Renal hypertension prevents run training modification of cardiomyocyte diastolic Ca regulation in male rats

Palmer, Bradley M., Joshua M. Lynch, Steven M. Snyder, and Russell L. Moore. Renal hypertension prevents run training modification of cardiomyocyte diastolic Ca21 regulation in male rats. J Appl Physiol 90: 2063–2069, 2001.—The combined effects of endurance run training and renal hypertension on cytosolic Ca21 concentration ([Ca]c) dynamics and Na-dependent Ca21 regulation in rat left ventricular cardiomyocytes were examined. Male Fischer 344 rats underwent stenosis of the left renal artery [hypertensive (Ht), n 5 18] or a sham operation [normotensive (Nt), n 5 20]. One-half of the rats from each group were treadmill trained for .16 wk. Cardiomyocyte fura 2 fluorescence ratio transients were recorded for 7 min during electrical pacing at 0.5 Hz, 2 mM extracellular Ca21 concentration, and 29°C. The rate of [Ca]c decline was not changed by run training in the Nt group but was reduced in the Ht group. At 7 min, cardiomyocytes were exposed to 10 mM caffeine in the absence of Na and Ca21, which triggered sarcoplasmic reticular Ca21 release and suppressed Ca21 efflux via Na1/Ca21 exchanger. External Na was then added, and Na-dependent Ca21 efflux rate was recorded. Treadmill training significantly enhanced Na-dependent Ca21 efflux rate under these conditions in the Nt group but not in the Ht group. These data provide evidence that renal hypertension prevents the normal run training-induced modifications in diastolic [Ca]c regulation mechanisms, including Na1/Ca21 exchanger.