Rat small mesenteric artery function after hindlimb suspension.
To determine whether simulated microgravity in rats is associated with vascular dysfunction, we measured responses of isolated, pressurized mesenteric resistance artery segments (157- to 388-microm ID) to vasoconstrictors, pressure, and shear stress after 28-day hindlimb suspension (HS). Results indicated no differences between HS and control (C) groups in 1) sensitivity or maximal responses to vasoconstrictors (norepinephrine, phenylephrine, serotonin, KCl); 2) ID, external diameter, or ratio of wall thickness to ID; 3) distensibility; or 4) vasodilatory responses to shear stress. Myogenic tone was attenuated (P < 0.05) in HS arteries vs. C, as evidenced by 1) decreased magnitude of tone in larger vessels (second-order branch off superior mesenteric artery, 261- to 388-microm ID) at pressures >/=40 mmHg in the presence of phenylephrine (10(-7) M) and 2) decreased magnitude of tone in smaller vessels (third-order branch off superior mesenteric artery, 157- to 277-microm ID), which exhibited spontaneous tone, at pressures > or =70 mmHg. This attenuation of myogenic tone after HS could contribute to orthostatic intolerance because myogenic tone contributes to the overall tone of resistance arteries.
Looft-Wilson
R C
RC
Department of Physiology and Biophysics, University of Iowa, Iowa City, Iowa 52242, USA.
Gisolfi
C V
CV
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D001794:Blood Pressure; D019417:Hindlimb Suspension / Q000502:physiology*; D066298:In Vitro Techniques; D008297:Male; D008638:Mesenteric Arteries / Q000187:drug effects / Q000502:physiology*; D018482:Muscle, Skeletal / Q000098:blood supply / Q000187:drug effects / Q000502:physiology*; D009638:Norepinephrine / Q000494:pharmacology; D011189:Potassium Chloride / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012701:Serotonin / Q000494:pharmacology; D014655:Vascular Resistance / Q000187:drug effects; D014661:Vasoconstriction / Q000187:drug effects / Q000502:physiology
D012701:Serotonin; D011189:Potassium Chloride; D000109:Acetylcholine; D009638:Norepinephrine