protein levels in porcine cardiac sarcolemmal (SL) vesicles. Miniature Yucatan swine (male) were exercised trained (EX) on a motor-driven treadmill or maintained sedentary (SED) for 16-22 weeks. Following euthanization and removal of hearts, cardiac SL vesicles were prepared from ventricular tissue. Initial NCX transport rates (at 12 μM Ca) for EX (n=2) and SED (n=2) were 1.13 ±0.15 and 1.08 ±0.12 nmol Ca/mg prot/sec (SE) , respectively. Kinetic analysis of Ca2+ transport yielded a Km of 28 μM (EX) and 26 μM (SED) and a Vmax of 2.4 nmol Ca/mg prot./sec (EX and SED). Western blot analysis of EX and SED SL vesicles by a commercial monoclonal antibody and a site-directed polyclonal antibody against the XIP domain of the NCX protein showed no difference in levels of exchanger protein. We conclude that exercise training does not alter the activity or the apparent expressed levels of NCX in porcine cardiac SL vesicles. As NCX activity is sensitive to changes in the SL phospholipid environment, these results suggest that exercise training does not alter the SL phospholipid composition.
|Original language||English (US)|
|State||Published - Dec 1 1997|
ASJC Scopus subject areas
- Molecular Biology