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Stokes SM, Bertin FR, Stefanovski D, Belknap JK, Medina-Torres CE, Pollitt CC, van Eps AW. Lamellar energy metabolism and perfusion in the euglycaemic hyperinsulinaemic clamp model of equine laminitis. Equine Vet J 2020; 52:577-584. [PMID: 31845378 DOI: 10.1111/evj.13224] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2019] [Revised: 10/29/2019] [Accepted: 12/04/2019] [Indexed: 01/19/2023]
Abstract
BACKGROUND Hyperinsulinaemia is associated with the development of endocrinopathic laminitis; however, the mechanisms remain unclear. OBJECTIVES Evaluate the effects of hyperinsulinaemia on lamellar energy metabolism and perfusion during laminitis development. STUDY DESIGN In vivo experiment. METHODS Eight Standardbred horses were instrumented with a microdialysis probe in the lamellae of a forelimb. A 24 hours baseline period (BASELINE) was followed by 48 hours of a continuous euglycaemic hyperinsulinaemic clamp (EHC) from 24 to 72 hours (CLAMP). Microdialysate was collected every 6 hours and analysed for glucose, lactate and pyruvate concentrations and lactate-to-pyruvate ratio (L:P). Microdialysis urea clearance was used to estimate lamellar tissue perfusion. Archived microdialysis samples from six identically instrumented Standardbred horses served as controls (CON). Variables were compared over time and between EHC and CON horses using a mixed-effects linear regression model. RESULTS Glucose concentration decreased during the CLAMP period in CON and EHC horses (P < .001), but there was no difference between CON and EHC (P > .9). Lactate concentration increased during the CLAMP period in CON and EHC horses (P < .001), however, the rate of increase was significantly higher in EHC horses relative to CON (P = .014). There was a relative increase in pyruvate concentration in EHC horses compared with CON during the CLAMP period (P = .03). L:P increased significantly in CON horses during the CLAMP period (P < .001) but not in EHC (P = .1). Urea clearance did not change in CON (P = .9) or EHC (P = .05) during the CLAMP, but did increase in EHC relative to CON (P = .02). MAIN LIMITATIONS The effects of microdialysis probe implantation on perfusion and metabolism remain unclear. The EHC model may not mimic natural endocrinopathic laminitis. CONCLUSIONS Laminitis developed without evidence of lamellar hypoperfusion or energy stress. Therapies to improve perfusion are unlikely to affect the initial development of endocrinopathic laminitis.
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Affiliation(s)
- Simon M Stokes
- Australian Equine Laminitis Research Unit, School of Veterinary Science, The University of Queensland, Gatton, Qld, Australia
| | - Francois R Bertin
- Australian Equine Laminitis Research Unit, School of Veterinary Science, The University of Queensland, Gatton, Qld, Australia
| | - Darko Stefanovski
- New Bolton Center, Department of Clinical Studies, School of Veterinary Medicine, University of Pennsylvania, Kennett Square, Pennsylvania
| | - James K Belknap
- Department of Veterinary Clinical Sciences, College of Veterinary Medicine, The Ohio State University, Columbus, Ohio
| | - Carlos E Medina-Torres
- Australian Equine Laminitis Research Unit, School of Veterinary Science, The University of Queensland, Gatton, Qld, Australia
| | - Christopher C Pollitt
- Australian Equine Laminitis Research Unit, School of Veterinary Science, The University of Queensland, Gatton, Qld, Australia
| | - Andrew W van Eps
- Australian Equine Laminitis Research Unit, School of Veterinary Science, The University of Queensland, Gatton, Qld, Australia.,New Bolton Center, Department of Clinical Studies, School of Veterinary Medicine, University of Pennsylvania, Kennett Square, Pennsylvania
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Zizzadoro C, Caruso M, Punzi S, Crescenzo G, Zongoli F, Belloli C. A comparative study between responses of isolated bovine and equine digital arteries to vasoactive mediators. J Vet Pharmacol Ther 2017; 41:51-59. [DOI: 10.1111/jvp.12436] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2016] [Accepted: 06/07/2017] [Indexed: 01/17/2023]
Affiliation(s)
- C. Zizzadoro
- Division of Veterinary Pharmacology and Toxicology; Department of Veterinary Medicine; University of Bari; Valenzano Bari Italy
| | - M. Caruso
- Division of Veterinary Pharmacology and Toxicology; Department of Veterinary Medicine; University of Bari; Valenzano Bari Italy
| | - S. Punzi
- Division of Veterinary Pharmacology and Toxicology; Department of Veterinary Medicine; University of Bari; Valenzano Bari Italy
| | - G. Crescenzo
