1
|
Kang LS, Masilamani S, Boegehold MA. Juvenile growth reduces the influence of epithelial sodium channels on myogenic tone in skeletal muscle arterioles. Clin Exp Pharmacol Physiol 2017; 43:1199-1207. [PMID: 27560463 DOI: 10.1111/1440-1681.12664] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2015] [Revised: 06/21/2016] [Accepted: 07/14/2016] [Indexed: 02/05/2023]
Abstract
Previous studies have documented that rapid juvenile growth is accompanied by functional changes in the arteriolar endothelium, but much less is known about functional changes in arteriolar smooth muscle over this period. In this study, we investigate the possible contribution of epithelial sodium channels (ENaC) to the myogenic behaviour of arterioles at two stages of juvenile growth. The effects of the ENaC inhibitor benzamil on different levels of myogenic tone were studied in isolated gracilis muscle arterioles from rats aged 21-28 days ("weanlings") and 42-49 days ("juveniles"). ENaC subunit expression in the arteriolar wall was also determined, and the interaction between ENaC and nitric oxide (NO) in regulating vascular tone was explored by combined use of benzamil and NG -monomethyl-l-arginine (l-NMMA). At physiological pressures, both steady-state myogenic tone and the dynamic adjustments in this tone triggered by acute pressure changes were less in juvenile arterioles than in weanling arterioles. α, β and γ ENaC protein was present in arterioles at both ages, but benzamil only had an effect on myogenic tone in weanling arterioles. In these vessels, benzamil increased, rather than decreased, myogenic tone, and this effect was prevented by l-NMMA or endothelial removal. These findings suggest that although ENaC is present in gracilis muscle arterioles of both weanling and juvenile rats, it is not obligatory for the genesis of myogenic activity in these vessels at either age. However, ENaC activity can significantly modulate the level of myogenic tone through stimulation of endothelial NO release at an early stage of growth.
Collapse
Affiliation(s)
- Lori S Kang
- Department of Physiology and Pharmacology, West Virginia University School of Medicine, Morgantown, WV, USA
| | - Shyama Masilamani
- Department of Internal Medicine/Division of Nephrology, Virginia Commonwealth University Medical Center, Richmond, VA, USA
| | - Matthew A Boegehold
- Department of Physiology and Pharmacology, West Virginia University School of Medicine, Morgantown, WV, USA
| |
Collapse
|
2
|
|
3
|
Schlager O, Giurgea A, Hammer A, Charwat-Resl S, Margeta C, Mueller M, Ehringer T, Zehetmayer S, Willfort-Ehringer A, Koppensteiner R, Gschwandtner ME. Impact of age and gender on microvascular function. Eur J Clin Invest 2014; 44:766-74. [PMID: 24942279 DOI: 10.1111/eci.12293] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/24/2014] [Accepted: 06/13/2014] [Indexed: 01/06/2023]
Abstract
BACKGROUND Microcirculatory function can be assessed by postocclusive reactive hyperaemia (PORH) using laser Doppler fluxmetry. Previous studies have shown that PORH reveals microvascular damage at an early stage. In particular, at younger ages, PORH might depend on age and gender. To implement PORH into a larger scale of clinical studies, one has to be aware of the influence of age and gender on microcirculation. The aim of this study was to assess the impact of age and gender on microcirculatory function during adolescence. MATERIALS AND METHODS Within the scope of an epidemiological project, 896 children and adolescents underwent assessment of PORH by laser Doppler fluxmetry. Microcirculatory parameters during PORH (baseline perfusion, biological zero, peak perfusion, time to peak perfusion and recovery time) were analysed in relation to age (by tertiles) and gender. RESULTS Baseline perfusion, biological zero and peak perfusion were lower in children/adolescents in the upper age tertile (12·3-18·1 years) than in the middle (9·8-12·2 years) and lower (4·3-9·7 years) age tertiles (P < 0·0001). In the total of participants, baseline perfusion, biological zero and peak perfusion were higher in males than in females (P < 0·0001). Analysing microcirculatory parameters as a function of age and gender, the sex differences were only apparent in the upper and the middle age tertiles, but not in the lower. CONCLUSIONS During adolescence, PORH is a function of age. At higher age, microvascular reactivity considerably depends on gender, whereas no sex differences are present at younger ages.
