scholarly journals Variation of Red Blood Cell Rheology and Adhesiveness during Vaso-Occlusive Crises in Sickle Cell Patients

Blood ◽  
2016 ◽  
Vol 128 (22) ◽  
pp. 1311-1311
Author(s):  
Regine Hierso ◽  
Claudine Lapoumeroulie ◽  
Philippe Connes ◽  
Sara El Hoss ◽  
Catia Oliveira ◽  
...  
Keyword(s):  
Emergency Department ◽  
Steady State ◽  
Blood Cell ◽  
Sickle Cell ◽  
Red Blood Cell ◽  
Blood Viscosity ◽  
Rheological Parameters ◽  
Positive Correlation ◽  
Rbc Aggregation ◽  
Rbc Deformability

Abstract Introduction: Impaired red blood cell (RBC) rheology, increased RBC adhesiveness to the vascular wall, enhanced inflammation and blunted vascular reactivity are involved in the pathophysiology of sickle cell anemia (SCA). Painful vaso-occlusive crisis (VOC) is the most frequent complication encountered by SCA patients. While several studies compared several biomarkers of severity between patients at steady state and others during VOC, very few works compared the same patients in the two conditions. It is therefore difficult to know what happens during VOC. The present study was devoted to compare several hematological, biochemical, and rheological parameters, as well as RBC adhesiveness at steady state and during VOC. Altogether, 36 SCA patients were studied. Methods: This prospective monocentric study was performed at the University Hospital of Pointe-a-Pitre (Guadeloupe, French West Indies), in accordance with the guidelines set by the declaration of Helsinki and was approved by the Regional Ethics Committee (CPP Sud/Ouest Outre Mer III, Bordeaux, France, registration number: 2012-A00701-42). After admission to the emergency department for a VOC episode, patients were informed about the purpose and procedures of the study and gave their written consent. Blood was sampled at the arrival of the patients at the emergency department before they received any medications. A visit to the Sickle Cell Center was then scheduled at least 3 months after the emergency department admission to collect routine blood samples at steady state. Steady state condition was defined as a period free of blood transfusion in the previous three months and without any acute SCA complications in the previous two months. RBC deformability was determined at 3 and 30 Pa by ektacytometry (LORRCA, Mechatronics), RBC aggregation properties (RBC aggregation and RBC disaggregation threshold) by syllectometry (LORRCA), blood viscosity by cone-plate viscosimetry (Brookfield, DVII+ model with CPE 40 spindle) at 225 s-1. Irreversible sickle cells (ISCs) were measured on an Imagestream ISX MkII flow cytometer (Amnis Corp, EMD Millipore). Lu/BCAM, ICAM-4/Lw and the alpha4-beta1 integrin were measured by flow cytometry at the RBC surface (FACSCanto II, BD Biosciences). RBC adhesion to monolayers of transformed human bone marrow endothelial cells (TrHBMECs) was studied in continuous flow conditions in Vena8 Endothelial+ Biochips (Cellix Ltd). Other hematological and biochemical parameters were measured by standard techniques. Results: Compared to steady state values, white blood cell (9.2 [6.7-10.6] versus 12.3 [10.1-16.2] 109/L, p < 0.001) and C-Reactive Protein (3.7 [3.3-6.0] versus 7.1 [3.3-17.5] mg/L, p < 0.05) levels increased during VOC (table 1). Lactate dehydrogenase level slightly increased during VOC (418 [351-564] versus 437 [370-727] IU/L, p < 0.03) but no change was observed for hemoglobin. RBC deformability slightly decreased during VOC (0.34 [0.26-0.44]) compared to steady state (0.38 [0.31-0.46], p < 0.02). RBC aggregation increased during VOC (55 [46-60 %] compared to steady state (51 [46-54] %, p < 0.05). No difference was detected for blood viscosity, RBC surface proteins, RBC adhesion, and RBC disaggregation threshold between the two conditions. During VOC, the percentage of ISCs was inversely correlated with deformability (p < 0.002 and p < 0.006 at 3 and 30 Pa, respectively), but positively correlated with RBC disaggregation threshold (p < 0.002) and with RBC adhesion to TrHBMECs (p < 0.008) (figure 1). At steady state, it was significantly correlated only with the disaggregation threshold (positive correlation, p < 0.03). Discussion: The most striking observation of this study is the positive correlation between ISCs (rigid cells) and RBC adhesion properties during overt VOC. This is in contrast with the general observation that the most deformable RBCs are those exhibiting the strongest adhesiveness and possibly involved in VOC initiation. Strengthened RBC aggregates may also disturb the blood flow into the microcirculation, hence participating to VOC progression and sustention. Drugs targeting RBC deformability (ISCs) and RBC aggregates might be helpful during established VOC in SCA. Disclosures No relevant conflicts of interest to declare.

