C.G. Couto

Thromboelastographic Tracings in Retired Racing Greyhounds and in Non‐Greyhound Dogs

BACKGROUND Bleeding disorders in patients with normal coagulation test results are frequently reported in Greyhounds. The purpose of this study was to compare Greyhounds to non-Greyhounds by thromboelastography (TEG). HYPOTHESIS TEG parameters in Greyhounds are different from those in non-Greyhounds. ANIMALS Forty-three healthy dogs (28 Greyhounds and 15 non-Greyhounds) based on the results of physical examination, CBC, activated partial thromboplastin time, prothrombin time, fibrinogen, and platelet count. MATERIALS AND METHODS Recalcified citrated native TEGs were performed in both groups; data were compared using Students, Mann-Whitney, and Pearsons statistical tests. RESULTS In Greyhounds, mean +/- SD were as follows: R-time 4.3 +/- 1.7 minutes, K-time 3.8 +/- 1.4 minutes, angle (alpha) 50.0 +/- 8.0 degrees , maximum amplitude (MA) 47.6 +/- 5.6 mm, clot strength (G) 4,647 +/- 1,097 dyn/cm2, and percent lysis at 60 minutes (LY60) 2.8 +/- 5.0%. In the non-Greyhounds they were R-time 3.7 +/- 1.6 minutes, K-time 2.5 +/- 0.9 minutes, angle 59.8 +/- 7.0 degrees , MA 53.1 +/- 5.6 mm, G 5,811 +/- 1,256 dyn/cm2, and LY60 3.1 +/- 2.5%. All parameters were significantly different between the groups, except for R-time and LY60. CONCLUSION In Greyhounds, clotting kinetics are slower and clot strength are weaker than in non-Greyhounds, supporting the increased tendency to bleed observed after minor trauma or surgical procedures in the breed. The findings may also be attributed to blood viscosity or to the concentration of citrate in the sample (ie, Greyhounds have higher hematocrit and less plasma per unit volume).

Phase I Clinical Evaluation of Carboplatin in Tumor-Bearing Cats: A Veterinary Cooperative Oncology Group Study

BACKGROUND The dosage of carboplatin in cats has been reported anecdotally and experimentally in non-tumor-bearing cats, but the dosage for carboplatin treatment in tumor-bearing cats has yet to be defined in a prospective clinical trial. PURPOSE To determine the maximally tolerated dose (MTD) and dose-limiting toxicosis (DLT) of carboplatin in tumor-bearing cats. CATS: Fifty-nine cats with measurable solid tumors. METHODS The starting dose of carboplatin was 160 mg/m(2) of body surface area IV. Doses were increased by 20 mg/m(2) in cohorts of 3-14 cats until the MTD was reached. RESULTS The 59 cats entered into this multi-institutional phase I study received 1 or more doses of carboplatin at various dosages and were evaluated for toxicity, response to treatment, or both. The MTD was 240 mg/m(2) and neutropenia was the DLT. For the 1st cycle of treatment in 44 cats evaluated for neutropenia, 6 episodes of grade 3 or greater neutropenia occurred on days 7 (n=1), 14 (n=4), and 21 (n=1). There was no evidence of drug-induced nephrotoxicosis or pulmonary edema. Preliminary evidence of antitumor activity was observed in 7 of 59 (11.9%; 95% CI, 5.6-22.8%) cats evaluated for response to treatment. There was 1 complete response (cutaneous hemangiosarcoma) and 6 partial responses (4 injection site sarcomas, 1 oral squamous cell carcinoma, 1 lymphoma). Responses were of short duration (median, 42 days; range, 7-168 days). CONCLUSIONS AND CLINICAL IMPORTANCE The dose of carboplatin recommended to treat tumor-bearing cats is 240 mg/m(2) IV every 3-4 weeks.

Postoperative Bleeding in Retired Racing Greyhounds

BACKGROUND Some retired racing Greyhounds (RRG) that undergo surgery bleed excessively. HYPOTHESIS Greyhounds that bleed excessively will have one or more preoperative hemostatic abnormalities that can be used to predict the risk and severity of postoperative bleeding. ANIMALS Eighty-eight RRG undergoing ovariohysterectomy or castration. METHODS All dogs were evaluated preoperatively with a physical exam, CBC, platelet count, OSPT, APTT, platelet function with PFA-100(a); fibrinogen, d-dimer, plasminogen (Plmg), antiplasmin (AP), antithrombin (AT), and vWF concentration (vWF:Ag); vWF collagen binding assay (vWF:CBA), and Factor XIII assay. Assays were repeated in the dogs that bled, and in an age- and sex-matched control group of RRG. RESULTS Twenty-six percent of the dogs had bleeding 36-48 hours after surgery. AP (P <.0001) and AT concentration (P= .007) were significantly lower, and vWF:CBA (P= .0284) was higher preoperatively in the dogs with excessive hemorrhage. A lower platelet count (P= .001) and hematocrit (P= .002), shorter OSPT (P= .0002) and higher plasma fibrinogen (P <.0001), and AP (P= .001) concentration were detected at the time of bleeding compared with preoperative values in the dogs that bleed excessively. The same findings were observed postoperatively for the control group, except for the decrease in hematocrit. CONCLUSIONS AND CLINICAL IMPORTANCE The results indicate that this excessive postoperative bleeding is not attributable to a primary or secondary hemostatic defect, but could result from altered fibrinolysis.

