Thyroxine (T4), 3,5,3'-triiodothyronine (T3), and cortisol frequently are quantified in canine serum or plasma samples to aid in the diagnosis of hypothyroidism, hypoadrenocorticism, and hyperadrenocorticism. Many laboratories have established reliable references values for concentrations of these hormones in blood of clinically normal animals. However, nonpathologic factors that affect thyroidal and adrenocortical secretion may lead to misinterpretation of test results when values for individual animals are compared with reference values. The objective of the study reported here was to identify effects of age, sex, and body size (ie, breed) on serum concentrations of T3, T4, and cortisol in dogs. Blood samples were collected from 1,074 healthy dogs, and serum concentrations of the iodothyronines and cortisol were evaluated for effects of breed/size, sex, and age. Mean (+/- SEM) serum concentration of T4 was greater in small (2.45 +/- 0.06 microgram/dl)- than in medium (1.94 +/- 0.04 microgram/dl)- or large (2.03 +/- 0.03 microgram/dl)-breed dogs, the same in females (2.11 +/- 0.04 microgram/dl) and males (2.08 +/- 0.04 microgram/dl), and greater in nursing pups (3.04 +/- 0.05 microgram/dl) than in weanling pups (1.94 +/- 0.05 microgram/dl), rapidly growing dogs (1.95 +/- 0.04 microgram/dl), and young adult (1.90 +/- 0.06 microgram/dl), middle-aged adult (1.72 +/- 0.05 microgram/dl), or old adult (1.50 +/- 0.05 microgram/dl) dogs. Dogs > 6 years old had lower mean serum T4 concentration than did dogs of all other ages, except middle-aged adults. Mean serum T3 concentration in medium-sized dogs (1.00 +/- 0.01 ng/ml) was greater than that in small (0.90 +/- 0.01 ng/ml)- and large (0.88 +/- 0.01 ng/ml)-breed dogs. Serum T3 concentration was lowest in nursing (0.85 +/- 0.01 ng/ml) and weanling (0.77 +/- 0.02 ng/ml) pups, increased in rapidly growing dogs (0.99 +/- 0.01 ng/ml) and young adult dogs (1.10 +/- 0.04 ng/ml), and decreased slightly in middle-aged (0.98 +/- 0.02 ng/ml) and old (1.01 +/- 0.03 ng/ml) adult dogs. Serum T3 concentration was unaffected by sex. Mean serum cortisol concentration was greater in small (1.06 +/- 0.07 microgram/dl)- than in large (0.79 +/- 0.03 microgram/dl)-breed dogs. Serum from nursing pups 0.57 +/- 0.04 microgram/dl) contained less cortisol than did serum from older dogs (mean values greater than or equal to 0.92 microgram/dl). Serum cortisol concentration was not different between males and females. These effects of breed/size and age on serum T3, T4, and cortisol concentrations should be considered when evaluating thyroid and adrenocortical functions in dogs.

Glucose tolerance and insulin response were evaluated in 9 normal-weight and 6 obese cats after IV administration of 0.5 g of glucose/kg of body weight. Blood samples for glucose and insulin determinations were collected immediately prior to and 2.5, 5, 7.5, 10, 15, 30, 45, 60, 90, and 120 minutes after glucose infusion. Baseline glucose concentrations were not significantly different between normal-weight and obese cats; however, mean +/- SEM glucose tolerance was significantly impaired in obese vs normal-weight cats after glucose infusion (half time for glucose disappearance in serum--77 +/- 7 vs 51 +/- 4 minutes, P < 0.01; glucose disappearance coefficient--0.95 +/- 0.10 vs 1.44 +/- 0.10%/min, P < 0.01; insulinogenic index--0.20 +/- 0.02 vs 0.12 +/- 0.01, P < 0.005, respectively). Baseline serum insulin concentrations were not significantly different between obese and normal-weight cats. Insulin peak response after glucose infusion was significantly (P < 0.005) greater in obese than in normal-weight cats. Insulin secretion during the first 60 minutes (P < 0.02), second 60 minutes (P < 0.001), and total 120 minutes (P < 0.0003) after glucose infusion was also significantly greater in obese than in normal-weight cats. Most insulin was secreted during the first hour after glucose infusion in normal-weight cats and during the second hour in obese cats. The impaired glucose tolerance and altered insulin response to glucose infusion in the obese cats was believed to be attributable to deleterious effects of obesity on insulin action and cell responsiveness to stimuli (ie, glucose).

