Physical Exercise and Regulation of Intracellular Calcium in Cardiomyocytes of Hypertensive Rats

BACKGROUND: Regulation of intracellular calcium (Ca(2+)) in cardiomyocytes is altered by hypertension; and aerobic exercise brings benefits to hypertensive individuals. OBJECTIVE: To verify the effects of aerobic exercise training on contractility and intracellular calcium (Ca(2+)) transients of cardiomyocytes and on the expression of microRNA 214 (miR-214) in the left ventricle of spontaneously hypertensive rats (SHR). METHODS: SHR and normotensive Wistar rats of 16 weeks were divided into 4 groups -sedentary hypertensive (SH); trained hypertensive (TH); sedentary normotensive (SN); and trained normotensive (TN). Animals of the TH and TN groups were subjected to treadmill running program, 5 days/week, 1 hour/day at 60-70% of maximum running velocity for 8 weeks. We adopted a p ≤ 0.05 as significance level for all comparisons. RESULTS: Exercise training reduced systolic arterial pressure in hypertensive rats. In normotensive rats, exercise training reduced the time to 50% cell relaxation and the time to peak contraction and increased the time to 50% decay of the intracellular Ca(2+) transients. In SHR, exercise increased the amplitude and reduced the time to 50% decay of Ca(2+) transients. Exercise training increased the expression of miR-214 in hypertensive rats only. CONCLUSION: The aerobic training applied in this study increased the availability of intracellular Ca(2+) and accelerated the sequestration of these ions in left ventricular myocytes of hypertensive rats, despite increased expression of miR-214 and maintenance of cell contractility.