- Division of Veterinary Pharmacology and Toxicology; Department of Veterinary Medicine; University of Bari; Valenzano Bari Italy
| | | | - C. Belloli
- Division of Veterinary Pharmacology and Toxicology; Department of Veterinary Medicine; University of Bari; Valenzano Bari Italy
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Gauff FC, Patan-Zugaj B, Licka TF. Effect of short-term hyperinsulinemia on the localization and expression of endothelin receptors A and B in lamellar tissue of the forelimbs of horses. Am J Vet Res 2014; 75:367-74. [PMID: 24669922 DOI: 10.2460/ajvr.75.4.367] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
OBJECTIVE To determine the effect of short-term hyperinsulinemia on the localization and expression of endothelin receptor (ETR)-A and ETR-B in lamellar tissue of the forelimbs of horses. SAMPLES Distal portion of 15 cadaveric forelimbs from healthy adult horses (1 limb/horse) obtained immediately after slaughter at an abattoir. PROCEDURES Each forelimb was assigned to 1 of 3 treatment groups (perfused with autologous blood for 10 hours [control perfusion; n = 5], perfused with an insulin [142 ± 81 μU/mL] perfusate for 10 hours [insulinemic perfusion; 5], or not perfused [unperfused control; 5]). Immunohistochemical evaluation of lamellar tissue was performed to assess localization of ETR-A and ETR-B. Expression of ETR-A and ETR-B was measured semiquantitatively on a scale of 0 to 3 (0 = none, 1 = mild, 2 = moderate, and 3 = high-intensity staining) and quantitatively by means of gray value analysis with imaging software. RESULTS In all specimens, ETR-A and ETR-B were localized in endothelium, smooth muscle cells, axons, and keratinocytes. Quantitative expression of ETR-A in the midportion of the primary epidermal lamellae for the insulinemic perfusion group (149 ± 16) was lower than that for the control perfusion group (158 ± 15). Expression of ETR-B in the primary epidermal lamellae tips for the insulinemic perfusion group (140 ± 29) was higher than that for the control perfusion group (114 ± 8). CONCLUSIONS AND CLINICAL RELEVANCE Hyperinsulinemia caused significant changes in endothelin receptor expression, which suggested that ETR antagonists might be beneficial for treatment of laminitis in horses.
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Affiliation(s)
- Felicia C Gauff
- Department of Horses and Small Animals, University of Veterinary Medicine Vienna, A-1210 Vienna, Austria
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Venugopal C, Holmes E, Beadle R, Kearney M, Eades S. Comparison of Insulin-Induced Digital Vessel Ring Responses of Laminitic and Clinically Healthy Horses. J Equine Vet Sci 2014. [DOI: 10.1016/j.jevs.2014.05.008] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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Wooldridge AA, Waguespack RW, Schwartz DD, Venugopal CS, Eades SC, Beadle RE. Vasorelaxation responses to insulin in laminar vessel rings from healthy, lean horses. Vet J 2014; 202:83-8. [PMID: 25155219 DOI: 10.1016/j.tvjl.2014.07.021] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2013] [Revised: 07/21/2014] [Accepted: 07/25/2014] [Indexed: 10/25/2022]
Abstract
Hyperinsulinemia causes laminitis experimentally and is a risk factor for naturally occurring laminitis. The aim of this study was to investigate the effects of insulin on laminar vascular relaxation and to induce insulin-associated vascular dysfunction in vitro. Relaxation responses of isolated laminar arterial and venous rings to acetylcholine and insulin were evaluated. To alter vascular function in response to insulin, all vessel rings were incubated with insulin or vehicle, submaximally contracted, administered insulin again and relaxation responses recorded. Laminar arteries were also incubated with the mitogen-activated protein kinase (MAPK) inhibitor, PD-98059. Relaxation in response to acetylcholine was not different between arteries and veins, but veins relaxed less in response to insulin than arteries. In arteries incubated with insulin, the subsequent relaxation response to insulin was blunted. Veins had minimal relaxation to insulin regardless of incubation. Arteries incubated with PD-98059 relaxed more in response to insulin than arteries not exposed to PD-98059, indicating that MAPK plays a role in maintenance of basal tone in laminar arteries. A differing response of laminar veins and arteries to insulin-induced relaxation may be important in understanding the link between hyperinsulinemia and laminitis. In vitro induction of vascular dysfunction in response to insulin in laminar arteries may be useful for testing therapeutic interventions and for understanding the pathophysiology of laminitis.
