M.C. Iazbik

Clinical pathology of Greyhounds and other sighthounds

Owing to the development of Greyhounds as racing sighthounds, these dogs have acquired unique physiologic adaptations that distinguish them from other breeds. Reference intervals for many analytes in retired racing Greyhounds (RRGs) differ from those of other breeds; most of the hematologic differences have also been described in other sighthounds. In this review, we provide a survey of the literature on clinical pathology of Greyhounds and other sighthounds and results of laboratory testing, including analysis of CBCs, biochemical profiles, coagulation tests, and blood gases, in RRGs at The Ohio State University. Major clinicopathologic differences in this breed include higher RBC mass, creatinine concentration, glomerular filtration rate, activities of hepatic enzymes, and concentration of cardiac troponin, as well as lower WBC, neutrophil, and platelet counts, thromboelastographic values, and concentrations of serum haptoglobin, total globulins, and T4.

Serum Cardiac Troponin I Concentration in Retired Racing Greyhounds

BACKGROUND Cardiac troponin I (cTnI) is a polypeptide found specifically in cardiac muscle tissue that has been used as a diagnostic and prognostic indicator of cardiomyopathy. Increases in cTnI are associated with myocardial pathologic processes. However, high serum cTnI concentrations have been observed in normal Greyhounds. HYPOTHESIS We hypothesized that Greyhounds have cTnI concentrations higher than non-Greyhound dogs, and that a separate reference range should be established for Greyhounds. ANIMALS Blood samples were collected from the jugular vein from a group of 20 healthy Greyhound blood donors. METHODS Analysis of serum cTnI was performed with an immunoassay system with a detection level of 0.01 ng/mL, as described previously. The Greyhound values were compared with 2 groups of Boxers with and without arrhythmogenic right ventricular cardiomyopathy (ARVC), and to a group of non-Boxer control dogs from a previous study. RESULTS The mean cTnI concentration in Greyhounds was significantly higher (P < .0001) than that in non-Greyhound control dogs, although not significantly different from normal Boxers (P= .50), or Boxers with ARVC (P= .58). Greyhound serum cTnI concentrations were in the range found in Boxers with ARVC. The proposed reference range for cTnI in Greyhounds is 0.05-0.16 ng/mL. CONCLUSIONS AND CLINICAL IMPORTANCE Greyhounds have a reference range for serum cTnI concentrations that differs from that of other previously published reference ranges for dogs of other breeds. Until a broader database and more precise reference range can be established, caution should be exercised in interpreting serum cTnI concentrations in Greyhounds with suspected cardiac disease.

Blood gas analysis and cooximetry in retired racing Greyhounds

OBJECTIVE The purposes of this study were to evaluate the oxygen affinity of hemoglobin (Hb) in healthy retired racing Greyhounds via cooximetry, and to establish reference intervals for blood gases and cooximetry in this breed. DESIGN Prospective clinical study. SETTING University Teaching Hospital. ANIMALS Fifty-seven Greyhounds and 30 non-Greyhound dogs. INTERVENTIONS Venous blood samples were collected from the jugular vein and placed into heparinized tubes. The samples were analyzed within 30 minutes of collection using a blood gas analyzer equipped with a cooximeter. MEASUREMENTS AND MAIN RESULTS Greyhounds had significantly higher pH, PO(2) , oxygen saturation, oxyhemoglobin, total Hb, oxygen content, and oxygen capacity and significantly lower deoxyhemoglobin and P(50) when compared with non-Greyhound dogs. CONCLUSION These findings support the fact that this breed is able to carry a higher concentration of total oxygen in the blood. As reported previously, this breed also has lower P(50) and, therefore, high oxygen affinity. In light of recent findings suggesting that in certain tissues a high affinity for oxygen is beneficial, this adaptation may be of benefit during strenuous exercise.

Plasma Vasoprotective Eicosanoid Concentrations in Healthy Greyhounds and Non-Greyhound Dogs

