Berkowitz DE, Brooks-Asplund E, Mo Z, Winters B, Nyhan D, Shoukas A.

Circulation. 1999 Nov 2; 100: I-134.

Johns Hopkins Univ, Baltimore, MD, USA.

INTRODUCTION: Orthostatic intolerance is a significant problem for astronauts returning from microgravity. Mechanisms of orthostasis remain incompletely understood. We hypothesized that impaired vasoreactivity is an important factor in orthostatic hypotension. We have recently demonstrated impaired vasoreactivity in aortic rings from a rat hind limb unweighted model (HLU) of microgravity. We now demonstrate impaired vasoreactivity in mesenteric microvessels (MM) as well as reversibility of the phenomenon with return to normal posture (1 g). METHODS: Rats were HLU for 3 weeks, then sacrificed. MM were dissected, cannulated at both end with micropipettes, placed in microvascular chambers, internal diameter measured, using video-microscopy, and dose response curves generated to KCl, phenylephrine and U46619. A separate group of animals were HLU, the right femoral artery (FA) excised and animals recovered. Following 3 weeks of normal posture (HLU+3) animals were sacrificed and the contralateral FA excised and placed in organ chambers for isometric tension measurements to above agonists. RESULTS: There is a significant impairment in vasoreactivity to PE as manifest by a shift in the dose response curve to the right in MMV vs control (log EC50 -5.5 +/- 0.2 vs. -6.0 +/- 0.2, p<0.05, n=4). 3 weeks of normal posture (HLU + 3) reversed the impaired alpha-1 AR mediated vasoreactivity in HLU (log EC50 -5.6 -/+ 0.l vs. 5.1 +/- 0.l, p<0.05, n=6). CONCLUSIONS: Impaired vasoreactivity in resistance MMV to alpha-1AR agonists may be an important mechanism of orthostatic intolerance following cardiovascular deconditioning. This process appears to reverse with exposure to grave. [graph: see text]

Publication Types:

• Meeting Abstracts

Keywords:

• 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid
• Animals
• Arteries
• Cardiovascular Deconditioning
• Femoral Artery
• Hindlimb
• Hindlimb Suspension
• Hypotension, Orthostatic
• Mesentery
• Models, Biological
• Muridae
• Phenylephrine
• Rats
• Rats, Sprague-Dawley
• Weightlessness
• Weightlessness Simulation
• NASA Discipline Cardiopulmonary
• Non-NASA Center

Other ID:

• 20603509

UI: 102194946

From Meeting Abstracts