Exercise training alters endothelium-dependent vasoreactivity of rat abdominal aorta

Abstract

We tested the hypothesis that adaptations in peripheral arterial vasoreactivity are induced by exercise training. Male rats were trained to run on a treadmill at 30 m/min (15 degrees incline) for 1 h/day 5 days/wk for 10-12 wk. Efficacy was indicated by a 51% increase (P < 0.05) in citrate synthase activity in soleus muscle of exercise-trained (ET) rats compared with that of sedentary (SED) control rats. Responses to vasoactive compounds were examined in vitro using rings of abdominal aorta. Maximal isometric contractile tension evoked by KCl, norepinephrine (NE), and phenylephrine were not different between groups; sensitivity to phenylephrine was also not different between groups. However, sensitivity was lower for both KCl and NE in vessels from ET animals. Endothelium removal did not influence KCl sensitivity but did abolish the difference in NE sensitivity of vessel segments between ET and SED animals. Maximal vasodilator responses induced by acetylcholine (ACh; NE or prostaglandin F2 alpha preconstriction) were greater in vessel rings from ET rats. However, dilatory responses by sodium nitroprusside (NE or prostaglandin F2 alpha preconstriction) and forskolin (NE preconstriction) were not different between groups, indicating that the augmented ACh-induced dilatory response resulted from an adaptation of the endothelium. Blockade of nitric oxide synthase activity diminished ACh-induced vasodilation by 79 and 100% in SED and ET rats, respectively. These results indicate that training alters vasomotor function in rat abdominal aortas through adaptations of both endothelium and smooth muscle.

Thyroid status and nitric oxide in rat arterial vessels

“…We (Delp et al 1995, McAllister et al 2000 and others (Vargas et al 1995) have found endothelium-dependent dilation of rat vasculature to be blunted in hypothyroidism; conversely, we (McAllister et al 1998(McAllister et al , 2000 and others (Scivoletto et al 1986, Vargas et al 1995, Honda et al 2000 have observed augmented endothelium-dependent vasodilation in the hyperthyroid state. Since a primary mediator of endothelium-dependent dilation in vasculature of the rat is NO (Delp et al 1993), our findings collectively suggest that alterations in endothelium-dependent vasodilation with changes in thyroid status are, in part, accounted for by an altered capacity for NO formation. It is clear, however, that changes in NO formation do not solely account for altered endothelium-dependent vasodilation.…”

“…Collectively, these findings suggest that thyroid status primarily affects the vascular endothelium. Endotheliumdependent dilation of the rat aorta is primarily mediated by nitric oxide (NO) (Delp et al 1993). We therefore hypothesized that altered endothelium-dependent vasodilation with changes in thyroid status is due to changes in the capacity for NO formation, as reflected by NO synthase (NOS) activity.…”

Exercise training enhances relaxation of the isolated guinea-pig saphenous artery in response to acetylcholine

“…†P < 0.05 CON versus EX. Delp & Laughlin, 1997;Delp et al 1993), but not short-term (1 day to 2 weeks; Delp & Laughlin, 1997), treadmill running in rats increases the maximal responsiveness of abdominal aortic rings to acetylcholine. In a recent study training (10-12 weeks treadmill running) did not alter the dilatation in response to acetylcholine of isolated rat soleus feed arteries (Jasperse & Laughlin, 1999).…”

Atherosclerosis and Physical Activity

“…87,88 Higashi et al had shown that long-term physical exercise improved endothelium-dependent vasorelaxation through an increase in the release of NO in normotensive and hypertensive subjects. 89 Exercise training for only four weeks has been shown to increase basal nitric oxide production in hypercholesterolaemic patients, independent of lipid profile modification.…”