Early increases in coronary vascular reserve in exercised rats are independent of cardiac hypertrophy

Abstract

To evaluate the relationship between the physiological cardiac hypertrophy associated with physical training and the increases in vascular capacitance associated with this stimuli, male and female rats trained by a swimming program were studied. Both sexes were used so that the coronary vascular response to exercise could be studied in the presence (females) and absence (males) of cardiac hypertrophy. Coronary vascular reserve was assessed in isolated retrograde buffer-perfused hearts under conditions of minimal coronary resistance (15 microM adenosine or anoxia). Both groups demonstrated an increase in coronary vascular reserve after 8 wk of exercise swim training, male animals increasing flow (per g of myocardium) by 15% and females by 18%. When the time course of this response was compared in female animals with the time course of the development of myocardial hypertrophy, it was evident that the vascular changes occurred early, greater than 80% of the response was seen within the first 10 days of exercise, compared with an approximately 35% increase in cardiac mass. These data suggest that the vascular response to exercise swim training is independent of the hypertrophic response and further that the increase in coronary vascularity is an early event in the cardiac adaptation to a physiological load.

Voluntary physical exercise and coronary flow velocity reserve: a transthoracic colour Doppler echocardiography study in spontaneously hypertensive rats

“…Indeed, following the primary adenosineinduced peripheral vasodilation, this vascular bed constitutes a rate-limiting site for further flow-mediated vasodilation. By using a Langendorff perfusion system, swim-training studies in WKY rats have revealed an increased CFR after 8 weeks of exercise [33], which further supports our present findings.…”

“…This suggests that exercise-induced cardiac hypertrophy is of an eccentric, rather than concentric, nature, as evident in hypertension, which is associated with decreased CFVR [47]. The lack of association between LVM and CFVR in our present study population suggests further that the improved CFR in response to exercise is independent of exerciseinduced cardiac hypertrophy, an observation supported by Buttrick et al [33].…”

Regulation of Coronary Blood Flow During Exercise

“…A) MAXIMAL CORONARY BLOOD FLOW. There is controversy as to whether maximal coronary blood flow is increased following physical conditioning, with investigators reporting either no change (40,67,77,93,110,364,506,541,619) or an increase (48,86,129,344,351,366,451,535) in blood flow capacity. Several factors may contribute to the differing results, including differences in species, sex, and age of the experimental animals, as well as the type, intensity, and duration of the exercise-training protocol.…”

Coronary Vasodilator Capacity and Epicardial Vessel Remodeling in Physiological and Hypertensive Hypertrophy

“…4,5 Experimental studies suggest an exercise-induced protective adaptation in coronary circulation, which may include both structural changes 6,7 and changes in vasomotor responses. 8 -10 It was demonstrated that in normotensive animals, such as rat, 11,12 dog, 13 and swine, 7 chronic exercise training results in an improvement of coronary vasodilator reserve. By contrast, studies comparing coronary vasodilator capacity in hypertensive patients with LVH and physically trained subjects with similar age and LV mass are not available.…”