| Impaired but reversible vascular reactivity in a rat model of microgravity. |
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Soon Yul Kim, Hyun Kyo Lim, Young Bok Lee, Jae Chan Choi, Jong Taek Park, Myoung Chan Ahn, Kwang Ho Lee |
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Department of Anesthesiology and Pain Medicine, Yonsei University Wonju College of Medicine, Wonju, Korea. khlee6006@yonsei.ac.kr |
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| Abstract |
BACKGROUND
The hindlimb unweighting (HLU) rat model mimics cardiovascular deconditioning following microgravity or human bed rest, particularly for the development of orthostatic intolerance. We have examined vascular responses to alpha1 adrenergic and non-alpha1 adrenergic agonists in vitro. We have also explored the reversibility of the contractile abnormalities observed.
METHODS
Dose-response curves were generated to phenylephrine (PE) and norepinephrine (NE) (10(-9) to 10(-4) M), U46619 (U4) (10(-10) to 10(-6) M) at one-half log order intervals in controls (n = 6), HLU (n = 6), or recovered rats (n = 6). EC(50)s and maximal responses (E(max)) were calculated by nonlinear logistic regression analysis with PRIZM software (Graphpad, Mountain View, CA).
RESULTS
Simulated microgravity results in attenuated contractile responses to both alpha1 adrenergic and non-alpha1 adrenergic agonists, but the impaired contractile phenomenon reverses with time.
CONCLUSIONS
The decreased vascular reactivity after microgravity and prolonged bed rest could cause attenuated baroreflex function and produce orthostatic intolerance, but that problem resolved with time. |
| Key Words:
hindlimb unweighting; microgravity; orthostatic intolerance |
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