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Affiliation(s)
- A A Wooldridge
- Department of Clinical Sciences, Auburn University College of Veterinary Medicine, 1500 Wire Road, Auburn, Alabama 36849, USA.
| | - R W Waguespack
- Southeastern Veterinary Surgery Center, 3576 Macon Rd., Columbus, Georgia 31907, USA
| | - D D Schwartz
- Department of Anatomy, Physiology, and Pharmacology, Auburn University College of Veterinary Medicine, 1500 Wire Road, Auburn, Alabama 36849, USA
| | - C S Venugopal
- Equine Health Studies Program, Louisiana State University School of Veterinary Medicine, Skip Bertman Drive, Baton Rouge, Louisiana 70803, USA
| | - S C Eades
- Equine Health Studies Program, Louisiana State University School of Veterinary Medicine, Skip Bertman Drive, Baton Rouge, Louisiana 70803, USA
| | - R E Beadle
- Equine Health Studies Program, Louisiana State University School of Veterinary Medicine, Skip Bertman Drive, Baton Rouge, Louisiana 70803, USA
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Lapo RA, Gogny M, Chatagnon G, Lalanne V, Harfoush K, Assane M, Desfontis JC, Mallem MY. Equine digital veins are more sensitive to superoxide anions than digital arteries. Eur J Pharmacol 2014; 740:66-71. [PMID: 25014758 DOI: 10.1016/j.ejphar.2014.06.016] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2013] [Revised: 06/16/2014] [Accepted: 06/17/2014] [Indexed: 11/24/2022]
Abstract
This work was designed to investigate (i) the effect of superoxide dismutase (SOD) inhibition on endothelial function and (ii) the free radical-induced endothelial dysfunction in equine digital veins (EDVs) and equine digital arteries (EDAs) isolated from healthy horses. EDV and EDA rings were suspended in a 5 ml organ bath containing Krebs solution. After a 60 min equilibration period, EDV and EDA rings were contracted with phenylephrine. Then, cumulative concentration-response curves (CCRCs) to acetylcholine were performed. In both EDVs and EDAs, acetylcholine (1 nM to 10 µM) produced concentration-dependent relaxation. We investigated the influence of SOD inhibition by diethyldithiocarbamate (DETC; 100 µM), a CuZnSOD inhibitor, on EDAs and EDVs relaxant responses to acetylcholine. Acetylcholine -mediated relaxation was impaired by DETC only in EDVs. SOD activity assayed by a xanthine-xanthine oxidase method was higher in EDAs compared with EDVs (P<0.05). CCRCs to acetylcholine established in the presence of pyrogallol (30 µM) or homocysteine (20 µM), two superoxide anions generating systems showed that in both EDVs and EDAs, the acetylcholine-mediated relaxation was significantly impaired by pyrogallol and homocysteine. This impairment was more pronounced in EDVs than in EDAs. Moreover, the pyrogallol-induced impairment of acetylcholine-mediated relaxation was potentiated by DETC to a greater extent in EDVs. We concluded that due to the lower activity of SOD, EDVs are more sensitive to superoxide anions than EDAs. So, any alteration of superoxide anions metabolism is likely to have a more important impact on venous rather than arterial relaxation.
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Affiliation(s)
- Rock Allister Lapo
- Ecole Inter-états des Sciences et Médecine Vétérinaires BP 5077 Dakar, Senegal
| | - Marc Gogny
- LUNAM Université, Oniris, UPSP 5304 de Physiopathologie Animale et Pharmacologie Fonctionnelle, Atlanpole La Chantrerie, BP 40706, Nantes F-44307, France
| | - Gérard Chatagnon
- LUNAM Université, Oniris, Unité de Sécurité Sanitaire des Biotechnologies de la Reproduction, Atlanpole La Chantrerie, BP 40706, Nantes, F-44307, France
| | - Valérie Lalanne
- LUNAM Université, Oniris, UPSP 5304 de Physiopathologie Animale et Pharmacologie Fonctionnelle, Atlanpole La Chantrerie, BP 40706, Nantes F-44307, France
| | - Khaled Harfoush
- LUNAM Université, Oniris, UPSP 5304 de Physiopathologie Animale et Pharmacologie Fonctionnelle, Atlanpole La Chantrerie, BP 40706, Nantes F-44307, France
| | - Moussa Assane
- Ecole Inter-états des Sciences et Médecine Vétérinaires BP 5077 Dakar, Senegal
| | - Jean-Claude Desfontis
- LUNAM Université, Oniris, UPSP 5304 de Physiopathologie Animale et Pharmacologie Fonctionnelle, Atlanpole La Chantrerie, BP 40706, Nantes F-44307, France
| | - Mohamed Yassine Mallem
- LUNAM Université, Oniris, UPSP 5304 de Physiopathologie Animale et Pharmacologie Fonctionnelle, Atlanpole La Chantrerie, BP 40706, Nantes F-44307, France.
