Urea Clearance: A New Technique Based on Microdialysis to Assess Liver Blood Flow Studied in a Pig Model of Ischemia/Reperfusion

Farnebo, Simon; Winbladh, Anders; Zettersten, Erik; Sandström, Per; Gullstrand, Per; Samuelsson, Kersti; Theodorson, E.; Sjöberg, Folke

doi:10.1159/000319868

Cited by 7 publications

(16 citation statements)

References 57 publications

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“…This paper, we believe, further verifies previous data that suggested that urea clearance is a reliable tool for detecting fluctuations in blood flow in rat skeletal muscle and porcine liver [8,10]. Previous comparisons with the established and validated ethanol technique in microdialysis further strengthen our evidence of the ability of the urea clearance technique to reliably and reproducibly assess blood flow.…”

Section: Discussionsupporting

confidence: 86%

Assessment of Blood Flow Changes in Human Skin by Microdialysis Urea Clearance

Farnebo¹,

Zettersten²,

Samuelsson

et al. 2011

Microcirculation

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Urea clearance can be used as a relatively simple method to estimate blood flow changes during microdialysis of vasoactive substances, in particular when the tissue is preconditioned in order to enhance the contrast between baseline and the responses to the provocations. Our results support that, in the model described, urea clearance was superior to the optical methods as it detected both the increases and decrease in blood flow, and the returns to baseline between these periods.

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Section: Discussionsupporting

confidence: 86%

Assessment of Blood Flow Changes in Human Skin by Microdialysis Urea Clearance

Farnebo¹,

Zettersten²,

Samuelsson

et al. 2011

Microcirculation

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“…In principle, this setup mimicked standard brain studies in small animals and provided an alternative to keeping the rats restrained [ 15 ]. Perfusate A composition, the rate of medium flow and sampling pattern respected earlier recommendations [ 21 , 29 ] and took into account our current analytical requirements. The duration of the study and the collection of specimens with focus on day 4 followed from the optimum time window between post-operative animal recovery and spatial development of foreign body reaction as reported by Mou et al .…”

Section: Discussionmentioning

confidence: 99%

“…Selected conventional analytes (glucose, lactate and urea) were employed to assess local microcirculation and provide some insight into probe function [ 8 , 20 , 21 ], although dynamic changes of submucosal metabolite recovery as long as four days following surgical probe implantation have not been described in rodents thus far. The present study shows that glucose and lactate-to-glucose ratio generally follow opposing trends with the former decreasing and the latter growing as soon as two to three days after surgery ( Fig 2 ).…”

Section: Discussionmentioning

confidence: 99%

“…as a convenient measure of local blood flow in a number of organs including the muscle, the skin or the liver [ 21 , 27 , 38 ]. Even though these authors found significant correlation between urea and lactate in the liver [ 21 ], the changes in the levels of urea during blood flow reduction were much less prominent (a typical increment of 10 to 30%) compared to the classical metabolic parameters or their ratios [ 20 ]. In the present study, the absolute concentrations of urea as well as RD urea are displayed in Fig 2D .…”

Section: Discussionmentioning

confidence: 99%

“…Such practice might lead, besides high resolution metabolic or pharmacokinetic profiles, also to a reduction of the number of experimental subjects. Based on simple diffusion, the catheter allows continuous delivery or withdrawal of metabolites [ 19 , 20 ], molecules related to cellular damage [ 2 ], markers of intestinal permeability [ 2 , 3 ], blood flow indicators [ 20 , 21 ], signaling molecules [ 15 , 22 ], medications [ 23 ], or different (tracer-labelled) internal standards used for calibration purposes [ 24 ]. Thus, if successfully applied in the gut of awake rodents, microdialysis-based sensors might prove advantageous for various priorities in experimental animal research.…”

Section: Introductionmentioning

confidence: 99%

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Critical evaluation of colon submucosal microdialysis in awake, mobile rats

et al. 2018

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Sensors able to record large bowel physiology and biochemistry in situ in awake rodents are lacking. Microdialysis is a mini-invasive technique that may be utilized to continuously deliver or recover low-molecular substances from various tissues. In this experiment we evaluated the feasibility of in vivo microdialysis to monitor extracellular fluid chemistry in the descending colon submucosa of conscious, freely moving rodents. Following surgical implantation of a microdialysis probe, male Wistar rats were housed in metabolic cages where they were analgized and clinically followed for four days with free access to standard diet and water. To assess local microcirculation and probe function, glucose, lactate, glucose-to-lactate ratio and urea clearance were determined in the dialysates from the three postoperative days with focus on the final 24-h period. In an attempt to mitigate the expected tissue inflammatory response, one group of animals had the catheters perfused with 5-aminosalicylic acid-enriched medium with final concentration 1 μmol/L. For verification of probe position and the assessment of the surrounding foreign body reaction, standard histological and immunohistochemical methods were employed. Microdialysis of rat gut is associated with considerable technical challenges that may lead to the loss of probe function and high drop-out rate. In this setting, limited data did not allow to draw any firm conclusion regarding local anti-inflammatory effectiveness of 5-aminosalicylic acid perfusion. Although intestinal microdialysis may be suitable for larger anesthetized animals, low reproducibility of the presented method compromises its routine experimental use in awake and freely moving small-sized rodents.

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Lamellar energy metabolism and perfusion in the euglycaemic hyperinsulinaemic clamp model of equine laminitis

Stokes

Bertin

Stefanovski

et al. 2020

Equine Veterinary Journal

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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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Urea Clearance: A New Technique Based on Microdialysis to Assess Liver Blood Flow Studied in a Pig Model of Ischemia/Reperfusion

Cited by 7 publications

References 57 publications

Assessment of Blood Flow Changes in Human Skin by Microdialysis Urea Clearance

Assessment of Blood Flow Changes in Human Skin by Microdialysis Urea Clearance

Critical evaluation of colon submucosal microdialysis in awake, mobile rats

Lamellar energy metabolism and perfusion in the euglycaemic hyperinsulinaemic clamp model of equine laminitis

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