Progesterone was administered IM to 6 adult anestrous bitches at a dosage of 2 mg/kg of body weight. Serum progesterone concentrations were measured prior to progesterone administration and for 72 hours thereafter. The serum progesterone concentration time data were analyzed by use of a pharmacokinetics modeling computer program. The mean (+/- SD) peak serum progesterone concentration (34.3 +/- 7.8 ng/ml) was reached at 1.8 +/- 0.2 hours after progesterone administration. The mean serum progesterone concentration was 6.9 +/- 1.4 ng/ml at 24 hours and 2.0 +/- 0.4 ng/ml at 48 hours after progesterone administration. By 72 hours after administration, mean serum progesterone concentration was 0.9 +/- 0.2 ng/ml, which was comparable to serum progesterone concentrations prior to injection. The mean half-life of the absorption phase was 0.5 hours (range, 0.3 to 0.7 hours). The mean half-life of elimination was 12.1 hours (range, 9.5 to 13.8 hours). By analysis of the data, it was established that a dosage of 3 mg/kg, when the hormone was given IM to dogs once a day, would maintain serum progesterone concentration > 10 ng/ml.

Sarcocystis cruzi sarcocysts were isolated from eosinophilic myositis (Em)-affected and nonaffected bovine hearts. Isolates were ruptured and used to prepare a bradyzoite antigen extract from each heart. The nonaffected heart from one newborn calf contained no apparent sarcocysts when examined histologically and was used to prepare Sarcocystis-negative control antigen. Blood samples were taken from the heart approximately 20 minutes after slaughter. Serum was obtained and evaluated, using a radioimmunoassay to measure Sarcocystis-specific IgG and IgE titers. Sarcocystis cruzi extract from a heart without EM lesions was used for antigen in the radioimmunoassay. Sarcocystis-specific IgG titer ranged between 1:1,280 and 1:2,560 in EM-affected cattle and was 1:640 in nonaffected cattle. Sarcocystis-specific IgE titer ranged between 1:640 and 1:1,280 in Em-affected and nonaffected cattle. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and protein (western) immunoblot analysis were used to compare antigen extracts and serum samples from EM-affected vs nonaffected cattle. Twenty protein bands, ranging from approximately 22 to 215 kD, were detected consistently on bradyzoite blots probed with anti-bovine IgG after incubation with serum samples. Seven of these bands, 37, 44, 53, 57, 94, 113, and 215 kD, were also detected consistently on bradyzoite blots probed with monoclonal anti-bovine IgE. One additional band, 61 kD, was detected consistently on bradyzoite blots probed for IgE, but was seldom recognized when probed for IgG. Sixteen protein bands were evident in silver-stained gels of S cruzi-negative, newborn calf antigen, but none were recognized by antisera on western blots. Consistent differences were not found among antigen extracts or among serum from EM-affected vs nonaffected cattle on silver-stained gels or western blots.