Collapse
Affiliation(s)
- Oliver Schlager
- Division of Angiology, Department of Medicine II, Medical University of Vienna, Vienna, Austria
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
4
|
Golub AS, Pittman RN. Bang-bang model for regulation of local blood flow. Microcirculation 2014; 20:455-83. [PMID: 23441827 DOI: 10.1111/micc.12051] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2013] [Accepted: 02/19/2013] [Indexed: 11/27/2022]
Abstract
The classical model of metabolic regulation of blood flow in muscle tissue implies the maintenance of basal tone in arterioles of resting muscle and their dilation in response to exercise and/or tissue hypoxia via the evoked production of vasodilator metabolites by myocytes. A century-long effort to identify specific metabolites responsible for explaining active and reactive hyperemia has not been successful. Furthermore, the metabolic theory is not compatible with new knowledge on the role of physiological radicals (e.g., nitric oxide, NO, and superoxide anion, O2 (-) ) in the regulation of microvascular tone. We propose a model of regulation in which muscle contraction and active hyperemia are considered the physiologically normal state. We employ the "bang-bang" or "on/off" regulatory model which makes use of a threshold and hysteresis; a float valve to control the water level in a tank is a common example of this type of regulation. Active bang-bang regulation comes into effect when the supply of oxygen and glucose exceeds the demand, leading to activation of membrane NADPH oxidase, release of O2 (-) into the interstitial space and subsequent neutralization of the interstitial NO. Switching arterioles on/off when local blood flow crosses the threshold is realized by a local cell circuit with the properties of a bang-bang controller, determined by its threshold, hysteresis, and dead-band. This model provides a clear and unambiguous interpretation of the mechanism to balance tissue demand with a sufficient supply of nutrients and oxygen.
Collapse
Affiliation(s)
- Aleksander S Golub
- Department of Physiology and Biophysics, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, VA, USA.
| | | |
Collapse
|
5
|
Stapleton PA, Minarchick VC, McCawley M, Knuckles TL, Nurkiewicz TR. Xenobiotic particle exposure and microvascular endpoints: a call to arms. Microcirculation 2012; 19:126-42. [PMID: 21951337 DOI: 10.1111/j.1549-8719.2011.00137.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Xenobiotic particles can be considered in two genres: air pollution particulate matter and engineered nanoparticles. Particle exposures can occur in the greater environment, the workplace, and our homes. The majority of research in this field has, justifiably, focused on pulmonary reactions and outcomes. More recent investigations indicate that cardiovascular effects are capable of correlating with established mortality and morbidity epidemiological data following particle exposures. While the preliminary and general cardiovascular toxicology has been defined, the mechanisms behind these effects, specifically within the microcirculation, are largely unexplored. Therefore, the purpose of this review is several fold: first, a historical background on toxicological aspects of particle research is presented. Second, essential definitions, terminology, and techniques that may be unfamiliar to the microvascular scientist will be discussed. Third, the most current concepts and hypotheses driving cardiovascular research in this field will be reviewed. Lastly, potential future directions for the microvascular scientist will be suggested. Collectively speaking, microvascular research in the particle exposure field represents far more than a "niche." The immediate demand for basic, translational, and clinical studies is high and diverse. Microvascular scientists at all career stages are strongly encouraged to expand their research interests to include investigations associated with particle exposures.