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.

White‐Coat Effect on Systemic Blood Pressure in Retired Racing Greyhounds

BACKGROUND Greyhounds are known to have a higher systemic arterial blood pressure (BP) than non-Greyhound dogs. OBJECTIVES The purpose of this study was to determine whether the high systemic BP was because of the white-coat effect. ANIMALS Twenty-two healthy retired racing Greyhounds (RRG) enrolled in a blood donation program. MATERIALS/METHODS We prospectively measured systemic BP in 3 environments: in the hospital by the investigator (Hosp), in the home by the investigator (H/I), and in the home by the owner (H/O). Five serial measurements of systolic, diastolic, and mean arterial pressures (SAP, DAP, MAP) as well as heart rate (HR) were measured by an oscillometric method on the distal forelimb and distal hind limb in all 3 environments. RESULTS There was a significant difference for SAP, MAP, and HR between the Hosp and both H/I and H/O (P < .001); there were no significant differences for any of the parameters between the H/I and H/O environments. HR, but not SAP, MAP, or DAP (P < .05) decreased in RRG with multiple hospital visits for blood donation before this study. The hind limb SAP was significantly higher than the forelimb SAP (P < .05). CONCLUSIONS AND CLINICAL IMPORTANCE We conclude that the high SAP, MAP, and HR seen in the hospital setting are likely because of a white-coat effect. Furthermore, consideration should be given to defining the parameters of normal BP in RRG according to the environment in which they are obtained.

Prevalence of elevated alanine transaminase activity in dogs treated with CCNU (Lomustine).

The purpose of this study was to evaluate prevalence of serum alanine transaminase (ALT) elevation in dogs receiving lomustine (CCNU) and to analyse the pattern of occurrence and potential risk factors. Serum ALT activity in 109 dogs during single-agent CCNU chemotherapy was retrospectively analysed. The median initial dose, dose-intensity and cumulative dose of CCNU were 64 mg m(-2), 21 mg m(-2) week(-1) and 171 mg m(-2), respectively. The overall prevalence of major ALT elevation [> 5-fold upper reference limit (URL)] was 29% (32/109) and developed most commonly after one to three doses of CCNU. These ALT elevations occurred without preceding mild ALT elevation in 53% (17/32) of the cases. Three dogs (2.8%) developed clinical hepatopathy. For severe ALT elevation (>10-fold URL), age < or =5-year-old was associated with higher risk. The findings of this study showed that elevation of ALT is common during CCNU chemotherapy in dogs and severe elevation can develop on a sudden onset.

Arterial Blood Pressure, Proteinuria, and Renal Histopathology in Clinically Healthy Retired Racing Greyhounds

BACKGROUND Physiologic peculiarities of Greyhounds as compared to other dogs make interpretation of laboratory results in this breed challenging for veterinarians. Hypertension in retired racing Greyhounds (RRG) can contribute to microalbuminuria (MA), overt proteinuria, and renal histologic lesions. OBJECTIVES To evaluate clinicopathologic findings, hemodynamic status, and renal histology in a population of healthy RRG. ANIMALS RRG presented to Ohio State University College of Veterinary Medicine for inclusion in a spay and neuter program. METHODS Cross-sectional study. RRG were classified as normotensive (<160 mmHg) or hypertensive (>160 mmHg) based on blood pressure (BP) determinations using Doppler and oscillometric methods. Of the dogs evaluated, 62% (n = 29) were hypertensive and 38% (n = 18) were normotensive. Health status was evaluated using routine clinicopathologic tests (CBC, serum biochemistry, urinalysis) as well as evaluation of fractional excretion of electrolytes and MA determinations. Adequate renal biopsy specimens (n = 15) were evaluated using light, immunofluoresence, and electron microscopy. RESULTS All serum biochemistry results were normal in 45/49 dogs, but MA was more common in hypertensive (84% positive for MA) as compared with normotensive (18% positive for MA) RRG. Observed renal lesions were mild and renal biopsy scores were low in this sample of RRG. CONCLUSIONS Hypertension is common in RRG and might be breed-related. It is associated with MA, but observed renal lesions are mild. Whether or not hypertension and MA in RRG leads to progressive renal damage requires longitudinal study.

3-Phosphoinositide-dependent protein kinase-1/Akt signalling and inhibition in a canine prostate carcinoma cell line.

Deregulation of the 3-phosphoinositide-dependent protein kinase-1 (PDK-1)/Akt signalling pathway is associated with prostate cancer development and progression. Inhibition of PDK-1/Akt signalling can be achieved using structurally optimized celecoxib derivatives such as OSU-03012. In this study, we treated the novel canine prostate cancer cell line, Ace-1, with OSU-03012 or dimethyl sulphoxide in vitro. We found that Akt was constitutively phosphorylated in the canine prostate cancer cell line Ace-1 and that there was a dose-dependent decrease in cell viability, and Akt and glycogen synthase kinase-3beta phosphorylation, in response to OSU-03012 treatment. This was accompanied by a dose-dependent increase in apoptosis. These data suggest that Akt signalling pathway inhibition is a potential strategy for the treatment of dogs with prostate cancer and that canine prostate cancer is a relevant large animal model for evaluating Akt pathway inhibitors such as OSU-03012 for use in people.

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.

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.