Feasibility, safety, and tolerance of subcutaneous synthetic canine B-type natriuretic peptide (syncBNP) in healthy dogs and dogs with stage B1 mitral valve disease.

INTRODUCTION: An important aspect of heart failure is the progressive ineffectiveness of the salutary natriuretic peptide system and its secondary messenger, 3',5'-cyclic guanosine monophosphate (cGMP). In humans with acute heart failure, administration of exogenous natriuretic peptide is associated with improvement in clinical signs and reduction of cardiac filling pressures. This study aimed to determine the feasibility, tolerance, and safety of subcutaneous (SC) synthetic canine B-type natriuretic peptide (syncBNP) administration in dogs. ANIMALS: Six privately owned dogs. MATERIALS AND METHODS: Dogs were enrolled in a modified 3 + 3 phase I trial. Three dogs initially received doses of 2.5 and 5 µg/kg SC syncBNP followed by an additional three dogs dosed at 5 and 10 µg/kg. Hemodynamic monitoring was performed for 120 min after each injection. Blood and urine samples were collected at 45 and 120 min after injection of 5 µg/kg. Major adverse clinical events that would potentially halt testing were pre-defined. RESULTS: Four healthy dogs and two dogs with stage B1 mitral valve disease were recruited. Synthetic canine B-type natriuretic peptide was well tolerated at all doses. Synthetic canine B-type natriuretic peptide at 5 µg/kg significantly increased median plasma cGMP (baseline cGMP, 131.5 pmol/mL [range, 91.9-183.6 pmol/mL]; 45 min, 153.6 pmol/mL [140.3-214.3 pmol/mL]; 120 min, 192.7 pmol/mL [139.1-240.1 pmol/mL]; p=0.041). DISCUSSION AND CONCLUSIONS: We report for the first time administration of syncBNP in privately owned dogs. Administration of SC syncBNP was feasible, well tolerated, safe, and increased plasma cGMP concentration. Further studies using exogenous syncBNP for treatment of heart disease are warranted.

Immunohistochemistry of atrial and brain natriuretic peptides in control cats and cats with hypertrophic cardiomyopathy.

Atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) are cardiac hormones involved in electrolyte and fluid homeostasis. Our laboratory has investigated the use of ANP and BNP as diagnostic markers of cardiac disease in cats. We hypothesize that the cardiac distribution of ANP and BNP increases in cats with hypertrophic cardiomyopathy (HCM). Accordingly, we evaluated the immunohistochemical distribution of ANP and BNP in hearts of four cats with naturally occurring HCM relative to five healthy controls. Indirect immunoperoxidase was performed with polyclonal immunoglobulin G against feline ANP (1-28) and proBNP (43-56). In control cats, ANP and BNP immunoreactivity was restricted to the atria. Staining for both peptides was most intense adjacent to the endocardial surface. Auricles stained more diffusely than atria for both peptides. The interstitial capillaries and nerve fibers within the heart were positive only for BNP. Atrial immunoreactivity for ANP and BNP was more diffuse and had a less distinctly layered pattern in HCM than in control cats. Ventricular cardiomyocytes of HCM cats were negative for ANP but stained lightly and diffusely for BNP. The capillaries and nerve fibers remained positive for BNP. We conclude that in cats with HCM, the cardiac distribution of ANP and BNP is more diffuse in the atria and that novel expression of BNP in the ventricular cardiomyocytes occurs.

Characterization of sublethal microcystin-LR exposure in mice.

