Effects of antioxidants on contracting spinotrapezius muscle microvascular oxygenation and blood flow in aged rats

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dc.contributor.author Herspring, Kyle F.
dc.date.accessioned 2008-05-06T19:26:19Z
dc.date.available 2008-05-06T19:26:19Z
dc.date.issued 2008-05-06T19:26:19Z
dc.identifier.uri http://hdl.handle.net/2097/700
dc.description.abstract Aged rats exhibit a decreased muscle microvascular O[subscript]2 partial pressure (PO[subcript]2mv) at rest as well as during contractions compared to young rats and this may contribute to their reduced exercise tolerance. Age-related reductions in nitric oxide (NO) bioavailability due, in part, to elevated reactive O[subscript]2 species (ROS) constrain muscle blood flow (Qm). Therefore, antioxidants may restore NO bioavailability, Qm and ameliorate the reduction in PO[subscript]2mv and hence the decrease in exercise tolerance seen in aged rats. PURPOSE: To test the hypothesis that antioxidants would elevate Qm at rest and during contractions and therefore PO[subscript]2mv in aged muscle. METHODS: PO[subscript]2mv and Qm were measured in the spinotrapezius while muscle oxygen consumption (VO[subscript]2m) was estimated in 20 anesthetized male Fisher 344 x Brown Norway hybrid (F344xBN) rats at rest and during 1 Hz contractions before and after antioxidant intravenous infusion (76mg/kg vitamin C and 52mg/kg tempol). Moreover, muscle force production was measured in a subset of animals. RESULTS: Before infusion, contractions invoked a biphasic PO[subscript]2mv that fell from 30.6 [plus or minus] 0.9 mmHg to a nadir of 16.8 [plus or minus] 1.2 mmHg with an 'undershoot' of 2.8 [plus or minus] 0.7 mmHg below the subsequent steady-state (19.7 [plus or minus] 1.2 mmHg). Antioxidants elevated baseline PO[subscript]2mv to 35.7 [plus or minus] 0.8 mmHg (P<0.05) and reduced or abolished the 'undershoot' (P<0.05) without changing the steady-state contracting PO[plus or minus]2mv. Antioxidants did not change Qm at rest but during contractions Qm was reduced from 157 [plus or minus] 28 to 91 [plus or minus] 15 ml min[superscript]-1 100g[superscript]-1 (P<0.05). Antioxidants produced no significant effect on VO[subscript]2m. However, antioxidant supplementation produced a 16.5% decrease (P<0.05) in muscle force production that occurred within the first contraction and remained throughout the duration of stimulation. In addition, the ratio of muscle force production to VO[subscript]2m (F/VO[subscript]2m) actually increased from 0.92 [plus or minus] 0.03 to 1.06 [plus or minus] 0.6 (P<0.05) following infusion of antioxidants. CONCLUSION: Antioxidant supplementation significantly alters the balance between muscle O[subscript]2 delivery and VO[subscript]2 at rest and during contractions, which modifies the microvascular PO[subscript]2mv profile. Specifically, antioxidants elevate PO[subscript]2mv, which improves the potential for diffusive blood-myocyte flux. This effect arises, in part, from the unanticipated fall in muscle force production consequent to antioxidant supplementation. en
dc.language.iso en_US en
dc.publisher Kansas State University en
dc.subject aging en
dc.subject muscle microvascular oxygenation en
dc.subject blood flow en
dc.subject antioxidant supplementation en
dc.title Effects of antioxidants on contracting spinotrapezius muscle microvascular oxygenation and blood flow in aged rats en
dc.type Thesis en
dc.description.degree Master of Science en
dc.description.level Masters en
dc.description.department Department of Kinesiology en
dc.description.advisor Timothy I. Musch en
dc.subject.umi Health Sciences, Health Care Management (0769) en
dc.subject.umi Health Sciences, Medicine and Surgery (0564) en
dc.date.published 2008 en
dc.date.graduationmonth May en

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