Background Hypertension and albuminuria often coexist in Greyhounds, suggesting generalized vascular dysfunction that could contribute to the development of a variety of diseases in this breed. Eicosanoid metabolites of arachidonic acid (AA) mediate endothelial function, vascular reactivity, and proteinuria in humans and in rodent models. Hypothesis The eicosanoid profile of Greyhounds is shifted toward metabolites that promote vascular dysfunction, hypertension, and proteinuria. Animals Healthy Greyhounds (n = 20) and non‐Greyhound (n = 20) dogs that were consecutively enrolled in a blood donor program. Methods Prospective study. Plasma eicosanoid metabolites were assayed by liquid chromatography/electrospray ionization mass spectrometry (LC/ESI/MS) and compared to systolic blood pressure (SP) measurements and urine albumin concentration. Results Isomers of hydroxyeicosatetraenoic acid (HETE) were higher in Greyhounds than non‐Greyhounds (median, range in pmol/mL: 5(S)HETE 19.82, 8.55–32.95 versus 13.54, 4.33–26.27, P = .033; 8(S)HETE 9.39, 3.28–19.84 versus 5.80, 2.25–17.66, P = .002; 9(S)HETE 9.46, 2.43–13.79 versus 5.82, 1.50–17.16, P = .026; 12(S)HETE 10.17, 3.81–40.06 versus 7.24, 2.9–16.16, P = .022). Dihydroxyeicosatrienoic acid (DHET) isomers also were higher in Greyhounds compared to non‐Greyhounds (mean ± SD in pmol/mL: 8,9DHET 5.78 ± 2.13 versus 4.03 ± 1.36, P = .004; 11,12DHET 11.98 ± 2.86 versus 8.90 ± 3.48, P = .004; 14,15DHET 7.23 ± 2.19 versus 5.76 ± 1.87, P = .028). Albuminuria correlated with total DHET (rs = 0.46, P = .003). SP was positively correlated with 11,12EET (rs = 0.42, P = .006) and 20(S)HETE (rs = 0.38, P = .017). SP and 8,9EET were inversely correlated (rs = −0.49, P = .001). Conclusions and Clinical Importance Plasma eicosanoid profile in Greyhounds was consistent with activation of metabolic pathways known to promote vascular dysfunction and might contribute to higher blood pressures and albuminuria. Inhibition of these eicosanoid pathways should be evaluated as therapeutic targets in Greyhounds.

Markers of iron metabolism in retired racing Greyhounds with and without osteosarcoma

BACKGROUND Greyhounds have well-described clinicopathologic idiosyncrasies, including a high prevalence of osteosarcoma (OSA). Hematocrit, HGB, and HGB oxygen affinity are higher than in other dogs, while haptoglobin concentration is lower, so we hypothesized that Greyhounds have a different iron metabolism. To our knowledge, there are no reports on serum iron profiles in Greyhounds. OBJECTIVES To elucidate iron metabolism in Greyhounds, we wanted to compare serum iron concentration, total iron-binding capacity (TIBC), and percent transferrin saturation (%SAT) in healthy retired racing Greyhounds (RRGs) with OSA (RRGs - OSA), and also with non-Greyhounds (NGs), without and with OSA (NGs - OSA). METHODS Serum iron concentration and unsaturated iron-binding capacity (UIBC) were measured by standard methods, and TIBC and %SAT were calculated in RRGs (n = 25), RRGs - OSA (n = 28), NGs (n = 30), and NGs - OSA (n = 32). RESULTS TIBC was lower in RRGs than in NGs (P < .0001), and in RRGs - OSA than in NGs - OSA (P < .0001). NGs - OSA had lower TIBC than healthy NGs (P = .003). Percent SAT was higher in RRGs than in NGs (P < .0001) and in RRGs - OSA (P = .008), and %SAT was also lower in NGs than in NGs - OSA (P = .004). Percent SAT was also higher in RRGs - OSA than in NGs - OSA (P = .001). Both RRGs - OSA (P = .02) and NGs - OSA (P < .0001) had lower serum iron concentrations than their healthy counterparts. CONCLUSION Lower TIBC and higher %SAT may constitute another Greyhound idiosyncrasy compared with other dogs. In this study, all dogs with OSA had higher serum iron concentrations and %SAT than healthy dogs.

Effects of racing on reticulocyte concentrations in Greyhounds

BACKGROUND Greyhounds have several hematologic variables that are outside of the respective reference intervals of other dog breeds. In addition, increases in HCT, total protein and HGB concentration, and RBC and WBC counts occur immediately after exercise; these values return to resting values within a few hour after racing. OBJECTIVE This study evaluated the effects of exercise on the concentration of reticulocytes in circulating blood in racing Greyhounds. We hypothesized that reticulocyte numbers are significantly increased immediately after a race, and return to baseline within one to 2 h postrace. METHODS Fifty actively racing Greyhounds at the Wheeling Island Racetrack and Casino were included in the study. Samples were collected by jugular venipuncture one day prior to racing at the kennel (resting), immediately after racing, and one to 2 h after the race (recovery). Reticulocyte counts were determined with an IDEXX ProCyte Dx Hematology Analyzer (IDEXX Laboratories, Inc., Westbrook, ME, USA). Due to a nonparametric distribution, the results were statistically compared using the Friedman test. RESULTS Reticulocyte concentrations were significantly different among the 3 sample collection times (P < .0001). There was a significant increase in reticulocyte concentration immediately after racing (P < .001); one to 2 h after racing, the reticulocyte numbers decreased significantly (P < .001) to counts comparable to resting samples. CONCLUSION The increase in reticulocyte concentration is probably related to splenic contraction secondary to the release of catecholamines, although premature bone marrow release could also account for these changes. Thus, it is important to consider a Greyhounds activity and degree of excitement when interpreting selected hematologic data in a clinical setting.