Microcystin-LR (MCLR) is a potent hepatotoxin produced by the cyanobacterium Microcystis aeruginosa. The histology of acute lethal toxicity has been well characterized, but histology is limited regarding sublethal exposure. Balb/C mice were given a single sublethal dose of MCLR (45 microg/kg) and euthanized at 2, 4, 12, and 24 hours after exposure. Centrilobular to midzonal hepatocellular hypertrophy with loss of cytosolic vacuolation consistent with glycogen depletion occurred at 2 hours. At 4 hours, central lobular hepatocytes exhibited eccentric areas of eosinophilic cytoplasmic condensation that were partially aggregated around the outer nuclear membrane. The areas were weakly positive for cytokeratin and somewhat resembled the Mallory bodies of alcoholic human hepatitis. Small numbers of apoptotic hepatocytes were seen at 24 hours. The toxin was detectable by immunohistochemistry (IHC) as early as 2 hours and was colocalized with the areas of hepatocellular hypertrophy. Intense nuclear staining occurred at 4 hours; this was no longer evident after 12 hours. Strong staining of apoptotic bodies occurred at 24 hours. Mice that received two daily doses had a marked increase in apoptotic hepatocytes in the centrilobular areas. Lesions at four and seven doses consisted of marked hepatocytomegaly and karyomegaly with parenchymal disarray and cytosolic vacuolation. IHC revealed diffuse staining throughout the liver parenchyma consistent with toxin accumulation. An anti-MCLR monoclonal antibody detected bands at the 40-kDa mark in nuclear extracts that were identified as protein phosphatases 1 and 2A by western blotting, consistent with a covalent interaction between MCLR and nuclear protein phosphatases.

Intrarenal effects of ecadotril during acute volume expansion in dogs with congestive heart failure.

Neutral endopeptidase 24.11 (NEP) inhibitors are known to have vascular, diuretic, and natriuretic effects that may be helpful in the treatment of congestive heart failure (CHF). Most NEP inhibitors may act principally through intrarenal mechanisms, which are not completely understood. The purpose of this study was to determine the principal renal effects of the NEP inhibitor ecadotril in dogs with progressive CHF induced by rapid ventricular pacing. Renal function was measured before, during, and after acute i.v. infusion of normal saline in a total of six dogs during normal cardiac function, early left ventricular dysfunction, and overt CHF. During overt CHF, each dog was treated with either ecadotril or placebo orally for 1 week. Parameters measured included glomerular filtration rate, renal blood flow, urine output, sodium clearance, sodium fractional excretion, and proximal and distal sodium reabsorption. Ecadotril treatment resulted in increased urine output, sodium clearance, and renal sodium excretion relative to placebo-treated controls. The principal intrarenal effect of ecadotril was decreased distal renal tubular sodium reabsorption. Both glomerular filtration rate and renal blood flow declined during overt CHF and were unaffected by ecadotril treatment. The results of this study are consistent with the principal action of ecadotril occurring by way of intrarenal events as opposed to changes in renal hemodynamics. The principal effect of ecadotril on distal tubular sodium reabsorption suggests that inhibition of NEP activity in the proximal renal tubules may allow increased binding of filtered atrial natriuretic peptide to natriuretic peptide receptor sites in the distal renal tubules and collecting ducts.

Decreased hepatic ALT synthesis is an outcome of subchronic microcystin-LR toxicity.

Alanine aminotransferase (ALT; EC 2.6.1.2) is important for the transamination of amino acids and is also an important serum marker of hepatic damage. However, we had previously shown that hepatic ALT activity decreases with subchronic exposure to the hepatotoxin, microcystin-LR (MCLR), a potent inhibitor of serine/threonine protein phosphatases types 1 and 2A. These previous findings suggest that one outcome of subchronic MCLR toxicosis is decreased ALT synthesis by hepatocytes. This could affect the diagnostic sensitivity of serum ALT activity and metabolic processes within the cell. This study was done to investigate the mechanism by which ALT activity decreases following prolonged MCLR exposure. Immunoblots were first performed on liver tissue from 12 Harlan-Sprague-Dawley rats that had been treated with 0, 16, 32, or 48 microg/kg of microcystin-LR per day by continuous intraperitoneal infusion for 28 days. These revealed a dose-dependent decrease in ALT protein concentrations that correlated directly with hepatic ALT activity (r = 0.8132; P = 0.0013). Sixteen additional rats, treated with the same doses of MCLR showed a dose-dependent decrease in hepatic ALT activity to approximately 19% of values in saline-treated controls. Northern blot analysis revealed a decrease in hepatic ALT mRNA that correlated directly to hepatic ALT activity (r = 0.7909; P = 0.0004). It was concluded that subchronic MCLR exposure causes decreased hepatic ALT protein and mRNA concentrations. These findings suggest that one sequela of MCLR toxicosis is decreased hepatic ALT synthesis.

Correlation of two nonradioactive immunoassays to a radioimmunoassay technique for thyroxine measurement in equine serum.