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Walsh D, Collins S, Winterford C, Pollitt C. The equine foot lamellar lymphatic system. J Equine Vet Sci 2013. [DOI: 10.1016/j.jevs.2013.08.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Katz LM, Bailey SR. A review of recent advances and current hypotheses on the pathogenesis of acute laminitis. Equine Vet J 2013; 44:752-61. [PMID: 23106629 DOI: 10.1111/j.2042-3306.2012.00664.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
With the increasing number of studies being published on the different experimental models used to induce and study acute laminitis, the pathophysiological events associated with these various models (i.e. starch overload, oligofructose overload, black walnut extract and hyperinsulinaemia) can be compared more realistically. Within this review, the mechanisms for metabolic vs. inflammatory laminitis are discussed, and the question of how pasture laminitis may fit into any of the proposed mechanisms is addressed.
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Affiliation(s)
- L M Katz
- School of Veterinary Medicine, University College Dublin, Dublin, Ireland.
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Towards a new treatment for equine acute laminitis: The importance of signalling pathways. Vet J 2012; 192:258-9. [DOI: 10.1016/j.tvjl.2011.10.011] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2011] [Accepted: 10/15/2011] [Indexed: 11/19/2022]
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Venugopal CS, Eades S, Holmes EP, Beadle RE. Insulin resistance in equine digital vessel rings: an in vitro model to study vascular dysfunction in equine laminitis. Equine Vet J 2011; 43:744-9. [PMID: 21496102 DOI: 10.1111/j.2042-3306.2010.00351.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
REASONS FOR PERFORMING STUDY One of the causes of equine laminitis is hyperinsulinaemia, which may be associated with endothelial dysfunction and insulin resistance of vessels. HYPOTHESIS AND OBJECTIVES Insulin resistance can be induced in palmar digital vessels by continued exposure to insulin in vitro. The objective was to evaluate this in vitro model for future studies. METHODS Palmar digital vessel segments were collected immediately after euthanasia from horses with normal insulin/glucose blood values. Four arterial and 4 venous rings (3 mm wide) were prepared and each ring mounted in a tissue bath, containing Tyrode's solution at 37°C, 2 g tension was applied and the rings allowed to equilibrate for 45 min. Of the 4 rings of each vessel type, one was used as a control. One each of the remaining 3 rings was used for incubation with insulin (to induce resistance), wortmannin (to block PI3-kinase) and PD-098059 (to block MAP-kinase), respectively, for 30 min. After the incubation period, the rings were contracted with phenylephrine. When the response reached a plateau, a single dose of insulin was added to the baths and the response of each ring monitored for 30 min. RESULTS Insulin relaxed the control rings and those treated with PD 098059 but contracted those pretreated with insulin and wortmannin. Normal relaxation responses of the rings were converted to contractions by insulin resistance. Insulin resistance was confirmed by the qualitative response of insulin-incubated and wortmannin-incubated rings. CONCLUSIONS This study demonstrated successful induction of insulin resistance in both arterial and venous rings. It also suggested that the MAP-kinase pathway plays a minor role in controlling vasomotor tone under normal physiological conditions. POTENTIAL RELEVANCE The study suggests that the induction of insulin resistance in equine palmar digital vessel rings is reliable and provides a good in vitro model for studying the vascular insulin resistance which may occur in equine laminitis.
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Affiliation(s)
- C S Venugopal
- Equine Health Studies Program, Department of Veterinary Clinical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA, USA.
