Hindlimb unloading in young rats and advanced age both reduced maximal isometric contractile force and impaired vasorelaxation responses in isolated aortic rings compared to young controls.
Does hindlimb unloading and old age alter aortic vasoreactivity in rats?
Both advanced age and physical inactivity (hindlimb unloading) independently impair aortic vasoreactivity in rats, characterized by decreased contractile force and impaired vasorelaxation.
Prolonged bed rest in young adults leads to a number of cardiovascular alterations, including orthostatic intolerance and decreased exercise capacity. Similar changes occur with advanced age. These modifications of cardiovascular function have been suggested to be causally related to changes in peripheral vascular reactivity. Using rat hindlimb unloading as an animal model of physical inactivity, this study was designed to determine whether prolonged decreases in weight-bearing activity induce changes in vascular reactivity that are similar to those occurring in senescent rats and whether the imposition of inactivity on old rats further modifies any age-related alterations in vasomotor responsiveness. Responses to vasoactive compounds were examined in vitro by using isolated abdominal aortic rings. Maximal isometric contractile force evoked by the vasoconstrictors KCl, norepinephrine (NE), and arginine vasopressin was lower in aortic segments from young hindlimb-unloaded (YHU), old control (OC), and old hindlimb-unloaded (OHU) rats compared with that from young control (YC) rats. Sensitivity mean effective concentration (EC50) to KCl was enhanced in segments from both old and unloaded animals compared with YC rats, but EC50 values for the other constrictors were not different among groups. Vasorelaxation responses induced by acetylcholine (10(-7) M NE preconstriction) were lower in vessel rings from OC (1 x 10(-7) to 3 x 10(-6) M), YHU (10(-7) to 10(-5) M), and OHU (10(-7) to 10(-5) M) rats than those from YC animals. In addition, vessel rings from OC, YHU, and OHU rats were less sensitive to sodium nitroprusside-induced relaxation.(ABSTRACT TRUNCATED AT 250 WORDS)
Delp et al. (Thu,) conducted a other in Physical inactivity and aging (animal model). Hindlimb unloading and advanced age vs. Young control rats was evaluated on Maximal isometric contractile force and sensitivity to vasoactive compounds in isolated abdominal aortic rings. Hindlimb unloading in young rats and advanced age both reduced maximal isometric contractile force and impaired vasorelaxation responses in isolated aortic rings compared to young controls.