The purpose of this study was to compare 2 different nonradioactive assay methods with a conventional radioimmunoassay (RIA) measuring the concentration of serum thyroxine (T4) in horses. Serum was obtained from 85 adult standardbred horses. The T4 concentration of each sample was analyzed by RIA, chemiluminescent enzyme immunoassay (CEI), and homogeneous enzyme immunoassay (HEI). The correlation between the HEI method and RIA method was significantly greater (r = 0.89) than the correlation between the CEI and the reference method (r = 0.53). In addition, the precision of the HEI method was significantly greater than the CEI method; within-run percentage coefficients of variation were 4.5% and 15.9%, respectively, at mean T4 concentrations of 19-20 nmol/liter. On the basis of these findings, the HEI method was evaluated further. Both between-run precision and linearity were deemed adequate upon dilution by the HEI method. In addition, recovery of L-thyroxine added to equine serum was linear over 6 concentrations tested and averaged 79.6% with a manufacturer recommended data correction factor. An in-house correction factor was calculated by linear regression analysis of the RIA and HEI results from the original equine serum samples. Use of this correction factor improved the average recovery to 94.2% while maintaining excellent linearity (r2 = 0.9978). Although both nonradioactive methods of T4 analysis could likely substitute for the RIA reference method, the HEI method had the highest correlation and precision. The HEI technique also yielded adequately accurate results after correction of the data with an appropriate correction factor. Individually derived in-house correction factors may improve the accuracy of the HEI method to a greater extent than manufacturer suggested correction factors.

Results of hematologic analyses and prevalence of physiologic leukopenia in Belgian Tervuren.

OBJECTIVE: To determine reference ranges for results of hematologic analyses of healthy Belgian Tervuren, to compare results of hematologic analyses for healthy Belgian Tervuren with results for healthy dogs of other breeds, and to determine prevalence of physiologic leukopenia in Belgian Tervuren. DESIGN: Cohort study. ANIMALS: 180 healthy Belgian Tervuren and 63 healthy dogs of other breeds. PROCEDURE: Blood samples were analyzed by use of an automated device. Reference ranges were calculated for Belgian Tervuren by use of standard methods. RESULTS: Total WBC counts of Belgian Tervuren ranged from 2.61 to 16.90 x 10(3)/microl. Mean WBC count of Belgian Tervuren (mean +/- SEM, 7.04 +/- 0.16 x 10(3)/microl) was significantly lower than mean count for control dogs. Significantly more Belgian Tervuren (65/180; 36%) than control dogs (2/63; 3%) had WBC counts < 6.00 x 10(3)/microl. Percentage of Belgian Tervuren with WBC count < 6.00 x 103/microl was low for dogs < or = 2 years old, increased sharply for dogs between 2 and 4 years old, and was approximately 65% for dogs > 4 years old. Neutrophil, lymphocyte, and monocyte counts were significantly lower, and RBC count, hematocrit, and eosinophil fraction were significantly higher in Belgian Tervuren than in control dogs. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that physiologic leukopenia, resulting from low numbers of neutrophils, lymphocytes, and monocytes, may be a typical finding in a large percentage of healthy Belgian Tervuren and is not of clinical importance in otherwise healthy dogs. Healthy Belgian Tervuren may also have RBC counts and hematocrits higher than expected for healthy dogs.

Hepatic oxidative stress following prolonged sublethal microcystin LR exposure.

Microcystin LR (MCLR) is a naturally occurring protein phosphatase inhibitor and potent hepatotoxin produced by strains of Microcystis aeruginosa. Although its acute toxicity has been well characterized, little is known about its chronic effects. In this study, we sought to acquire evidence that oxidative stress may play a role in the pathogenesis of prolonged sublethal MCLR toxicity. Twelve rats (3 per group) weighing on average 185 g were exposed to 1 of 3 different concentrations of MCLR (16, 32, and 48 microg/kg/day) or to saline via intraperitoneal osmotic pumps for 28 days. Histologic evidence of dose-dependent hepatic inflammation was seen, including infiltration of centrilobular regions by lymphocytes, macrophages, and neutrophils, centrilobular fibrosis, apoptosis, and steatosis. Analysis of lipid peroxidation products revealed a dose-dependent increase in malondialdehyde concentrations with an approximate 4-fold increase in the livers of the high-dose rats over those of the saline-treated controls. Livers from MCLR-exposed rats were more sensitive than those of controls to the cytotoxic effects of the organic oxidizing agent tert-butyl hydroperoxide, based on an MTT (3-[dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium bromide) viability assay. These histopathologic and biochemical findings indicate that oxidative stress may play a significant role in the pathogenesis of chronic MCLR toxicosis.