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Divers TJ. Clinical Application of Current Research Findings Toward the Prevention and Treatment of Acute Laminitis in Horses With Systemic Inflammatory Diseases: An Internist’s Perspective. J Equine Vet Sci 2010. [DOI: 10.1016/j.jevs.2010.07.021] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Tóth F, Frank N, Chameroy KA, Bostont RC. Effects of endotoxaemia and carbohydrate overload on glucose and insulin dynamics and the development of laminitis in horses. Equine Vet J 2010; 41:852-8. [PMID: 20383981 DOI: 10.2746/042516409x479027] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
REASONS FOR PERFORMING STUDY Insulin resistance (IR) is a risk factor for pasture-associated laminitis in equids and alimentary carbohydrate overload may trigger laminitis. Whether glucose metabolism responses to carbohydrate overload are more pronounced in insulin-resistant horses requires further study. HYPOTHESIS Horses pretreated with endotoxin to alter insulin sensitivity differ significantly in their glucose and insulin responses to carbohydrate overload. METHODS Horses (n=24) were divided into 3 groups. A lipopolysaccharide (LPS; n=8) group that received endotoxin as an 8 h 7.5 ng/kg bwt/h i.v. continuous rate infusion, an oligofructose (OF; n=8) group that received an infusion of saline followed by 5 g/kg bwt OF via nasogastric intubation, and a LPS/OF (n=8) group that received LPS followed 16 h later by OF. Glucose and insulin dynamics were evaluated at -24 h and 48 h using the frequently sampled i.v. glucose tolerance test and minimal model analysis. Physical examinations and haematology were performed and the severity of laminitis assessed. RESULTS Horses receiving LPS developed leucopenia and both LPS and OF induced clinical signs consistent with systemic inflammation. Insulin sensitivity significantly decreased (P < 0.001) over time, but responses did not differ significantly among groups. Time (P < 0.001) and treatment x time (P = 0.038) effects were detected for the acute insulin response to glucose, with mean values significantly increasing in LPS and LPS/OF groups, but not the OF group. Five horses in the LPS/OF group developed clinical laminitis compared with 0 and 2 horses in the LPS and OF groups, respectively. CONCLUSIONS Endotoxaemia and carbohydrate overload reduce insulin sensitivity in horses. Endotoxin pretreatment does not affect the alterations in glucose metabolism induced by carbohydrate overload. POTENTIAL RELEVANCE Insulin sensitivity decreases after carbohydrate overload in horses, which may be relevant to the development of pasture-associated laminitis.
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Affiliation(s)
- F Tóth
- Department of Large Animal Clinical Sciences, College of Veterinary Medicine, University of Tennessee, Knoxville, Tennessee 37996, USA
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Patan B, Budras KD, Licka TF. Effects of long-term extracorporeal blood perfusion of the distal portion of isolated equine forelimbs on metabolic variables and morphology of laminar tissue. Am J Vet Res 2009; 70:669-77. [PMID: 19405908 DOI: 10.2460/ajvr.70.5.669] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVE To establish an ex vivo model of blood perfusion in the distal portion of isolated equine forelimbs that closely represents the in vivo situation in the laminar tissue of the hoof. SAMPLE POPULATION 18 forelimbs collected from 9 healthy adult horses following slaughter at a licensed abattoir. PROCEDURES The distal portion of isolated equine forelimbs from 9 horses were perfused under physiologic conditions over a period of 6, 8, and 10 hours with autologous blood. To determine cell viability in perfused tissues, indicators for metabolism (lactate generation and glucose and oxygen consumption) as well as indicators for cell damage (potassium concentration and lactate dehydrogenase activity) were examined at 1-hour intervals from samples of the perfusate. Weight gain in the forelimb was used to determine the edema index. After perfusion, light and electron microscopic examinations of laminar tissue specimens were performed. RESULTS During hemoperfusion of the isolated forelimbs, mean +/- SD glucose consumption was 197.4 +/- 65.1 mg/h, lactate generation was 1.84 +/- 0.79 mmol/h, and oxygen consumption was 6.4 x 10(-6) +/- 8.9 x 10(-5) mL.g(-1).min(-1). Neither an efflux of potassium into the perfusate nor a relevant increase of the lactate dehydrogenase activity was detected, indicating low amounts of cellular damage in the perfused tissues. Weight gain of forelimbs was 1.02 +/- 0.95%. Histologic and ultrastructural appearance of the laminar tissue revealed no signs of tissue damage. CONCLUSIONS AND CLINICAL RELEVANCE Isolated equine limbs were perfused under physiologic conditions over a period of < or = 10 hours without structural damage to the laminar tissue.