Red Blood Cell Deformability Demonstrated with the Oxygenscan: Exploring the Association with Hydroxyurea Treatment, Co-Inherited α-Thalassemia, and Frequency of Pain in Children with Sickle Cell Anemia

Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 4834-4834
Author(s):  
Amina Nardo-Marino ◽  
Jesper Petersen ◽  
Andreas Glenthoej ◽  
John N. Brewin ◽  
Joergen Kurtzhals ◽  
...  
Keyword(s):  
Blood Cell ◽  
Sickle Cell ◽  
Sickle Cell Anemia ◽  
Red Blood Cell ◽  
Hemoglobin F ◽  
Positive Correlation ◽  
King's College ◽  
Hydroxyurea Treatment ◽  
Pain Frequency ◽  
Rbc Deformability

Background Sickle hemoglobin (hemoglobin S, HbS) is a structural variant of adult hemoglobin. HbS polymerizes when oxygen tensions are low, leading to red blood cell (RBC) deformation, so-called "sickling". In sickle cell anemia (SCA), loss of RBC deformability is considered to be a primary factor responsible for vaso-occlusion and hemolysis. Until recently no laboratory tests to measure RBC deformability in SCA have been readily available. Study Aims In this study we examine RBC deformability, measured with the oxygenscan module of the Laser Optical Rotational Red Cell Analyzer (Lorrca) ektacytometer, in children with SCA treated with or without hydroxyurea (HU). Furthermore, we investigate the relationship between RBC deformability and pain frequency, as well as genetic and laboratory measures known to be associated with disease severity in SCA. Methods We included children aged 0-16 years with a confirmed diagnosis of SCA (HbSS) from the pediatric sickle cell clinic at King's College Hospital in London. Children were excluded if they had received any blood transfusions within 3 months of study inclusion. Children on HU were only included if treatment had been initiated >3 months prior to recruitment and the dose was stable. Children and their parents or guardians reported frequency of pain as: daily, weekly, monthly, yearly, or never. Laboratory measurements, including total hemoglobin (hb), hemoglobin F (HbF), and reticulocyte percentage, were performed on the same day as a sample was taken for oxygenscan analysis. Data on co-inheritance of α-thalassemia was recorded if available. EDTA blood samples were kept at approximately 4°C and transported from King's College London to Copenhagen University Hospital (Herlev and Gentofte Hospital), where they were analyzed within 48 hours of sampling using the Lorrca oxygenscan (RR Mechatronics, the Netherlands). The oxygenscan measures RBC deformability expressed as an elongation index (EI) during deoxygenation and reoxygenation, with EImax expressing RBC deformability at normal oxygen concentrations, EImin expressing RBC deformability after deoxygenation, and the point of sickling (POS) expressing the point at which >5% decrease in EI is observed, representing the pO2 at which sickling begins. All statistical analyses were performed in Stata V16.0 (StataCorp. 2019, USA), using the two-sided t-test, one-way ANOVA, and Pearson's correlation when appropriate. Results We included 47 children aged 0-16 years (mean age 7.9 years) in the study, 24 (51%) receiving HU. Children in the HU group presented with significantly higher HbF percentage compared to the non-HU group (15.6% and 10.9%, p=0.03). Children receiving HU had higher EImax and EImin, and lower POS values, compared to children in the non-HU group, although results were not significant (Table 1). There was a positive correlation between HbF and EImax (r= 0.57, p=0.0001) and HbF and EImin (r= 0.56, p=0.0001), and a negative correlation between HbF and POS (r=-0.37, p=0.01), as well as a positive correlation between total hb and EImax (r=0.35, p=0.02). There was no significant correlation between any oxygenscan parameters and reticulocyte percentage. Data on α-thalassemia was available for 23 children. EImax and EImin values were higher in heterozygous children compared to children without co-inherited α-thalassemia, and POS values were lower, but results were not significant (Table 2). We found no significant association between any oxygenscan parameters and pain frequency (Table 3). Conclusion In this study we identified a strong correlation between all oxygenscan parameters and HbF percentage, as has been reported previously. We found higher EImax and EImin and lower POS values in children receiving HU treatment and children with co-inherited heterozygous α-thalassemia, suggesting increased RBC deformability in these children. These results were not significant, however, which may in part be due to lack of power in the study. Also, it is possible that children in the HU group would have presented with lower EImax and EImin and higher POS values prior to HU initiation, with treatment response leading to results similar to those found in the non-HU group. Finally, our results suggest that there is no association between oxygenscan parameters and self-reported frequency of pain in children with SCA. Disclosures No relevant conflicts of interest to declare.

