Alterations in visceral resistance artery function following simulated microgravity /
During orthostasis, approximately 45% of the elevation in peripheral vascular resistance occurs through constriction of the renal and splanchnic vasculature. Because rodents experience orthostatic hypotension following hindlimb unloading (HU), a model to simulate microgravity, the purpose of this s...
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| Format: | Thesis Book |
| Language: | English |
| Published: |
[Place of publication not identified] :
[publisher not identified] ;
2002.
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| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=764785871&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | During orthostasis, approximately 45% of the elevation in peripheral vascular resistance occurs through constriction of the renal and splanchnic vasculature. Because rodents experience orthostatic hypotension following hindlimb unloading (HU), a model to simulate microgravity, the purpose of this study was to determine if 14 or 28 days of HU alters vasoconstrictor responsiveness of mesenteric, renal and splenic resistance vessels. Mesenteric, renal, and splenic resistance arteries from control and HU rats were dissected free, cannulated on glass micropipettes, pressurized, and studied in vitro. Mesenteric and splenic arteries were exposed to step changes in intralumenal pressure ranging from 30 to 180 cmH₂O to determine myogenic responsiveness. Vasoconstrictor properties of mesenteric resistance arteries were characterized by establishing concentration-response curves for potassium chloride, norepinephrine, and caffeine. Renal and splenic arteries were exposed to potassium chloride, norepinephrine, and arginine vasopressin to determine vasoconstrictor responsiveness. In addition, renal and splenic arteries were tested for vasodilatory responsiveness to acetylcholine and sodium nitroprusside. Myogenic properties were unaltered by HU in both splenic and mesenteric arteries. Vasoconstrictor and vasodilator responsiveness of splenic resistance arteries were also unaltered by HU. However, significant increases in renal vasoconstrictor responsiveness to potassium chloride and vasodilator responsiveness to acetylcholine were found following HU. Mesenteric vasoconstrictor responsiveness to potassium chloride, norepinephrine, and caffeine was significantly diminished by HU. These data suggest that HU-induced orthostatic intolerance may be due in part to altered vasoconstrictor properties of mesenteric resistance arteries and vasodilator properties of renal resistance arteries. |
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| Item Description: | Vita. "Major Subject: Kinesiology". |
| Physical Description: | ix, 61 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilm Inc. |
| Bibliography: | Includes bibliographical references (leaves 50-60). |