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Affiliation(s)
- Bianca Patan
- Clinic of Orthopaedics in Large Animals, Department of Horses and Small Animals, Vienna University of Veterinary Medicine, A-1210 Vienna, Austria
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Robertson TP, Bailey SR, Peroni JF. Equine laminitis: A journey to the dark side of venous. Vet Immunol Immunopathol 2009; 129:164-6. [DOI: 10.1016/j.vetimm.2008.11.015] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Martins Filho L, Fagliari J, Moraes J, Sampaio R, Oliveira J, Lacerda Neto J. Influência da heparina sódica na ocorrência de laminite eqüina induzida por sobrecarga de carboidratos. ARQ BRAS MED VET ZOO 2008. [DOI: 10.1590/s0102-09352008000600009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Avaliou-se a eficiência da infusão intravenosa de heparina sódica (100UI/kg/8h, a partir de 24h após o fornecimento de carboidrato, até completar 48h) no controle da laminite eqüina experimentalmente induzida por sobrecarga de carboidrato (17,6g de amido de milho/kg de peso corpóreo). Foram utilizados 15 eqüinos adultos, distribuídos em três grupos experimentais: GI (grupo-controle); GII (grupo laminite) e GIII (grupo laminite+heparina). Posteriormente ao fornecimento de carboidrato, os animais foram submetidos a exames físicos e laboratoriais durante um período de 48 horas. Ao final do experimento, os animais foram submetidos à eutanásia pela aplicação intravenosa de 5ml de maleato de acepromazina seguida de 1g de tiopental sódico e 1 litro de solução saturada de KCl para a obtenção de amostras de tecidos dos cascos, necessárias ao exame histológico. Os animais de GII e GIII, submetidos à sobrecarga de carboidratos, desenvolveram laminite, exibindo claudicação 12 e 24h após o fornecimento de carboidrato, respectivamente, bem como aumentos da freqüência cardíaca e do tempo de preenchimento capilar. As alterações histológicas, semelhantes em GII e GIII, eram do tipo degenerativo, como adelgaçamento de lâminas epidérmicas, retração, achatamento e deslocamento de lâminas dérmicas, vacuolização epidérmica e desorganização do tecido epidérmico. A infusão da heparina sódica não preveniu ou atenuou a degeneração laminar.
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Controlling the equine neutrophil: A generator of devastating tissue damage during equine inflammatory disease. Vet J 2008; 178:3-4. [DOI: 10.1016/j.tvjl.2008.01.010] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2008] [Revised: 01/21/2008] [Accepted: 01/21/2008] [Indexed: 11/23/2022]
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Evaluation of equine laminar vein function: harvesting, dissection and the use of functional methods to distinguish between veins and arteries. J Pharmacol Toxicol Methods 2008; 57:92-9. [PMID: 18280185 DOI: 10.1016/j.vascn.2007.10.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2007] [Accepted: 10/11/2007] [Indexed: 11/23/2022]
Abstract
INTRODUCTION Pharmacological evaluation of the unique equine laminar microvasculature is crucial to understanding its role in health and in diseases such as laminitis. However, separating the distinctive characteristics of arterial versus venous components of this complex vascular network has previously proved to be extremely difficult. Encased in a hard hoof capsule, isolation of individual blood vessels presents a considerable challenge. Exacerbating this difficulty, the laminar venous network is adapted to sustain high intravascular pressures and consequently has thickened walls, making the normally straightforward visual distinction between arteries and veins problematic. Here we describe a novel harvesting and dissection method coupled with a functional analysis procedure that facilitates distinction of arteries and veins. METHODS Laminar tissue was recovered from the hoof of euthanized, clinically normal horses by dissection at the coronary band and stored in cold Krebs-Henseleit physiological salt solution prior to further dissection in the laboratory to remove 2 mm segments of vessels 100-500 microm in diameter. Active length tension measurements were made to evaluate optimal conditions for experimentation, and based on the differences in contractility and appearance, an experimental protocol was set up to allow a) initial distinction between arteries and veins and b) in vitro pharmacological evaluation. RESULTS Active length tension studies clearly revealed the presence of two populations of vessels distinguished by either a large or a lower maximal contraction that subsequent histological evaluation confirmed to be arteries and veins respectively. Functional distinction using relative contractility to 60 mM potassium salt solution then demonstrated equine laminar veins to have increased sensitivity to the agonist endothelin 1 (ET-1) compared to arteries. DISCUSSION In vitro evaluation of laminar vessels is possible despite anatomical obstacles. Furthermore, a clear distinction can be made between laminar veins and arteries using functional characteristics providing vessels of a similar size range are selected. Utilising these novel procedures, investigators can unambiguously analyse the pharmacological characteristics of equine laminar veins and arteries to decipher the physiological mechanisms responsible for the control of laminar blood flow.