Collapse
|
6
|
Butcher JT, Goodwill AG, Frisbee JC. The ex vivo isolated skeletal microvessel preparation for investigation of vascular reactivity. J Vis Exp 2012:3674. [PMID: 22565845 DOI: 10.3791/3674] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
The isolated microvessel preparation is an ex vivo preparation that allows for examination of the different contributions of factors that control vessel diameter, and thus, perfusion resistance(1-5). This is a classic experimental preparation that was, in large measure, initially described by Uchida et al.(15) several decades ago. This initial description provided the basis for the techniques that was extensively modified and enhanced, primarily in the laboratory of Dr. Brian Duling at the University of Virginia(6-8), and we present a current approach in the following pages. This preparation will specifically refer to the gracilis arteriole in a rat as the microvessel of choice, but the basic preparation can readily be applied to vessels isolated from nearly any other tissue or organ across species(9-13). Mechanical (i.e., dimensional) changes in the isolated microvessels can easily be evaluated in response to a broad array of physiological (e.g., hypoxia, intravascular pressure, or shear) or pharmacological challenges, and can provide insight into mechanistic elements comprising integrated responses in an intact, although ex vivo, tissue. The significance of this method is that it allows for facile manipulation of the influences on the integrated regulation of microvessel diameter, while also allowing for the control of many of the contributions from other sources, including intravascular pressure (myogenic), autonomic innervation, hemodynamic (e.g., shear stress), endothelial dependent or independent stimuli, hormonal, and parenchymal influences, to provide a partial list. Under appropriate experimental conditions and with appropriate goals, this can serve as an advantage over in vivo or in situ tissue/organ preparations, which do not readily allow for the facile control of broader systemic variables. The major limitation of this preparation is essentially the consequence of its strengths. By definition, the behavior of these vessels is being studied under conditions where many of the most significant contributors to the regulation of vascular resistance have been removed, including neural, humoral, metabolic, etc. As such, the investigator is cautioned to avoid over-interpretation and extrapolation of the data that are collected utilizing this preparation. The other significant area of concern with regard to this preparation is that it can be very easy to damage cellular components such as the endothelial lining or the vascular smooth muscle, such that variable source of error can be introduced. It is strongly recommended that the individual investigator utilize appropriate measurements to ensure the quality of the preparation, both at the initiation of the experiment and periodically throughout the course of a protocol.
Collapse
Affiliation(s)
- Joshua T Butcher
- Department of Physiology and Pharmacology, Center for Cardiovascular and Respiratory Sciences, West Virginia University, USA
| | | | | |
Collapse
|
7
|
Kang LS, Nurkiewicz TR, Wu G, Boegehold MA. Changes in eNOS phosphorylation contribute to increased arteriolar NO release during juvenile growth. Am J Physiol Heart Circ Physiol 2012; 302:H560-6. [PMID: 22140037 PMCID: PMC3353788 DOI: 10.1152/ajpheart.00277.2011] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/21/2011] [Accepted: 11/14/2011] [Indexed: 02/07/2023]
Abstract
Nitric oxide (NO) mediates a major portion of arteriolar endothelium-dependent dilation in adults, but indirect evidence has suggested that NO contributes minimally to these responses in the young. Isolated segments of arterioles were studied in vitro to verify this age-related increase in NO release and investigate the mechanism by which it occurs. Directly measured NO release induced by ACh or the Ca(2+) ionophore A-23187 was five- to sixfold higher in gracilis muscle arterioles from 42- to 46-day-old (juvenile) rats than in those from 25- to 28-day-old (weanling) rats. There were no differences between groups in arteriolar endothelial NO synthase (eNOS) expression or tetrahydrobiopterin levels, and arteriolar l-arginine levels were lower in juvenile vessels than in weanling vessels (104 ± 6 vs.126 ± 3 pmol/mg). In contrast, agonist-induced eNOS Thr(495) dephosphorylation and eNOS Ser(1177) phosphorylation (events required for maximal activity) were up to 30% and 65% greater, respectively, in juvenile vessels. Juvenile vessels did not show increased expression of enzymes that mediate these events [protein phosphatases 1 and 2A and PKA and PKB (Akt)] or heat shock protein 90, which facilitates Ser(1177) phosphorylation. However, agonist-induced colocalization of heat shock protein 90 with eNOS was 34-66% greater in juvenile vessels than in weanling vessels, and abolition of this difference with geldanamycin also abolished the difference in Ser(1177) phosphorylation between groups. These findings suggest that growth-related increases in arteriolar NO bioavailability may be due at least partially to changes in the regulation of eNOS phosphorylation and increased signaling activity, with no change in the abundance of eNOS signaling proteins.