scholarly journals Effects of Genotypes and Treatment on Oxygenscan Parameters in Sickle Cell Disease

Cells ◽  
2021 ◽  
Vol 10 (4) ◽  
pp. 811
Author(s):  
Camille Boisson ◽  
Minke A. E. Rab ◽  
Elie Nader ◽  
Céline Renoux ◽  
Celeste Kanne ◽  
...  
Keyword(s):  
Steady State ◽  
Sickle Cell Disease ◽  
Blood Cell ◽  
Sickle Cell ◽  
Red Blood Cell ◽  
Cell Disease ◽  
Oxygen Gradient ◽  
Acute Complication ◽  
Adults And Children ◽  
The Difference

(1) Background: The aim of the present study was to compare oxygen gradient ektacytometry parameters between sickle cell patients of different genotypes (SS, SC, and S/β+) or under different treatments (hydroxyurea or chronic red blood cell exchange). (2) Methods: Oxygen gradient ektacytometry was performed in 167 adults and children at steady state. In addition, five SS patients had oxygenscan measurements at steady state and during an acute complication requiring hospitalization. (3) Results: Red blood cell (RBC) deformability upon deoxygenation (EImin) and in normoxia (EImax) was increased, and the susceptibility of RBC to sickle upon deoxygenation was decreased in SC patients when compared to untreated SS patients older than 5 years old. SS patients under chronic red blood cell exchange had higher EImin and EImax and lower susceptibility of RBC to sickle upon deoxygenation compared to untreated SS patients, SS patients younger than 5 years old, and hydroxyurea-treated SS and SC patients. The susceptibility of RBC to sickle upon deoxygenation was increased in the five SS patients during acute complication compared to steady state, although the difference between steady state and acute complication was variable from one patient to another. (4) Conclusions: The present study demonstrates that oxygen gradient ektacytometry parameters are affected by sickle cell disease (SCD) genotype and treatment.

A physiometer for simultaneous measurement of whole blood viscosity and its determinants: hematocrit and red blood cell deformability

The Analyst ◽  
2019 ◽  
Vol 144 (9) ◽  
pp. 3144-3157 ◽  
Author(s):  
Byung Jun Kim ◽  
Ye Sung Lee ◽  
Alexander Zhbanov ◽  
Sung Yang
Keyword(s):  
Blood Cell ◽  
Red Blood Cell ◽  
Blood Viscosity ◽  
Simultaneous Measurement ◽  
Whole Blood ◽  
Cell Deformability ◽  
Whole Blood Viscosity ◽  
Red Blood Cell Deformability ◽  
Rbc Deformability

In this study, a microfluidic-based physiometer capable of measuring the whole blood viscosity, hematocrit, and red blood cell (RBC) deformability on a chip is introduced.

scholarly journals Does Higher Red Blood Cell (RBC) Lactate Transporter Activity Explain Impaired RBC Deformability in Sickle Cell Trait?

2005 ◽  
Vol 55 (6) ◽  
pp. 385-387 ◽  
Author(s):  
Philippe Connes ◽  
Fagnété Sara ◽  
Marie-Dominique Hardy-Dessources ◽  
Maryse Etienne-Julan ◽  
Olivier Hue
Keyword(s):  
Blood Cell ◽  
Sickle Cell ◽  
Red Blood Cell ◽  
Sickle Cell Trait ◽  
Lactate Transporter ◽  
Rbc Deformability

scholarly journals Whole blood viscosity and red blood cell adhesion: Potential biomarkers for targeted and curative therapies in sickle cell disease

2020 ◽  
Vol 95 (11) ◽  
pp. 1246-1256 ◽  
Author(s):  
Erdem Kucukal ◽  
Yuncheng Man ◽  
Ailis Hill ◽  
Shichen Liu ◽  
Allison Bode ◽  
...  
Keyword(s):  
Cell Adhesion ◽  
Sickle Cell Disease ◽  
Blood Cell ◽  
Sickle Cell ◽  
Red Blood Cell ◽  
Blood Viscosity ◽  
Whole Blood ◽  
Cell Disease ◽  
Whole Blood Viscosity ◽  
Potential Biomarkers