Leukopenia in six healthy Belgian Tervuren.

A healthy 6.5-year-old sexually intact female Belgian Tervuren was found to be persistently leukopenic during preoperative evaluation for routine ovariohysterectomy. Abnormalities of the erythroid or myeloid series were not detected during bone marrow analysis. Blood samples for CBC were collected from 8 additional healthy Belgian Tervuren of both sexes and of various ages. Six of the 9 dogs were leukopenic, with WBC counts between 2.38 and 5.42 x 10(3) WBC/microl (mean +/- SD, 4.13 +/- 1.04 x 10(3) WBC/microl). Leukopenia was a persistent finding in the 3 dogs from which multiple blood samples were collected. All dogs were otherwise clinically normal. Leukopenia, as defined by a WBC count < 6.00 x 10(3) WBC/microl, may be a common finding in the Belgian Tervuren breed.

Solubilization of liver alkaline phosphatase isoenzyme during cholestasis in dogs.

OBJECTIVE: To determine the mechanism by which liver alkaline phosphatase (LALP) isoenzyme is converted from a membrane-bound enzyme to the soluble enzyme during cholestasis. SAMPLE POPULATION: Serum and tissues from 2 dogs. PROCEDURE: The LALP was purified by use of affinity chromatography in samples of serum from dogs with complete bile duct obstruction. Gas chromatography/mass spectrometry was used to detect myo-inositol residues that would be evident when serum LALP had been membrane-attached and released by phospholipase activity. Exclusion chromatography, gel electrophoresis, and octyl-sepharose phase separation of the serum isolate were used to confirm cleavage of the hydrophobic membrane anchor. Western immunoblot analysis was used to distinguish release by glycosylphosphatidylinositol phospholipase D (GPI-PLD) from that by glycosylphosphatidylinositol phospholipase C (GPI-PLC). Intact hepatocytes were incubated with canine serum GPI-PLD to test sensitivity of LALP to release by GPI-PLD. Hepatocyte membrane fragments were treated with serum GPI-PLD and mixtures of taurocholate and taurodeoxycholate to test effects of bile acids on LALP release. RESULTS: Amounts of myo-inositol per mole of serum LALP isolate were equal to amounts detected with LALP isolated from hepatic tissue. Evaluation of results of western immunoblot analysis and electrophoretic mobility suggested release by GPI-PLD rather than by GPI-PLC. Membrane-bound LALP was resistant to serum GPI-PLD activity in the absence of bile acids; however, incubation in the presence of bile acids caused release of LALP. CONCLUSIONS: Solubilization of LALP during cholestasis involves cleavage of its membrane anchor by endogenous GPI-PLD activity. Action of GPI-PLD is likely enhanced by increased concentrations of hepatic bile acids during cholestasis.

Prolonged sublethal exposure to the protein phosphatase inhibitor microcystin-LR results in multiple dose-dependent hepatotoxic effects.