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Robertson TP, Moore JN, Noschka E, Lewis TH, Lewis SJ, Peroni JF. Effects of Rho-kinase and Src protein tyrosine kinase inhibition on agonist-induced vasoconstriction of arteries and veins of the equine laminar dermis. Am J Vet Res 2007; 68:886-94. [PMID: 17669029 DOI: 10.2460/ajvr.68.8.886] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVE To determine the effects of inhibition of Rho-kinase or Src-family protein tyrosine kinases (srcPTK) on agonist-induced contractile responses in equine laminar arteries and veins. SAMPLE POPULATION Laminar arteries and veins obtained from 13 adult mixed-breed horses. PROCEDURES Laminar vessels were mounted on myographs and exposed to phenylephrine (PE), 5-hydroxytryptamine (5-HT), prostaglandin F(2) (PGF(2)), and endothelin-1 (ET-1) with or without the Rho-kinase inhibitor Y-27632 (10 microM), srcPTK inhibitor PP2 (10 microM), or a negative control analogue for PP2 (PP3; 10 microM). RESULTS Responses to PE were reduced by use of Y-27632 in laminar vessels (approx inhibition, 55%). However, Y-27632 reduced responses to 5-HT to a greater degree in veins than in arteries (approx inhibition of 55% and 35%, respectively). The Y-27632 also reduced responses of laminar veins to ET-1 by approximately 40% but had no effect on maximum responses of laminar arteries to ET-1, although a rightward shift in the concentration response curve was evident. Addition of PP2 reduced responses to PE, 5-HT, and PGF(2) in laminar veins by approximately 40%, 60%, and 65%, respectively, compared with responses after the addition of PP3; PP2 had no effect on responses to ET-1. In laminar arteries, PP2 reduced 5-HT-induced contractions by approximately 50% but did not affect responses to PE or ET-1. CONCLUSIONS AND CLINICAL RELEVANCE Results of the study were consistent with activation of Rho-kinase being important during agonist-induced constriction in laminar vessels, activation of srcPTK being an agonist-dependent event, and more prominent roles for Rhokinase and srcPTK in veins than in arteries.
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Affiliation(s)
- Tom P Robertson
- Department of Physiology and Pharmacology, Institute of Comparative Medicine, College of Veterinary Medicine, University of Georgia, Athens, GA 30602-7389, USA
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Peroni JF, Moore JN, Noschka E, Lewis TH, Lewis SJ, Robertson TP. Effect of voltage-gated and capacitative calcium entry blockade on agonist-induced constriction of equine laminar blood vessels. Am J Vet Res 2007; 68:722-9. [PMID: 17605607 DOI: 10.2460/ajvr.68.7.722] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVE To characterize the relative contributions of voltage-gated and capacitative Ca(2+) entry to agonist-induced contractions of equine laminar arteries and veins. ANIMALS 16 adult mixed-breed horses. PROCEDURES Laminar arteries and veins were isolated and mounted on small vessel myographs for the measurement of isometric tension. Concentration-response curves were obtained for the vasoconstrictor agonists phenylephrine, 5-hydroxytryptamine (5-HT), prostaglandin F(2) (PGF(2)), and endothelin-1 (ET-1) either in the absence of extracellular Ca(2+) or in the presence of the voltage-gated Ca(2+) channel inhibitor diltiazem or the putative inhibitor of capacitative Ca(2+) entry, trifluoromethylphenylimidazole. RESULTS In the absence of extracellular Ca(2+), maximal responses of veins to 5-HT, phenylephrine, ET-1 and PGF(2) were reduced by 80%, 50%, 50%, and 45%, respectively; responses of arteries to 5-HT, phenylephrine, and ET-1 were reduced by 95%, 90%, and 20%, respectively. Although diltiazem did not affect the maximal responses of veins to any agonist, responses of arteries to 5-HT, phenylephrine, and ET-1 were reduced by 40%, 50%, and 27%, respectively. Trifluoromethylphenylimidazole did not affect maximal responses of veins, but did reduce their contractile responses to low concentrations of ET-1 and PGF(2). CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that the contribution of extracellular Ca(2+) to laminar vessel contractile responses differs between arteries and veins and also between contractile agonists, voltage-gated Ca(2+) entry is more predominant in laminar arteries than in veins, and capacitative Ca(2+) entry has a minor role in agonist-induced contractile responses of laminar veins.
