title: The benefits of endurance training in cardiomyocyte function in hypertensive rats are reversed within four weeks of detraining.
abstract: The aim of the present study was to verify the effects of low-intensity endurance training and detraining on the mechanical and molecular properties of cardiomyocytes from spontaneously hypertensive rats (SHRs). Male SHRs and normotensive control Wistar rats at 16-weeks of age were randomly divided into eight groups of eight animals: NC8 and HC8 (normotensive and hypertensive control for 8weeks); NT8 and HT8 (normotensive and hypertensive trained at 50-60% of maximal exercise capacity for 8weeks); NC12 and HC12 (normotensive and hypertensive control for 12weeks); NDT and HDT (normotensive and hypertensive trained for 8weeks and detrained for 4weeks). The total exercise time until fatigue (TTF) was determined by a maximal exercise capacity test. Resting heart rate (RHR) and systolic arterial pressure (SAP) were measured. After the treatments, animals were killed by cervical dislocation and left ventricular myocytes were isolated by enzymatic dispersion. Isolated cells were used to determine intracellular global Ca(2+) ([Ca(2+)]i) transient and cardiomyocyte contractility (1Hz; ~25°C). [Ca(2+)]i regulatory proteins were measured by Western blot, and the markers of pathologic cardiac hypertrophy by quantitative real-time polymerase chain reaction (q-RT-PCR). Exercise training augmented the TTF (NC8, 11.4±1.5min vs. NT8, 22.5±1.4min; HC8, 11.7±1.4min vs. HT8, 24.5±1.3min; P<0.05), reduced RHR (NT8initial, 340±8bpm vs. NT8final, 322±10bpm; HT8initial, 369±8bpm vs. HT8final, 344±10bpm; P<0.05), and SBP in SHR animals (HC8, 178±3mmHg vs. HT8, 161±4mmHg; P<0.05). HC8 rats showed a slower [Ca(2+)]i transient (Tpeak, 83.7±1.8ms vs. 71.7±2.4ms; T50%decay, 284.0±4.3ms vs. 264.0±4.1ms; P<0.05) and cell contractility (Vshortening, 86.1±6.7μm/s vs. 118.6±6.7μm/s; Vrelengthening, 57.5±7.4μm/s vs. 101.3±7.4μm/s; P<0.05), and higher expression of ANF (300%; P<0.05), skeletal α-actin (250%; P<0.05) and a decreased α/β-MHC ratio (70%; P<0.05) compared to NC8. Exercise training increased [Ca(2+)]i transient (NC8, 2.39±0.06F/F0 vs. NT8, 2.72±0.06F/F0; HC8, 2.28±0.05F/F0 vs. HT8, 2.82±0.05F/F0; P<0.05), and cell contractility (NC8, 7.4±0.3% vs. NT8, 8.4±0.3%; HC8, 6.8±0.3% vs. HT8, 7.8±0.3%; P<0.05). Furthermore, exercise normalized the expression of ANF, skeletal α-actin, and the α/β-MHC ratio in HT8 rats, augmented the expression of SERCA2a (NC8, 0.93±0.15 vs. NT8, 1.49±0.14; HC8, 0.83±0.13 vs. HT8, 1.32±0.14; P<0.05) and PLBser16 (NC8, 0.89±0.18 vs. NT8, 1.23±0.17; HC8, 0.77±0.17 vs. HT8, 1.32±0.16; P<0.05), and reduced PLBt/SERCA2a (NC8, 1.21±0.19 vs. NT8, 0.50±0.21; HC8, 1.38±0.17 vs. HT8, 0.66±0.21; P<0.05). However, all these adaptations returned to control values within 4weeks of detraining in both SHR and normotensive control animals. In conclusion, low-intensity endurance training induces positive benefits to left ventricular myocyte mechanical and molecular properties, which are reversed within 4weeks of detraining.
authors: Department of Physiological Sciences, Federal University of Espírito Santo (UFES), Vitória, Espírito Santo, Brazil.
authors: Miguel Araujo
authors: MA
authors: Carneiro-Júnior
authors: Judson Fonseca
authors: JF
authors: Quintão-Júnior
authors: Lucas Rios
authors: LR
authors: Drummond
authors: Victor Neiva
authors: VN
authors: Lavorato
authors: Filipe Rios
authors: FR
authors: Drummond
authors: Daise Nunes Queiroz
authors: DN
authors: da Cunha
authors: Marco Aurélio
authors: MA
authors: Amadeu
authors: Leonardo Bonato
authors: LB
authors: Felix
authors: Edilamar Menezes
authors: EM
authors: de Oliveira
authors: Jader Santos
authors: JS
authors: Cruz
authors: Thales Nicolau
authors: TN
authors: Prímola-Gomes
authors: José Geraldo
authors: JG
authors: Mill
authors: Antonio José
authors: AJ
authors: Natali
mesh_terms: D000818:Animals; D009320:Atrial Natriuretic Factor / Q000235:genetics / Q000378:metabolism; D020013:Calcium Signaling; D002135:Calcium-Binding Proteins / Q000235:genetics / Q000378:metabolism; D002478:Cells, Cultured; D005081:Exercise Therapy; D015870:Gene Expression; D006352:Heart Ventricles / Q000378:metabolism / Q000503:physiopathology; D006973:Hypertension / Q000378:metabolism / Q000503:physiopathology / Q000628:therapy*; D017379:Hypertrophy, Left Ventricular / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology; D008297:Male; D009200:Myocardial Contraction; D032383:Myocytes, Cardiac / Q000502:physiology*; D018995:Myosin Heavy Chains / Q000378:metabolism; D010805:Physical Conditioning, Animal; D010807:Physical Endurance; D051381:Rats; D011918:Rats, Inbred SHR; D017208:Rats, Wistar; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000235:genetics / Q000378:metabolism; D000099211:Phospholamban
chemical_list: D009320:Atrial Natriuretic Factor; D002135:Calcium-Binding Proteins; D018995:Myosin Heavy Chains; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D000099211:Phospholamban