The purpose of this study was to relate dose-dependent hepatotoxicity stemming from prolonged exposure to sublethal concentrations of the cyclic heptapeptide microcystin-LR (Mcyst) to hepatic Mcyst concentrations and protein phosphatase activity. Mcyst is a potent inhibitor of protein phosphatase types 1 and 2A (PP1 and PP2A). Twenty male Sprague-Dawley rats were infused continuously with 0, 3, 6, or 9 micrograms Mcyst/day for 28 days using intraperitoneal mini-osmotic pumps containing highly purified toxin or saline. At the end of 28 days, dose-dependent increases in several serum biochemical tests including sorbitol dehydrogenase, aspartate aminotransferase, gamma-glutamyl transferase, alkaline phosphatase, and bile acids had occurred. Serum albumin decreased in a dose-dependent fashion. Liver activity of both PP1 and PP2A decreased in a dose-dependent manner, but with a relatively greater effect on PP2A than PP1. Liver cytosol Mcyst concentrations, measured by direct competitive ELISA, also increased in a dose-dependent manner, although at a higher rate than would be predicted from the incremental increase in dose given. This disproportional increase is suggestive of the bioaccumulation of Mcyst with increasing dose. Histopathological abnormalities included hepatocellular apoptosis and cytosolic vacuolation of principally zone 3 hepatocytes. Immunohistochemical stains revealed Mcyst predominantly within pericanalicular regions of zone 3 hepatocytes. It was concluded that prolonged exposure to sublethal concentrations of Mcyst results in multiple dose-dependent hepatotoxic effects that correspond to decreased hepatic serine/threonine protein phosphatase activity and increasing cytosolic Mcyst concentrations. The disproportional increase of hepatic Mcyst concentrations observed may suggest the bioaccumulation of toxin and an increasing relative risk of hepatotoxicity with increasing dose.

CCK-8 infusion increases plasma LMW alkaline phosphatase coincident with enterohepatic circulation of bile acids.

Bile acids may facilitate the release of liver alkaline phosphatase (ALP) from its hydrophobic membrane anchor. The purpose of this study was to determine whether such a facilitatory role could be observed during the enterohepatic circulation of bile acids in dogs. Increased hepatic ALP activity was induced in four dogs by daily injections of 4 mg.kg-1.day-1 of prednisone for 10 days. Intravenous infusions of cholecystokinin octapeptide (CCK-8) were given before treatment and on treatment days 3, 5, 7, and 10 to induce gallbladder emptying and the enterohepatic circulation of bile acids. Blood samples were taken hourly for 4 h before and for 4 h after CCK-8 infusion. These showed that plasma ALP activity increased significantly only after CCK-8 infusion. Gel exclusion chromatography, polyacrylamide gel electrophoresis, and octyl Sepharose phase separation showed that the increased ALP activity was a hydrophilic, low-molecular-weight (LMW) isoform, which is consistent with phospholipase release. Histochemical staining of endogenous ALP activity showed increased ALP activity over sinusoidal surfaces of prednisone-treated dogs. There was also an increased serum-to-tissue ratio of ALP activity in the prednisone-treated dogs, suggestive of increased release of ALP into blood. It was concluded that bile acids probably play a facilitatory role in the enzymatic release of ALP from the sinusoidal surface of hepatocytes, which may be accentuated by the presence of increased amounts of ALP on the sinusoidal surface in some disease states.

Canine corticosteroid-induced alkaline phosphatase in serum was solubilized by phospholipase activity in vivo.

In this study, gas chromatography/mass spectrometry revealed the presence of stoichiometric amounts of myo-inositol in association with serum corticosteroid-induced isozyme of alkaline phosphatase (CALP) in canine serum. Such remnants are consistent with prior membrane attachment of serum CALP and its release into serum by endogenous phospholipase activity. Serum CALP was further shown to behave similarly to CALP released from hepatocyte membranes by glycosyl phosphatidylinositol phospholipase D (GPI-PLD) and differently from CALP solubilized by GPI-phospholipase C (PLC) on both native polyacrylamide gel electrophoresis and Western blot analysis using anti-cross-reacting determinant antibody. In addition to bile canalicular surfaces, CALP activity was found over hepatocyte sinusoidal surfaces by histochemical staining of canine liver sections. A significantly higher ratio of CALP to total alkaline phosphatase activity was observed in serum as opposed to bile in 10 of 11 paired serum and bile samples from dogs. This suggested that bile is not likely to be the source of serum CALP and is consistent with the release of CALP from hepatocyte basolateral surfaces directly into serum. It was concluded that serum CALP was once membrane bound and was released by phospholipase activity into serum. Our findings are consistent with release of CALP from the sinusoidal surfaces of hepatocytes into serum either by endogenous GPI-PLD activity or release by GPI-PLC followed by modification of the phosphatidylinositol remnant in vivo.

Automated and semiautomated analysis of rat alkaline phosphatase isoenzymes.

