Octávio Barbosa Neto

O bloqueio da síntese do óxido nítrico promove aumento da hipertrofia e da fibrose cardíaca em ratos submetidos a treinamento aeróbio

Summary Objective: The objective of the present study was to evaluate cardiac tissue adaptations in rats submitted to aerobic training after nitric oxide (NO) synthesis blockade. Methods: The animals (n=48) were divided into four groups: sedentary (CONTROL group); hypertensive after administration of NG-nitro-Larginine methyl ester for 7 days (L-NAME Group); trained for 8 weeks through swimming exercises (TRAINED Group);trained and treated with L-NAME during the last week (L-NAME TRAINED Group). All the animals were submitted to the experiment procedures for blood pressure (BP) readings and cardiac morphometric evaluation. Results: In comparison to the other groups, the L-NAME and L-NAME TRAINED groups were hypertensive (p<0.05); however, BP elevation in the L-NAME TRAINED group was significantly lower than the L-NAME group (p<0.05). The heart weight indexes for the TRAINED and L-NAME TRAINED groups were higher than the CONTROL and L-NAME groups (p<0.05). Also they had presented higher rates of macroscopic cardiac area and cardiac fibrosis in relation to the rest (p<0.05); comparisons revealed that the values for the L-NAME TRAINED group were significantly higher (p<0.05) than the others. Conclusion: Short term NO synthesis blockade in sedentary animals induced hypertension but did not cause cardiac hypertrophy. In the trained animals, the inhibition of NO synthesis attenuated hypertension, induced cardiac hypertrophy and significantly increased myocardial fibrosis, indicating that NO plays an important role in cardiac tissue adaptations caused by aerobic exercise. (Arq Bras Cardiol 2007;89(2):88-93)

Exercise-Training Reduced Blood Pressure and Improve Placental Vascularization in Pregnant Spontaneously Hypertensive Rats –Pilot Study

Assess the effects of exercise-training on resting arterial pressure and heart rate, placental fetuses morphologic alterations in pregnant spontaneously hypertensive rats (SHRs).Twenty SHRs and their respective control normotensive rats (WKY) were submitted or not to a swimming protocol during 9 weeks, resulting in four pregnant experimental groups: sedentary hypertensive (PSH), trained hypertensive (PTH), sedentary normotensive (PSN), and trained normotensive (PTN). Exercise-training by swimming attenuates arterial pressure in pregnant SHRs, and can contribute to an increase in the length of fetuses and the percentage of the vessels in the placenta.

ACUTE RESPONSES OF RATE PRESSURE PRODUCT IN SETS OF RESISTANCE EXERCISE

Objective: To compare the acute responses of rate pressure product (RPP) between dynamic and isometric sets of resistance exercise (RE); compare the acute responses of RPP between upper and lower limbs in RE. Methods: Nineteen active men (22.7 ± 2.2 years) attended this study in a random crossover model. In the first day they performed hemodynamic measurements and one maximum repetition tests (1RM) in leg press (LGP) and bench press (BCP) exercises. In the second, third, fourth and fifth days they performed the following tests: LGP isometric, BCP isometric, LGP dynamic and BCP dynamic, respectively. Isometric protocols were conducted in 3 sets of 40 s (1 st set: 25% 1RM, 2 nd set: 50% 1RM, 3 rd set: 75% 1RM) and dynamic protocols in 3 sets of 10 repetitions (1 st set: 25% 1RM, 2 nd set: 50% 1RM, 3 th set: 75% 1RM). The RPP was obtained immediately after each set. Results: A comparison between protocols showed that RPP was higher (P < 0.05) in dynamic than in isometric protocol. A comparison between exercises showed that RPP was higher (P < 0.05) in LGP than BCP exercise. Conclusions: In similar relative intensities, the acute cardiac responses are influenced by the exercise protocol, since the RPP was higher in the dynamic condition. Furthermore, RPP seems to be related with recruited muscle mass, since that were observed higher values of RPP in exercises for lower limbs .