Collapse
Affiliation(s)
- Lori S Kang
- Center for Cardiovascular and Respiratory Sciences, West Virginia Univ. School of Medicine, 1 Medical Center Dr., PO Box 9105, Morgantown, WV 26506-9105, USA
| | | | | | | |
Collapse
|
8
|
|
9
|
Vascular endothelium-specific overexpression of human catalase in cloned pigs. Transgenic Res 2010; 20:989-1001. [PMID: 21170678 DOI: 10.1007/s11248-010-9473-7] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2010] [Accepted: 12/02/2010] [Indexed: 01/15/2023]
Abstract
The objective of this study was to develop transgenic Yucatan minipigs that overexpress human catalase (hCat) in an endothelial-specific manner. Catalase metabolizes hydrogen peroxide (H(2)O(2)), an important regulator of vascular tone that contributes to diseases such as atherosclerosis and preeclampsia. A large animal model to study reduced endothelium-derived H(2)O(2) would therefore generate valuable translational data on vascular regulation in health and disease. Yucatan minipig fetal fibroblasts stably co-transfected with human catalase (Tie2-hCat) and eGFP expression constructs were isolated into single-cell populations. The presence of the Tie2-hCat transgene in individual colonies of fibroblasts was determined by PCR. Transgenic fibroblasts were used for nuclear transfer into enucleated oocytes by electrofusion. A minimum of 140 cloned embryos were transferred per surrogate sow (n = 4). All four surrogates maintained pregnancies and piglets were delivered by cesarean section. Nine male piglets from three of the four litters carried the Tie2-hCat transgene. Expression of human catalase mRNA and overall elevated catalase protein in isolated umbilical endothelial cells from transgenic piglets were verified by RT-PCR and western blot, respectively, and endothelial localization was confirmed by immunohistochemistry. Increased enzymatic activity of catalase in transgenic versus wild-type endothelial cells was inferred based on significantly reduced levels of H(2)O(2) in culture. The similarities in swine and human cardiovascular anatomy and physiology will make this pig model a valuable source of information on the putative role of endothelium-derived H(2)O(2) in vasodilation and in the mechanisms underlying vascular health and disease.
Collapse
|
10
|
Abstract
Endothelial dysfunction can develop at an early age in children with risk factors for cardiovascular disease. A clear understanding of the nature of this dysfunction and how it can worsen over time requires detailed information on the normal growth-related changes in endothelial function on which the pathological changes are superimposed. This review summarizes our current understanding of these normal changes, as derived from studies in four different mammalian species. Although the endothelium plays an important role in controlling vascular tone from birth onward, the vasoactive molecules that mediate this control often change during postnatal or juvenile growth. The specifics of this transition to an adult endothelial cell phenotype can vary depending on the vascular bed. During growth, the contribution of nitric oxide to endothelium-dependent dilation generally increases in the lung, cerebral cortex, and skeletal muscle, but decreases in the intestine. Endothelial capacity for release of other vasoactive factors (e.g., cyclooxygenase products, hydrogen peroxide, carbon monoxide) can also increase or decrease during growth. Although these changes have been well documented, there is less information on their underlying cellular or molecular events. Further research is required to clarify these mechanisms, and to evaluate the functional significance of such shifts in endothelial phenotype.
Collapse
MESH Headings
- Animals
- Animals, Newborn
- Cardiovascular Diseases/etiology
- Cardiovascular Diseases/physiopathology
- Cerebrovascular Circulation/physiology
- Endothelium, Vascular/growth & development
- Endothelium, Vascular/physiology
- Enterocolitis, Necrotizing/etiology
- Enterocolitis, Necrotizing/physiopathology
- Humans
- Infant, Newborn
- Intestines/blood supply
- Models, Animal
- Muscle, Skeletal/blood supply
- Muscle, Smooth, Vascular/growth & development
- Muscle, Smooth, Vascular/physiology
- Nitric Oxide/physiology
- Persistent Fetal Circulation Syndrome/etiology
- Persistent Fetal Circulation Syndrome/physiopathology
- Pulmonary Circulation/physiology
- Rats
- Risk Factors
- Sheep
- Swine
- Vascular Resistance/physiology
Collapse
Affiliation(s)
- Matthew A Boegehold
- Department of Physiology and Pharmacology and Center for Cardiovascular and Respiratory Sciences, Robert C. Byrd Health Sciences Center, West Virginia University School of Medicine, Morgantown, WV 26505-9105, USA.