A semiautomated quantitative assay for rat serum alkaline phosphatase (ALP) isoenzyme determination was developed, incorporating selective precipitation of bone alkaline phosphatase (BALP) with wheat germ lectin and differential inhibition with levamisole for determination of intestinal alkaline phosphatase (IALP). The assays for each isoenzyme were linear over a broad range of activities. The within-run and between-run coefficients of variation were less than 11% for all 3 isoenzymes. Dilution of serum with saline results in an artifactual overestimation of BALP activity. Comparison of ALP and ALP isoenzyme activity in rats of various ages showed that BALP activity drops dramatically with increasing age of rats. IALP activity is greater in immature rats compared to that in mature rats. While there was no difference between male and female rats at 4 wk of age with regard to total ALP activity and activity of any of the isoenzymes, total ALP activity and activity of the individual isoenzymes were higher in males than in females at most ages over 4 wk. Gavage with corn oil resulted in increased serum IALP activity, and bile duct ligation resulted in increased liver alkaline phosphatase activity. This combined assay for the 3 ALP isoenzymes in rat serum is an efficient means of analysis of large numbers of samples and should increase markedly the specificity of serum ALP activity in identifying the target organ in toxicologic studies when serum ALP activity is increased.

Hepatic total 3 alpha-hydroxy bile acids concentration and enzyme activities in prednisone-treated dogs.

High serum alkaline phosphatase (ALP) activity is considered a sensitive marker of cholestasis in most mammalian species, including dogs. Induction of high serum ALP activity in association with cholestasis is dependent on high hepatic bile acids concentrations. Treatment of dogs with glucocorticoids also results in high serum ALP activity. The possible causal relation between serum ALP activity and bile acids concentration was investigated in dogs treated with glucocorticoids. The relation of glucocorticoid treatment to changes in the activity of individual ALP isoenzymes, alanine transaminase (ALT) and gamma-glutamyltransferase (GGT) also was investigated. Eight conditioned dogs were given 4 mg of prednisone/kg of body weight, i.m., daily for 10 days. Blood samples were taken prior to treatment and on treatment days 3, 5, 7, and 10. Liver tissue was then taken from each dog. Serum total ALP activity was significantly (P < 0.05) high at day 3 in prednisone-treated dogs. Isoenzyme analysis indicated that this increase was attributable to an increase in the liver ALP isoenzyme (LALP). Significant increases in serum corticosteroid-induced ALP (CALP) and bone ALP were first observed on days 7 and 10, respectively. Serum ALT and GGT activities were significantly increased by day 5. Increased serum or hepatic tissue bile acids concentrations were not observed in prednisone-treated dogs, compared with values in 8 clinically normal (control) dogs, but were high in 3 dogs with complete bile duct ligation. Hepatic activities of LALP, CALP, and GGT were higher in prednisone-treated dogs than values in controls, indicating probable increased hepatic synthesis of these enzymes. Hepatic ALT activity was not increased.(ABSTRACT TRUNCATED AT 250 WORDS)

Assessment of corticosteroid-induced alkaline phosphatase isoenzyme as a screening test for hyperadrenocorticism in dogs.

Quantitative determination of the corticosteroid-induced isoenzyme of alkaline phosphatase (CAP) was evaluated as a screening test for hyperadrenocorticism (HAC) in dogs. A series of 40 dogs with HAC (CAP range, 96 to 14,872 U/L), 30 clinically normal dogs (CAP range, 0 to 38 U/L), and 80 dogs with various diseases (non-HAC) and without history of exogenous glucocorticoid exposure for a minimum of 60 days (CAP range, 0 to 1163 U/L) were used to evaluate the test. Sensitivity and specificity of CAP was calculated at various cutoff points for absolute CAP activity and for CAP activity expressed as a percentage of total alkaline phosphatase activity. A cutoff point of 90 U/L was selected as optimal for use of this assay as a screening test for HAC. A prevalence survey then was done of all canine serum samples submitted to our diagnostic laboratory over a 3-month period, to calculate the predictive values of a positive and a negative test result in a clinical population and to determine the relative frequency and magnitude of CAP activity in dogs that had received glucocorticoids. The predictive values of a positive and a negative test result at the 90 U/L cutoff value were 21.43% (95% confidence limits, 8.3 to 40.95%) and 100% (95% confidence limit > 96%), respectively. It was concluded that CAP isoenzyme activity, determined by routine biochemical analysis by an automated levamisole-inhibition assay, could function as a screening test for HAC; however, the predictive value of a positive test result was too low to recommend the assay as a diagnostic test.(ABSTRACT TRUNCATED AT 250 WORDS)

Haptoglobin and ceruloplasmin as determinants of inflammation in dogs.

