Submitted on September 10, 2008
Revised on May 21, 2009
Accepted on May 26, 2009
Exercise capacity is related to calcium transients in ventricular cardiomyocytes
Thales N. Primola-Gomes1, Lúcia Aparecida Campos1, Sandra Lauton-Santos2, Cláudio Heitor Balthazar3, Silvia Guatimosim1, Luciano S.A. Capettini1, Virginia Soares Lemos1, Cândido Celso Coimbra1, Danusa Dias Soares1, Miguel Araújo Carneiro Júnior4, Judson Fonseca Quintão Júnior4, Matheus Ornelas Souza4, Jader S. Cruz5, and Antonio José Natali4*
1 Federal University of Minas Gerais
2 Federal University of Sergipe
3 Institute of Biological Sciences, Federal University of Minas Gerais
4 Federal University of Viçosa
5 Universidade Federal de Minas Gerais
* To whom correspondence should be addressed. E-mail: anatali{at}ufv.br.
The aim of the present study was to evaluate the Ca2+ handling and contractility properties of cardiomyocytes isolated from rats with high intrinsic aerobic exercise capacity. Standard performance (SP) and high performance (HP) rats were categorized with a treadmill progressive exercise test according to the exercise time to fatigue (TTF). The SP group included rats with TTF between 16.63-46.57 min and the HP group included rats with TTF >46.57 min. Isolated ventricular cardiomyocytes were dissociated from the hearts of SP and HP rats, and intracellular global Ca2+ [Ca2+]i transients were measured. The [Ca2+]i transient peak was increased in the HP group relative to SP (5.54 ± 0.31 vs. 4.18 ± 0.12 F/F0; P
0.05) and was positively correlated with the TTF attained during the progressive test (r = 0.81). We also performed contractility measurements in isolated cardiomyocytes and found higher amplitude of contraction in the HP group when compared to SP (6.7 ± 0.2 vs. 6.0 ± 0.3 %r.c.l.; P 0.05). To reinforce the intrinsic differences between SP and HP rats, we performed Western Blot experiments and observed increased expression of SERCA2a (1.30 ± 0.07 vs. 1.74 ± 0.18 arbitrary units; P 0.05) and RyR2 (1.86 ± 0.13 vs. 3.57 ± 0.12 arbitrary units; P 0.05) in HP rats. In summary, our data showed important intrinsic differences in cardiomyocyte properties that could explain some of the divergence observed in rats with high intrinsic aerobic exercise capacity.