| |
Collapse
|
11
|
Samora JB, Goodwill AG, Frisbee JC, Boegehold MA. Growth-dependent changes in the contribution of carbon monoxide to arteriolar function. J Vasc Res 2009; 47:23-34. [PMID: 19672105 DOI: 10.1159/000231718] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2008] [Accepted: 12/31/2008] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND/AIMS Endothelium-dependent dilation of skeletal muscle arterioles is mediated by unknown factors in very young rats. We assessed the possible contribution of carbon monoxide (CO) to this dilation and to dilation in older animals. METHODS The effects of de-endothelialization or various pharmacological inhibitors on responses to CO or endothelium-dependent dilators were studied in gracilis muscle arterioles from rats at 3-4 weeks ('weanlings') and 6-7 weeks ('juveniles'). RESULTS Exogenous CO constricted, rather than dilated, arterioles from both age groups. This constriction was reduced by endothelial removal or NOS inhibition in juvenile, but not weanling, arterioles. In contrast, this constriction was abolished by K(+) channel inhibition in weanling, but not juvenile, arterioles. The heme precursor delta-aminolevulinic acid constricted juvenile arterioles but did not affect weanling arterioles. The heme oxygenase inhibitor chromium (III) mesoporphyrin IX abolished the endothelium-dependent dilation of juvenile arterioles to simvastatin, and reduced ACh- and simvastatin-induced dilations of weanling arterioles. CONCLUSION These findings suggest that relatively high concentrations of exogenous CO can cause constriction by inhibiting endothelium-derived NO in juvenile arterioles and inhibiting K(+) channels in weanling arterioles. Endogenous CO produced at lower concentrations can contribute to endothelium-dependent dilation in both age groups.
Collapse
Affiliation(s)
- Julie Balch Samora
- Department of Physiology and Pharmacology, and Center for Interdisciplinary Research in Cardiovascular Sciences, West Virginia University School of Medicine, Morgantown, W. Va., USA
| | | | | | | |
Collapse
|
12
|
Kang LS, Reyes RA, Muller-Delp JM. Aging impairs flow-induced dilation in coronary arterioles: role of NO and H(2)O(2). Am J Physiol Heart Circ Physiol 2009; 297:H1087-95. [PMID: 19617414 DOI: 10.1152/ajpheart.00356.2009] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Aging contributes significantly to the development of cardiovascular disease and is associated with elevated production of reactive oxygen species (ROS). The beneficial effects of nitric oxide (NO)-mediated vasodilation are quickly abolished in the presence of ROS, and this effect may be augmented with aging. We previously demonstrated an age-induced impairment of flow-induced dilation in rat coronary arterioles. Therefore, the purpose of this study was to determine the effects of O(2)(-) scavenging, as well as removal of H(2)O(2), the byproduct of O(2)(-) scavenging, on flow-mediated dilation in coronary resistance arterioles of young (4 mo) and old (24 mo) male Fischer 344 rats. Flow increased NO and H(2)O(2) production as evidenced by enhanced diaminofluorescein and dichlorodihydrofluorescein fluorescence, respectively, whereas aging reduced flow-induced NO and H(2)O(2) production. Endothelium-dependent vasodilation was evaluated by increasing intraluminal flow (5-60 nl/s) before and after treatment with the superoxide dismutase mimetic Tempol (100 muM), the H(2)O(2) scavenger catalase (100 U/ml), or Tempol plus catalase. Catalase reduced flow-induced dilation in both groups, whereas Tempol and Tempol plus catalase diminished vasodilation in young but not old rats. Tempol plus deferoxamine (100 muM), an inhibitor of hydroxyl radical formation, reversed Tempol-mediated impairment of flow-induced vasodilation in young rats and improved flow-induced vasodilation in old rats compared with control. Immunoblot analysis revealed increases in endogenous superoxide dismutase, catalase, and nitrotyrosine protein levels with aging. Collectively, these data indicate that NO- and H(2)O(2)-mediated flow-induced signaling decline with age in coronary arterioles and that elevated hydroxyl radical formation contributes to the age-related impairment of flow-induced vasodilation.