Assay procedures for determining serum haptoglobin concentration and ceruloplasmin oxidase activity in dogs were validated, and reference values were established. Serum haptoglobin concentration is reported as milligrams per deciliter of cyanmethemoglobin binding capacity, whereas serum ceruloplasmin oxidase activity was determined by use of p-phenylenediamine as substrate. Both assays were used to analyze serum samples from 288 dogs. In each dog's case record, clinical history and final diagnosis were evaluated to determine whether the dog had an inflammatory condition. Complete blood cell counts were performed in 265 dogs, using simultaneously collected blood samples. Plasma fibrinogen concentration was determined for 161 dogs. A positive correlation (P less than 0.01) for serum haptoglobin concentration and for ceruloplasmin oxidase activity, compared with WBC counts, segmented neutrophil and band neutrophil counts, and plasma fibrinogen concentration. Ceruloplasmin oxidase activity and haptoglobin concentration were up to 6 times more sensitive than fibrinogen concentration or leukocyte counts in detecting inflammation. Specificity of ceruloplasmin oxidase activity was comparable to fibrinogen concentration and leukocyte counts, whereas haptoglobin concentration was found to be slightly less specific. Specificity of haptoglobin concentration improved slightly (from 0.82 to 0.88) when dogs with a history of glucocorticoid administration were excluded from analysis. Predictive value of a negative test result (haptoglobin concentration less than 125 mg/dl; ceruloplasmin oxidase activity less than 20 IU/L) and predictive value of a positive test result for haptoglobin concentration and ceruloplasmin activity were comparable to or better than fibrinogen concentration or various oxidase leukocyte counts in detection of inflammation in a variety of disease conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

Zidovudine toxicity to cats infected with feline leukemia virus.

Feline leukemia virus (FeLV) infection of cats is a model for the acquired immunodeficiency syndrome in humans. The toxicity of zidovudine was evaluated in SPF cats experimentally infected with FeLV. At initiation of the zidovudine study, all cats were antibody positive for FeLV antigens but clinically asymptomatic. Four cats were also viremic. Thirteen, 6- to 10-month-old cats were divided into five dosage groups and given zidovudine po at 0, 7.5, 15, 30, or 60 mg/kg daily in three equally divided doses for 32 to 34 days. Titers of circulating virus antigen remained constant; however, three of six cats receiving the higher doses of zidovudine (greater than or equal to 30 mg/kg) showed an increase in antibody titers to FeLV. Administration of zidovudine resulted in a progressive anemia, dependent upon dose and time. Macrocytes were observed prior to the development of anemia and were also found in several nonanemic cats. Repeated measures regression analyses indicated that an increased dose of zidovudine was associated with decreased packed cell volume, red blood cell count, and hemoglobin. As determined from the packed cell volume, the analyses indicate that anemia is induced only by the two highest doses of zidovudine. The regression model indicates that daily doses of 60 and 30 mg/kg are expected to induce anemia by Day 4 and Day 13, respectively. Progressive absolute neutropenia was observed in the greater than or equal to 30 mg/kg groups. Histopathologic lesions consisted of marked bone marrow hypercellularity in cats given greater than or equal to 30 mg/kg zidovudine and splenic extramedullary hematopoiesis in cats given greater than or equal to 15 mg/kg. Thus, oral toxicity of zidovudine in the cat is manifested by a dose-related anemia and neutropenia as observed in humans.

Comparison of PO2, PCO2, and pH in blood collected from the femoral artery and a cut claw of cats.

A technique for collection of blood samples from the cut claw of the cat was developed. Forty-six blood samples were collected simultaneously from the cut claw and the femoral artery of 7 healthy cats. Blood gas and pH values were measured and compared. There was no difference between sample pairs for blood PO2 and PCO2, but the pH values were significantly (P less than 0.001) higher in the capillary samples (7.432 +/- 0.033) than in the samples from the femoral artery (7.419 +/- 0.031).