Effects of hydration and dehydration on blood rheology in sickle cell trait carriers during exercise

2010 ◽  
Vol 299 (3) ◽  
pp. H908-H914 ◽  
Author(s):  
Julien Tripette ◽  
Gylna Loko ◽  
Abdoulaye Samb ◽  
Bertin Doubi Gogh ◽  
Estelle Sewade ◽  
...  
Keyword(s):  
Body Weight ◽  
Blood Cell ◽  
Sickle Cell ◽  
Red Blood Cell ◽  
Blood Viscosity ◽  
Sickle Cell Trait ◽  
Blood Rheology ◽  
Plasma Viscosity ◽  
Adequate Hydration ◽  
Cont Group

This study compared the hemorheological responses of a group of sickle cell trait (SCT) carriers with those of a control (Cont) group in response to 40 min of submaximal exercise (exercise intensity, 55% aerobic peak power) performed in two conditions: one with water offered ad libitum, i.e., the hydration (Hyd) condition, and one without water, i.e., the dehydration (Dehyd) condition. Blood and plasma viscosities, as well as red blood cell rigidity, were determined at rest, at the end of exercise, and at 2 h recovery with a cone plate viscometer at high shear rate and 37°C. The SCT and Cont groups lost 1 ± 0.7 and 1.6 ± 0.6 kg of body weight, respectively, in the Dehyd condition, indicating a significant effect of water deprivation compared with the Hyd condition, in which body weight remained unchanged. Plasma viscosity increased with exercise and returned to baseline during recovery independently of the group and condition. As previously demonstrated, resting blood viscosity was greater in the SCT carriers than in the Cont group. Blood viscosity increased by the end of exercise and returned to baseline at 2 h recovery in the Cont group in both conditions. The blood viscosity of SCT carriers did not change in response to exercise in the Dehyd condition and remained elevated at 2 h recovery. This extended hyperviscosity, in association with other biological changes induced by exercise, could be considered as a risk factor for exercise-related events in SCT carriers, similar to vasoocclusive crises, notably during the recovery. In contrast, the Hyd condition normalized the hyperviscosity and red blood cell rigidity of the SCT carriers, with blood viscosity values reaching the same lower values as those found in the Cont group during the recovery. Adequate hydration of SCT carriers should be strongly promoted to reduce the clinical risk associated with potential hyperviscosity complications.

scholarly journals Red blood cell changes during the evolution of the sickle cell painful crisis

Blood ◽  
1992 ◽  
Vol 79 (8) ◽  
pp. 2154-2163 ◽  
Author(s):  
SK Ballas ◽  
ED Smith
Keyword(s):  
Blood Cell ◽  
Sickle Cell ◽  
Red Blood Cell ◽  
Reticulocyte Count ◽  
Hemoglobin Level ◽  
Second Phase ◽  
Osmotic Gradient ◽  
Cell Changes ◽  
Painful Crisis ◽  
Rbc Deformability

Abstract A longitudinal study of the red blood cell (RBC) deformability, percent of dense erythrocytes, and hematologic parameters has been conducted during 117 painful crises affecting 36 patients with sickle cell anemia between January, 1985 and December, 1990. RBC deformability was determined by osmotic gradient ektacytometry and the percentage of dense cells was quantitated by centrifugation on a discontinuous Stractan density gradient. The data indicate that the painful crisis is a process that follows a bimodal form of evolution. The first phase of the painful crisis is characterized by increase in the severity of pain, increase in the number of dense cells, and a decrease in RBC deformability. In some patients the changes in dense cells and RBC deformability are evident 1 to 3 days before the onset of pain. In addition, the hemoglobin level decreases and the reticulocyte count increases during this initial phase. The second phase of the crisis is characterized by reduction in pain intensity, decrease in the number of dense cells, and increase in RBC deformability to values higher than those seen in the steady state. Moreover, the improvement in RBC deformability and the decrease in the number of dense cells at the end of a crisis seem to constitute new risk factors that may incite a recurrence of the crisis within 1 month in about 50% of painful episodes. The pathophysiologic events responsible for this bimodal behavior of RBCs during painful episodes may represent the appearance of factors that induce (1) preferential trapping of deformable cells in the microcirculation during the first phase of the crisis, followed by a decrease of dense cells and the appearance of new deformable RBCs released from the bone marrow during the second phase of the crisis; or (2) variable sickling of all circulating RBCs during the first phase followed by disappearance of dense RBCs and their replenishment by deformable cells during the second phase.