Collapse
Affiliation(s)
- Lori S Kang
- Department of Physiology and Pharmacology, West Virginia University School of Medicine, Morgantown, West Virginia, USA
| | | | | |
Collapse
|
13
|
Copp SW, Ferreira LF, Herspring KF, Hirai DM, Snyder BS, Poole DC, Musch TI. The effects of antioxidants on microvascular oxygenation and blood flow in skeletal muscle of young rats. Exp Physiol 2009; 94:961-71. [PMID: 19502293 DOI: 10.1113/expphysiol.2009.048223] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Alterations of skeletal muscle redox state via antioxidant supplementation have the potential to impact contractile function and vascular smooth muscle tone. The effects of antioxidants on the regulation of muscle O(2) delivery-O(2) utilization (Q(O(2)m/V(O(2)m)) matching (which sets the microvascular partial pressure of O(2); P(O(2)mv)) in young healthy muscle are not known. Therefore, the purpose of this study was to test the effects of acute antioxidant supplementation on rat spinotrapezius muscle force production, blood flow, V(O(2)m) and P(O(2)mv) (phosphorescence quenching). Anaesthetized male Fischer 344 x Brown Norway rats (6-8 months old) had their right spinotrapezius muscles either exposed for measurement of blood flow and (n = 13) or exteriorized for measurement of muscle force production (n = 6). Electrically stimulated 1 Hz twitch contractions (approximately 7-9 V) were elicited for 180 s, and measurements were made before and after acute intra-arterial antioxidant supplementation (76 mg kg(-1) ascorbic acid, 52 mg kg(-1) tempol) dissolved in saline and infused over 30 min. The principal effects of antioxidants were a approximately 25% decrease (P < 0.05) in contracting spinotrapezius muscle force production concurrent with reductions in muscle blood flow and V(O(2)m) at rest and during contractions (P < 0.05 for both). Antioxidant supplementation reduced the resting baseline P(O(2)mv) (before, 29.9 +/- 1.2 mmHg; after, 25.6 +/- 1.3 mmHg; P < 0.05), and this magnitude of depression was sustained throughout the rest-to-exercise transition (steady-state value before, 16.4 +/- 0.7 mmHg; after, 13.6 +/- 0.9 mmHg; P < 0.05). In addition, the time constant of the P(O(2)mv) decrease was reduced after antioxidant supplementation (before, 23.4 +/- 4.3 s; after, 15.6 +/- 2.7 s; P < 0.05). These results demonstrate that antioxidant supplementation significantly impacts the control of (Q(O(2)m/V(O(2)m)) in young rats at rest and during contractions.
Collapse
Affiliation(s)
- Steven W Copp
- Department of Kinesiology, Kansas State University, Manhattan, KS 66506-5802, USA
| | | | | | | | | | | | | |
Collapse
|
14
|
Samora JB, Frisbee JC, Boegehold MA. Increased myogenic responsiveness of skeletal muscle arterioles with juvenile growth. Am J Physiol Heart Circ Physiol 2008; 294:H2344-51. [PMID: 18375725 DOI: 10.1152/ajpheart.00053.2008] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Previous studies from this laboratory suggest that during juvenile growth, structural changes in the arteriolar network are accompanied by changes in some of the mechanisms responsible for regulation of tissue blood flow. To test the hypothesis that arteriolar myogenic behavior is altered with growth, we studied gracilis muscle arterioles isolated from Sprague-Dawley rats at two ages: 21-28 and 42-49 days. When studied at their respective in vivo pressures, the myogenic index (instantaneous slope of the active pressure-diameter curve) of arterioles from 42-49-day-old rats was more negative than that of arterioles from 21-28-day-old rats, indicating greater myogenic responsiveness. Endothelial denudation, or prostaglandin H(2) (PGH(2))/thromboxane A(2) (TxA(2)) receptor antagonism without denudation, significantly reduced the myogenic responsiveness of arterioles from the older rats over a wide range of pressures but had no consistent effects on the myogenic responsiveness of arterioles from the younger rats. The heme oxygenase inhibitor chromium (III) mesoporphyrin IX chloride had no effect on the myogenic activity of arterioles from either age group. These findings indicate that microvascular growth in young animals is accompanied by an increase in the myogenic behavior of arterioles, possibly because PGH(2) or TxA(2) assumes a role in reinforcing myogenic activity over this period. As a result, the relative contribution of myogenic activity to blood flow regulation in skeletal muscle may increase during rapid juvenile growth.
Collapse
Affiliation(s)
- Julie Balch Samora
- Center for Interdisciplinary Research in Cardiovascular Sciences, Robert C. Byrd Health Sciences Center, West Virginia University School of Medicine, Morgantown, WV 26505-9105, USA
| | | | | |
Collapse
|