The Renin‐Angiotensin‐Aldosterone System in Greyhounds and Non‐Greyhound Dogs

Background The renin‐angiotensin‐aldosterone system (RAAS) regulates blood pressure, electrolyte homeostasis, and renal function. Blood pressure, serum sodium concentrations, and urinary albumin excretion are higher in Greyhounds than other purebred and mixed‐breed dogs. Hypothesis Alterations in the RAAS in Greyhounds are associated with hemodynamic and clinicopathologic differences observed in the breed. Animals Clinically healthy Greyhound and non‐Greyhound dogs consecutively enrolled as blood donors (n = 20/group). Methods Prospective study. Standard chemical analysis was performed on serum and urine. Serum angiotensin‐converting enzyme (ACE) activity was determined by fluorometric assay. All other RAAS hormones were determined by radioimmunoassay. Symmetric dimethylarginine (SDMA) was measured by immunoassay. Measurements were compared to blood pressure and urine albumin concentration. Data are presented as mean ± SD or median, range. Results Serum creatinine (1.5 ± 0.2 vs 1.0 ± 0.1 mg/dL, P < .001), sodium (149, 147–152 vs 148, 146–150 mEq/L, P = .017), and SDMA (16.1 ± 2.9 vs 12.2 ± 1.8 μg/dL, P < .001) were significantly higher in Greyhounds versus non‐Greyhounds, respectively. Plasma renin activity (0.69, 0.10–1.93 vs 0.65, 0.27–2.93 ng/mL/h, P = .60) and ACE activity (4.5, 2.1–8.5 vs 4.6, 2.1–11.4 activity/mL; P = .77) were similar between groups and did not correlate with higher systolic pressures and albuminuria in Greyhounds. Plasma aldosterone concentration was significantly lower in Greyhounds versus non‐Greyhounds (11, 11–52 vs 15, 11–56 pg/mL, respectively, P = .002). Conclusions and clinical importance Basal RAAS activation did not differ between healthy Greyhounds and non‐Greyhounds. Lower aldosterone concentration in Greyhounds is an appropriate physiologic response to higher serum sodium concentration and blood pressure, suggesting that angiotensin II effects in the renal tubule predominate over those of aldosterone.

Iron Status in Blood Donor Dogs

Background Despite the popularity of canine blood donor (BD) programs, there is scarce scientific information regarding iron status in this canine population of dogs. Objective To assess iron status in dogs used in a blood donor program. Animals A total of 130 healthy dogs (75 BD, 55 controls [C]) were included. A subset of dogs (n = 12) were used to evaluate the effects of repetitive donations by having a second and more recent sample analyzed. Methods Serum iron concentration (SI), unsaturated iron‐binding capacity (UIBC), total iron‐binding capacity (TIBC), and percentage transferrin saturation (%SAT) were obtained. Values were compared using a 2‐way ANOVA (factors: BD status, breed). For the subset of BD, the first sample (less frequent donors ‐LD‐, after a mean of 3.8 donations) was compared to a second sample (experienced donors ‐ED‐, mean 13.6 donations) using a paired t‐test. Results SI (183.7 ± 55.3 μg/dL) and %SAT (55.7 ± 17.4%) were higher and UIBC (152.6 ± 73.3 μg/dL) was lower in BD dogs than in C (153.9 ± 51.7 μg/dL, 43.8 ± 17.8%, and 224.1 ± 120.6 μg/dL, respectively). Also, UIBC and TIBC were lower, and %SAT higher in Greyhounds when compared with non‐Greyhounds. ED had decreased %SAT and increased UIBC and TIBC when compared with LD. Conclusions and Clinical Importance Our canine BD population did not have iron deficiency and had higher SI concentration than C. However, ED (~14 consecutive blood donations every ~8 weeks) developed a mild iron deficiency, although values were still within canine reference intervals. Greyhounds have higher %SAT than non‐Greyhounds, which might be a breed‐specific peculiarity.

Effects of time of collection and sample processing on von Willebrand factor concentration in retired racing Greyhounds

BACKGROUND Concentrations of von Willebrand factor (vWF) are less than 30% in approximately 10% of Greyhounds. HYPOTHESIS That sample collection, processing, and storage can affect the concentration of vWF in plasma of Greyhounds. ANIMALS Nineteen healthy former racing Greyhounds. METHODS Prospective study: Blood samples were obtained from the jugular vein of dogs at 4 times during the day. Samples were divided and processed in each of 3 ways. The 1st tube was centrifuged immediately, the 2nd tube was kept in a household refrigerator, and the 3rd tube was kept at room temperature for 3 hours before centrifugation and processing. RESULTS There were no significant differences in the vWF concentration between different sample storage and processing (P = 5.31). There was no statistically significant diurnal variation in vWF concentration in the samples evaluated (P = .37). CONCLUSIONS AND CLINICAL IMPORTANCE Time of sample collection and short-term storage temperature do not influence the vWF concentration in retired racing Greyhounds.