A commercially available radioimmunoassay (RIA) kit for measurement of human adrenocorticotropin (hACTH) was validated for use in dogs. Assay sensitivity was 3 pg/ml. Intra-assay coefficient of variation (X 100; CV) for 3 canine plasma pools was 3.0 (mean +/- SD, 33 +/- 0.99 pg/ml), 4.2 (71 +/- 2.4 pg/ml) and 3.7 (145 +/- 3.7 pg/ml) %. Interassay CV for 2 plasma pools measured in 6 assays was 9.8 (37 +/- 3.6 pg/ml) and 4.4 (76 +/- 3.4 pg/ml) %, respectively. Dilutional parallelism was documented by assaying 2 pools of canine plasma at 3 dilutions and correcting the measured result for dilution. Corrected mean concentrations for the first pool were 33 (+/- 0.99), 36 (+/- 4.3), and 33 (+/- 6.8) pg/ml; corrected mean concentrations for the second pool were 145 (+/- 5.4), 141 (+/- 10.8) and 125 (+/- 3.4) pg/ml. Recovery of 1-39hACTH added to canine plasma (6.25, 12.5, 25.0, 50.0, and 100.0 pg/ml) was linear and quantitative (slope = 0.890, R2 = 0.961). To test whether anticoagulant or the protease inhibitor, aprotinin, influences ACTH concentration in canine plasma, ACTH was measured in canine blood collected in 4 tubes containing anticoagulant: heparin (H), heparin + 500 kallikrein inhibitor units (KIU) of aprotinin/ml (HA), EDTA (E), and EDTA + aprotinin (EA). Plasma ACTH concentration was the same when samples containing H and HA, or HA and E were compared, and was significantly (P < 0.01) lower in samples containing EA. Plasma storage at -20 C for 1 week or 1 month was not associated with significant change in ACTH concentration in canine plasma, using any of the 4 anticoagulant treatments. Plasma ACTH concentration measured after 6 months' storage at -20 C was significantly (P < 0.01) lower for all anticoagulants used. Synthetic 1-39hACTH added to canine blood was accurately recovered (88 to 109%, n = 3) from plasma containing EDTA, with or without aprotinin, whereas percentage recovery was overestimated by 18 to 91% in heparinized plasma. Plasma ACTH concentrations in EDTA-treated canine blood kept at 4 or 22 to 25 C for 15 to 90 minutes prior to centrifugation at 8 C were not significantly different. Plasma ACTH concentration in canine plasma was affected by storage tube material. Concentration of ACTH in canine plasma stored in borosilicate glass tubes for 1 week or 1 month at -70 C was significantly higher than initial ACTH values (P less than or equal to 0.01), but was unchanged over time in plasma stored in polypropylene or polystyrene tubes. Sample handling procedures affect canine plasma ACTH concentration measured by use of the RIA kit. Optimal sample handling conditions for plasma ACTH measurement in dogs include use of EDTA anticoagulant, blood collected at 20 to 25 C (room temperature) followed by centrifugation within 15 to 90 minutes, and plasma storage in plastic (not glass) tubes for not longer than 1 month at -20 C.

The effects of thyroid hormones on the serum and cutaneous fatty acid concentration profiles of dogs were evaluated. Thyroidectomized dogs had significant (P < 0.05) increases in serum oleic acid and linoleic acid concentrations, and decreases in concentration of dihomo-gamma-linolenic acid, arachidonic acid, and other elongation products of fatty acid metabolism. These changes were reversed in response to thyroid hormone replacement. Similar changes were found in cutaneous fatty acid concentration profiles. Thus, in dogs, thyroid hormones may be involved in the regulation of fatty acid delta-6-desaturase activity.

A single dose of digoxin was injected, IV, into 5 mature male turkeys (0.066 mg/kg of body weight), 8 male ducks (0.066 mg/kg), and 6 roosters (0.33 mg/kg). Twenty-three serial venous blood samples were collected before (baseline) and after the administration of digoxin to turkeys, ducks, and roosters. Plasma concentrations of digoxin were determined in duplicate by a radioimmunoassay that was validated for avian species. The plasma concentrations were best fitted by a 3 (turkeys, ducks)- and 2 (roosters)-compartment open model, with first-order elimination from the central compartment. Significant (P < 0.05) kinetic differences were determined among species. Mean half-life (t1/2) for ducks, roosters, and turkeys were 8.30 +/- 2.70 (mean +/- SD), 6.67 +/- 3.50, and 23.7 +/- 4.8 hours, respectively. The volume of distribution at steady state (V(SS)) was 14.7 +/- 2.9, 3.13 +/- 0.49, and 2.27 +/- 0.36 L/kg, and total body clearance (CL) of drug was 1.54 +/- 0.43, 0.461 +/- 0.187, and 0.136 +/- 0.022 L/h/kg for ducks, roosters, and turkeys, respectively. The mean residence time was 10.3 +/- 3.9, 8.37 +/- 4.97, and 16.8 +/- 2.2 hours, respectively. Volume of distribution at steady state and CL in ducks were several fold higher than that in turkeys. The terminal half-life of digoxin determined for ducks and roosters in this study was considerably shorter than those previously reported for several mammalian species.