Exercise training improves hypertension-induced autonomic dysfunction without influencing properties of peripheral cardiac vagus nerve

We examined the vagal transfer function of autonomic heart rate (HR) control in anesthetized sedentary and exercise-trained Spontaneously Hypertensive Rats (SHR). To this end, male SHR and Wystar-Kyoto (WKY) rats with 48-50weeks of age-old were divided into 4 groups: sedentary (SHRS, n=12) and trained (SHRT, n=14) hypertensive rats, sedentary (WKYS, n=13) and trained (WKYT, n=13) normotensive rats. The trained groups were submitted to swimming protocol for 9weeks. Blood pressure (BP), HR, HR variability (HRV), BP variability (BPV), baroreflex sensitivity and cardiac tonus were recorded in baseline conditions. Following, electric stimulation of peripheral vagus nerve was performed in anesthetized conditions. Resting bradycardia was observed in SHRT and WKYT when compared to their respective sedentary groups (p<0.001). The BP was lower in SHRT than in SHRS (p<0.001). The SHRT and WKYT rats showed higher baroreflex-mediated tachycardia values when compared to their respective sedentary counterparts (p<0.001). Baroreflex bradycardic response in SHRT was higher than in SHRS (p<0.005). The SHRT and WKYT rats showed a decreased sympathetic activity in comparison to their respective sedentary groups (p<0.05). The cardiac vagal tonus was higher in SHRT than in SHRS (p<0.05). Regarding the dynamic transducer properties of peripheral vagus nerve to the heart no difference was observed among the groups. In conclusion, our results demonstrate that exercise training decreased BP in SHR and improved cardiovascular autonomic balance to the heart without changes in transduction properties of peripheral cardiac vagus nerve.

Acute interruption of treatment with nandrolone decanoate is not sufficient to reverse cardiac autonomic dysfunction and ventricular repolarization disturbances in rats

&NA; Anabolic androgenic steroids are a class of synthetic compounds derived from testosterone, eventually used by athletes, to improve physical performance. However, anabolic steroids can also modify normal cardiovascular function. Thus, we investigated cardiac electrophysiological and autonomic abnormalities in rats, through a electrocardiographic variability protocol during and after interruption of administration of nandrolone decanoate (DECA) anabolic steroid. Twenty male Wistar rats (60–70 days old) received DECA (10 mg. kg−1 i.m) once a week or vehicle, during eight weeks. Electrocardiogram was recorded in conscious rats by a noninvasive method, and time and domain analysis of heart rate variability as well as electrocardiogram intervals (QTc / QTd) were performed. Body mass was lower in treated rats compared to control after 4th and 8th weeks, but not at the end of 14th week. QTc and QTd were longer in DECA group compared to control on 4th, 8th, 11th, but equal on 14th week. Cardiac autonomic dysfunction (vagal attenuation) was present on DECA group after 4th week and did not normalize after interruption of treatment. The animals of DECA group showed a correlation between attenuated parasympathetic modulation and increased correct QT interval. Our data allow us to conclude that long‐term treatment with DECA impairs autonomic cardiac physiology, predisposing to cardiovascular risk and sudden death, and interruption of administration does not recovery the normality immediately.

Wearing Colored Glasses can Influence Exercise Performance and Testosterone concentration

Perception of red color is associated with higher testosterone concentration and better human performance. Thus, we evaluated the acute effects of wearing colored-lens glasses on the YoYo intermittent endurance exercise test 2 (YoYoIE2) performance indicators and testosterone concentration. Ten soccer players performed three YoYoIE2 (counterbalanced crossover) wearing colorless (control), blue- or red-lensed glasses (2–4 days of rest in between). YoYoIE2 performance did not differ among the trials ( p >0.05), but blood testosterone increased post-exercise in red compared to red baseline (red=14%, effect size=0.75). Analysis showed faster heart rate recovery ( p <0.05) at 1 min post-test for blue compared to red lenses. Rating of perceived exertion and blood lactate concentration did not differ ( p >0.05) among the trials. Wearing red-colored lenses during high-intensity intermittent exercise increased testosterone concentration, but do not influence performance.