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Affiliation(s)
- John F Peroni
- Department of Physiology and Pharmacology, Institute of Comparative Medicine, College of Veterinary Medicine, University of Georgia, Athens, GA 30602-7389, USA
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Robertson TP, Moore JN, Noschka E, Lewis TH, Lewis SJ, Peroni JF. Evaluation of activation of protein kinase C during agonist-induced constriction of veins isolated from the laminar dermis of horses. Am J Vet Res 2007; 68:664-9. [PMID: 17542701 DOI: 10.2460/ajvr.68.6.664] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVE To determine the effects of the protein kinase C (PKC) inhibitor, Ro-31-8220, on agonist-induced constriction of laminar arteries and veins obtained from horses. SAMPLE POPULATION Laminar arteries and veins obtained from 8 adult mixed-breed horses. PROCEDURES Laminar arteries and veins were isolated and mounted on small vessel myographs for the measurement of isometric tension. Concentration-response curves were then obtained for the vasoconstrictor agonists phenylephrine, 5-hydroxytryptamine, prostaglandin F(2), and endothelin-1. All responses were measured with or without the addition of Ro-31-8220 (3 microM). RESULTS Laminar veins were more sensitive to vasoconstrictor agonists than laminar arteries, and incubation of laminar veins with Ro-31-8220 resulted in significantly smaller agonist-induced contractile responses for all agonists tested. In contrast, Ro-31-8220 had no effect on agonist-induced contractile responses of laminar arteries. CONCLUSIONS AND CLINICAL RELEVANCE Results of the study were consistent with activation of PKC being confined to agonist-induced contraction of laminar veins isolated from the laminar dermis of horses. Consequently, the possible involvement of PKC in the venoconstriction observed during the development of laminitis is worthy of further investigation.
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Affiliation(s)
- Tom P Robertson
- Department of Physiology and Pharmacology, Institute of Comparative Medicine, College of Veterinary Medicine, University of Georgia, Athens, GA 30602-7389, USA
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Bailey SR, Elliott J. The corticosteroid laminitis story: 2. Science of if, when and how. Equine Vet J 2007; 39:7-11. [PMID: 17228587 DOI: 10.2746/042516407x166035] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Affiliation(s)
- S R Bailey
- Department of Veterinary Basic Sciences, Royal Veterinary College, London, UK
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Eades SC, Stokes AM, Johnson PJ, LeBlanc CJ, Ganjam VK, Buff PR, Moore RM. Serial alterations in digital hemodynamics and endothelin-1 immunoreactivity, platelet-neutrophil aggregation, and concentrations of nitric oxide, insulin, and glucose in blood obtained from horses following carbohydrate overload. Am J Vet Res 2007; 68:87-94. [PMID: 17199424 DOI: 10.2460/ajvr.68.1.87] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVE To quantify changes in endothelium-derived factors and relate those changes to various aspects of digital hemodynamics during the prodromal stages of carbohydrate overload (CHO)-induced laminitis in horses. ANIMALS 20 adult horses without abnormalities of the digit. PROCEDURES Digital and jugular venous blood samples were collected at 1-hour intervals (for assessment of endothelin-1 [ET-1] immunoreactivity and measurement of glucose, insulin, and nitric oxide [NO] concentrations) or 4-hour intervals (CBC and platelet-neutrophil aggregate assessment) for 8 hours or 16 hours after induction of CHO-associated laminitis in horses treated with an ET-1 antagonist. Effects of treatment, collection site, and time and the random effects of horse on each variable were analyzed by use of a repeated-measures model. Where treatment and collection site had no significant effect, data were combined. RESULTS Compared with baseline values, CHO resulted in changes in several variables, including a significant increase from baseline in digital blood ET-like immunoreactivity at 11 hours; digital blood ET-like immunoreactivity was significantly greater than that in jugular venous blood at 8, 9, 11, and 12 hours. Digital and jugular venous blood concentrations of glucose increased from baseline significantly at 3, 4, and 5 hours; insulin concentration increased significantly at 5 hours; and the number of platelet-neutrophil aggregates increased significantly at 12 hours. CONCLUSIONS AND CLINICAL RELEVANCE In horses, concurrent increases in venous blood ET-1 immunoreactivity, insulin and glucose concentrations, and platelet-neutrophil aggregates support a role of endothelial dysfunction in the pathogenesis of CHO-induced laminitis.
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Affiliation(s)
- Susan C Eades
- Equine Health Studies Program, Department of Veterinary Clinical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803, USA
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