scholarly journals Effects of Poloxamer 188 on Red Blood Cells Membrane Properties in Sickle Cell Disease

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 2174-2174
Author(s):  
Barbara Sandor ◽  
Mickael Marin ◽  
Claudine Lapoumeroulie ◽  
Miklos Rabai ◽  
Sophie Lefevre ◽  
...  
Keyword(s):  
Sickle Cell ◽  
Blood Viscosity ◽  
Blood Cells ◽  
Phase Iii ◽  
Adherent Cells ◽  
Escape Route ◽  
Rbc Aggregation ◽  
The Mean ◽  
Paired T Test ◽  
Rbc Deformability

Abstract Introduction: Sickle cell anemia (SCA) is a severe monogenic hereditary disorder characterized by chronic hemolytic anemia and the occurrence of frequent painful vaso-occlusive crises (VOC). SCA classical physiological scheme involves hemoglobin S polymerization under hypoxic conditions, which triggers red blood cells (RBCs) sickling. Recent studies demonstrated that the degree of hemorheological alterations, such as blood hyper-viscosity, determines the risk for VOC. Moreover, sickle RBCs abnormally adhere to the vascular endothelium, triggering microvascular occlusions. Despite extensive research very few drugs are available to efficiently treat VOCs or VOC-like events. A first clinical trial was performed to test the efficacy of poloxamer 188 (P188) in a large sickle cell cohort of adults and children (Orringer et al., 2001). This study demonstrated a significant reduction of pain duration in the children treated with P188. Recently, a new phase III multi-center trial has been started to test the efficacy of this drug during acute VOC in children (Humphries et al., 2015). We conducted in vitro experiments using the commercial formulation named Kolliphor P188 (Sigma-Aldrich) to test the effects of this drug on RBCs biophysical properties of SCA patients. Methods: To measure deformability and mechanical properties of RBCs, we used ektacytometry and microfluidic device mimicking the diameters of the micro vessels. RBCs adhesion assays were performed on HMEC-1 (Human Microvascular Endothelial Cell line) using dynamic flow adhesion platform. RBCs from healthy (AA) and SCA individuals were used for the different experiments. Results: While P188 did not significantly affect blood viscosity in AA, P188 treatment decreased blood viscosity at the lowest shear rates in SCA (Fig 1A). When measured in plasma, RBC aggregation decreased with P188 in SCA patients but not in AA (Fig 1B). RBC deformability assessed by both ektacytometry (not shown) and microfluidic device (Fig 2) was not affected by P188. This is in agreement with the mode of action of P188 suggesting that it binds to hydrophobic surfaces and lowers surface tension without any changes in the organization of the cytoskeleton. We examined the effect of P188 treatment on SCA-RBCs adhesion to the endothelial HMEC-1 cell line. We observed a mean adhesion of 40 cells/ mm2 for the untreated SCA-RBCs versus 20 cells/mm2 in the case of P188 treated RBCs, i.e. a 50% decrease upon P188 treatment (Fig 3). As for RBC aggregation, our findings suggest that the binding of P188 to SCA-RBCs membranes prevent the interaction with endothelial cells. This is of particular importance in the context of SCA since increased RBC adhesiveness has been demonstrated to trigger VOC. Conclusion: In parallel of the phase III clinical trial studying the profit of P188 for sickle cell patients during VOCs, our results bring clarifications regarding its mode of action on RBCs. We show that P188 directly reduces blood viscosity, RBC aggregation and adhesiveness to endothelial cells, making this drug as a potential beneficial therapy in SCA. References: Orringer, E.P., et al; (2001). JAMA, 286, 2099-2106. Humphries, J.D., et al; (2015). Trends Cell Biol, 25, 388-397. Figure 1. P188 treatment decreases blood viscosity (A) and RBC aggregation (B) in SS patients but not in AA controls. Figure 1. P188 treatment decreases blood viscosity (A) and RBC aggregation (B) in SS patients but not in AA controls. Figure 2. P188 treatment does not change SCA-RBC deformability. (A) Design of the microfluidic chip containing eight filtering units organized in parallel. Each filtering unit has a height of 5 µm and pillars are organized to allow an escape route of 20 µm around the unit to avoid occlusion. The surrounding pillars line has 5 µm slits. (B) Retention percentage of untreated and P188-treated SCA-RBC in 5 µm slits. Histograms represent mean of 5 µm slits from the 8 filtering units in one chip expressed in percent of total trapped RBCs for three patients. Figure 2. P188 treatment does not change SCA-RBC deformability. (A) Design of the microfluidic chip containing eight filtering units organized in parallel. Each filtering unit has a height of 5 µm and pillars are organized to allow an escape route of 20 µm around the unit to avoid occlusion. The surrounding pillars line has 5 µm slits. (B) Retention percentage of untreated and P188-treated SCA-RBC in 5 µm slits. Histograms represent mean of 5 µm slits from the 8 filtering units in one chip expressed in percent of total trapped RBCs for three patients. Figure 3. Graph representing adherent cells per mm2 at a flow rate of 1 dyne/mm2. The mean of the 5 patients is expressed as the average number of adherent cells/mm2 ± SD. Paired t test, P < 0.05. Figure 3. Graph representing adherent cells per mm2 at a flow rate of 1 dyne/mm2. The mean of the 5 patients is expressed as the average number of adherent cells/mm2 ± SD. Paired t test, P < 0.05. Disclosures No relevant conflicts of interest to declare.