Remodeling of elastic layer of aortic artery after training by swimming in spontaneously hypertensive rats

Hypertension is a major risk factor for cardiovascular diseases, in which the elastic properties of arteries are subjected to high pressure levels, and networks of elastic fibers may develop cleft longitudinal, transverse, breaks and fragmentation, and such structural changes (fibrosis and degradation of elastin) may lead to a decrease in the elasticity of the artery. The descending thoracic aortas of normotensive Wistar Kyoto (WKY) and spontaneously hypertensive rats (SHRs) subjected to physical training through swimming or those of sedentary rats were prepared with hematoxylin-eosin and Verhoff to assess the artery medial. The images were captured with a videocamera coupled to an ordinary light microscope and the images were analyzed with the same program. SHRs showed a larger area of the medial layer of the thoracic aorta (F = 25,764, P, 0.001), and it was observed that rats submitted to physical training through swimming showed a larger area of the thoracic aorta (t = 3.206, P = 0.011). There was a higher percentage of elastic trained (F = 6.536, P = 0.019). To conclude, this study aimed to determine the elastic component of the aortic artery in animals that underwent exercise when compared with those that did not perform the activity, and analyze the relationship between the area of the aortic wall in trained and sedentary animals. The principal conclusion is that the rigidity of the aorta is not increased in SHRs subjected to physical training compared with that of trained WKY animals; however, when sedentary SHRs were analyzed there was a decrease in the elasticcomponent, which can characterize the aortic arterial stiffness in SHRs.

Exercise Training Attenuates Sympathetic Activity and Improves Morphometry of Splenic Arterioles in Spontaneously Hipertensive Rats

Background Alterations in the structure of resistance vessels contribute to elevated systemic vascular resistance in hypertension and are linked to sympathetic hyperactivity and related lesions in target organs. Objective To assess the effects of exercise training on hemodynamic and autonomic parameters, as well as splenic arteriolar damages in male Wistar Kyoto (WKY) and Spontaneously Hypertensive Rats (SHR). Methods Normotensive sedentary (WKYS) and trained (WKYT) rats, and hypertensive sedentary (SHRS) and trained (SHRT) rats were included in this study. After 9 weeks of experimental protocol (swimming training or sedentary control), arterial pressure (AP) and heart rate (HR) were recorded in freely moving rats. We assessed the autonomic control of the heart by sympathetic and vagal autonomic blockade. Morphometric analyses of arterioles were performed in spleen tissues. The statistical significance level was set at p < 0.05. Results Resting bradycardia was observed in both trained groups (WKYT: 328.0 ± 7.3 bpm; SHRT: 337.0 ± 5.2 bpm) compared with their respective sedentary groups (WKYS: 353.2 ± 8.5 bpm; SHRS: 412.1 ± 10.4 bpm; p < 0.001). Exercise training attenuated mean AP only in SHRT (125.9 ± 6.2 mmHg) vs. SHRS (182.5 ± 4.2 mmHg, p < 0.001). The WKYT showed a higher vagal effect (∆HR: 79.0 ± 2.3 bpm) compared with WKYS (∆HR: 67.4 ± 1.7 bpm; p < 0.05). Chronic exercise decreased sympathetic effects on SHRT (∆HR: -62.8 ± 2.8 bpm) in comparison with SHRS (∆HR: -99.8 ± 9.2 bpm; p = 0.005). The wall thickness of splenic arterioles in SHR was reduced by training (332.1 ± 16.0 µm2 in SHRT vs. 502.7 ± 36.3 µm2 in SHRS; p < 0.05). Conclusions Exercise training attenuates sympathetic activity and AP in SHR, which may be contributing to the morphological improvement of the splenic arterioles.