| Grant number: | 13/17410-7 |
| Support Opportunities: | Scholarships in Brazil - Doctorate |
| Start date until: | January 01, 2014 |
| End date until: | December 31, 2017 |
| Field of knowledge: | Biological Sciences - Physiology - Compared Physiology |
| Principal Investigator: | Ana Lúcia Kalinin |
| Grantee: | Rafael Zanelli Rissoli |
| Host Institution: | Centro de Ciências Biológicas e da Saúde (CCBS). Universidade Federal de São Carlos (UFSCAR). São Carlos , SP, Brazil |
Abstract The sequence of events since the sarcolemma depolarization until the force generation by the myofilaments is called excitation-contraction (E-C) coupling. The autonomic action of a group of pacemaker cells generates action potentials which, reaching the myocytes, can drive a small intracellular Ca2+ influx by the activation of L-type channels and Na+/Ca+ exchangers (NCX) and initiate the cardiac contraction processes. Most endothermic vertebrates presents the major fraction of intracellular Ca2+ stocked inside the sarcoplasmic reticulum (SR) and the contraction is promoted mainly by SR calcium release, which is triggered when the small extracellular influx binds to SR ryanodine receptors (RyR). Afterwards, the relaxation occurs due to the activity of a SR Ca2+-ATPase (SERCA2a) by the phosphorylation of phospholamban (PLB), a protein present on RS membrane, and the small amount of extracellular Ca2+ is removed by NCX and the sarcolemmal Ca2+-ATPase. Ectothermic vertebrates, however, present more heterogenic E-C coupling mechanisms. In several ectothermic species, the extracellular Ca2+ influx is enough to activate the myocyte contraction without a significant participation of the SR. On the other hand, in some fish species, an important role of the SR in Ca2+ supplying have been reported, particularly in species with a high activity level. In spite of these interspecific differences, there is a huge plasticity in the E-C coupling in respond to high cardiac function demands, such as during long exercise periods. The molecular analysis of the heart muscle of mice and rats submit to daily aerobic exercises indicated a clear elevation in the transcription of L-channels, SERCA2a, PLB and RyR channels. Despite the considerable number of studies describing some of mechanisms involved in the heart adaptation to extended exercise in some fish species, such as changes in the maximum cardiac output, hematocrit, tissue capillarization, and relative cardiac mass, there are few data regarding to the effect of the exercise training on the capacity of the cardiac contractile machinery to produce force. A recent study indicated that the Atlantic salmon (Salmo salar) increases the E-C coupling efficiency when submitted to 10 weeks of continuous exercise, presenting an increased expression of genes related to the Ca2+ management proteins. Matrinxã (Brycon amazonicus) is rightfully an athletic species, native of the Amazon river basin, presenting several migratory events during its life circle. Previous studies demonstrated that ventricular myocardium of this species is highly dependent on RS Ca2+ release to produces force, which was corroborated by the expression of SERCA2a and PLB in this tissue. Therefore, the goal of the present study is to investigate the effects of extensive exercise on the in vitro cardiac contractility in sedentary and exercise-trained specimens of matrinxã, emphasizing the role of each component of the E-C coupling by means of the protein expression. (AU) | |
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