scholarly journals THE RHEOLOGICAL PROPERTIES OF BLOOD IN THE MOST ACUTE STAGE OF ISCHEMIC STROKE AND THEIR RELATION TO THE SEVERITY OF NEUROLOGICAL IMPAIRMENT

2013 ◽  
Vol 12 (5) ◽  
pp. 5-12
Author(s):  
M. N. Azhermacheva ◽  
D. M. Plotnikov ◽  
O. I. Aliev ◽  
V. M. Alifirova ◽  
M. B. Plotnikov ◽  
...  
Keyword(s):  
Ischemic Stroke ◽  
Blood Cell ◽  
Red Blood Cell ◽  
Blood Viscosity ◽  
Cell Aggregation ◽  
Plasma Viscosity ◽  
Acute Stage ◽  
Rheological Parameters ◽  
Red Blood Cell Aggregation ◽  
Blood Cell Aggregation

The study evaluated the rheological parameters of blood: blood viscosity, plasma viscosity, hematocrit, red blood cell aggregation and deformability. The severity of the patients was assessed by clinical scales:Glasgowcoma scale, the scale NIHSS, Barthel index. The study found that in the acute phase of ischemic stroke increased blood viscosity by increasing red blood cell aggregation and reduced erythrocyte deformability. The increase in the viscosity of the blood in acute ischemic stroke is accompanied by increased severity of neurological disorders.

Capacity for red blood cell aggregation is higher in athletic mammalian species than in sedentary species

1994 ◽  
Vol 77 (4) ◽  
pp. 1790-1794 ◽  
Author(s):  
A. S. Popel ◽  
P. C. Johnson ◽  
M. V. Kameneva ◽  
M. A. Wild
Keyword(s):  
Shear Rate ◽  
Blood Cell ◽  
Aerobic Capacity ◽  
Sedimentation Rate ◽  
Red Blood Cell ◽  
Rheological Parameters ◽  
Specific Rate ◽  
Sheep Blood ◽  
Pronghorn Antelope ◽  
Rbc Aggregation

The purpose of this study was to show that two rheological parameters, red blood cell (RBC) sedimentation rate and apparent blood viscosity at low shear rate, characterizing the degree of RBC aggregation, correlate significantly with the maximal mass-specific rate of oxygen consumption or aerobic capacity (VO2max). Comparisons were made within two groups of similarly sized athletic and sedentary species: group 1, pronghorn antelope, dog, goat, and sheep; and group 2, horse and cow. The pronghorn antelope (Antilocapra americana) is one of the most athletic mammals, and we have obtained data on the rheological properties of blood from this species for the first time. The values of apparent viscosity at hematocrit = 40% and shear rate = 0.277 s-1 measured in a rotational viscometer were 59.5, 42.6, and 9.1 cP for antelope, dog, and sheep blood, respectively, and 55.3 and 11.5 cP for horse and cow blood, respectively. The viscosity values for antelope, dog, and sheep blood can be correlated with aerobic capacity: ln viscosity = 4.48–106.3 VO2(-1)max (r2 = 0.998; P < 0.05). The values of RBC sedimentation rate at hematocrit = 40% were 12.8, 7.0, and 0 mm/h for antelope, dog, and sheep blood, respectively, and 45.3 and 0.1 mm/h for horse and cow blood, respectively. Therefore, the data showed that the athletic species exhibit a consistently higher degree of RBC aggregation than do the corresponding nonathletic species.

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