Veterinary diagnostic endocrinology laboratories frequently receive hemolyzed plasma, serum, or blood samples for hormone analyses. However, except for the previously reported harm done by hemolysis to canine insulin, effects of hemolysis on quantification of other clinically important hormones are unknown. Therefore, these studies were designed to evaluate effects of hemolysis on radioimmunoassay of thyroxine, 3,5,3'-triiodothyronine, progesterone, testosterone, estradiol, cortisol, and insulin in equine, bovine, and canine plasma. In the first experiment, hormones were measured in plasma obtained from hemolyzed blood that had been stored for 18 hours. Blood samples were drawn from pregnant cows, male and diestrous female dogs, and male and pregnant female horses. Each sample was divided into 2 equal portions. One portion was ejected 4 times with a syringe through a 20-gauge (dogs, horses) or 22-gauge (cows) hypodermic needle to induce variable degrees of hemolysis. Two subsamples of the blood were taken before the first and after the first, second, and fourth ejections. One subsample of each pair was stored at 2 to 4 C and the other was stored at 20 to 22 C for 18 to 22 hours before plasma was recovered and stored at -20 C. The second portion of blood from each animal was centrifuged after collection; plasma was recovered and treated similarly as was blood. Concentrations of thyroxine in equine plasma, of 3,5,3'-triiodothyronine, estradiol, and testosterone in equine and canine plasma, and of cortisol in equine plasma were not affected by hemolysis. Storage of bovine blood at either temperature and equine blood at 20 to 22 C caused progesterone concentrations to decrease (P < 0.05); the effect was not enhanced or diminished by hemolysis. Insulin concentration in equine blood decreased (P < 0.05) at both temperatures; this effect was exacerbated by hemolysis. In the second experiment, blood samples from horses and dogs were hemolyzed and plasma was immediately recovered and stored for 18 to 22 hours at 2 to 4 C or 20 to 22 C. Storage of hemolyzed equine plasma did not affect concentrations of progesterone, insulin, or thyroxine at either temperature. Whereas progesterone concentration was not affected in hemolyzed canine plasma, hemolysis decreased (P < 0.05) insulin concentration when plasma was stored at 20 to 22 C. These results emphasize the importance of examining effects of sample collection and handling procedures on hormone stability and the danger of extrapolating results of such studies from one species to another and from one hormone to another.

The present study compared leptin, adiponectin, and thyroid hormone concentrations in normal and obese dogs, and evaluated the association between leptin and adiponectin concentrations and thyroid function. The serum leptin, adiponectin, thyroid-stimulating hormone (TSH), total thyroxine (tT4), free thyroxine (fT4), triiodothyronine (T3), and cortisol concentrations were measured in 18 normal dogs (body condition score [BCS]: 4-5/9) and 16 obese dogs (BCS: 8-9/9). Leptin and T3 concentrations were higher in the obese group than the normal weight group (p 0.01 and p 0.05, respectively). In both groups, the T3 and leptin concentrations were correlated (r

Six healthy, adult horses, with normal (mean +/- SEM) baseline serum concentrations of total triiodothyronine (T3, 1.02 +/- 0.16 nmol/L), free T3 (FT3, 2.05 +/- 0.33 pmol/L), total thyroxine (T4, 19.87 +/- 1.74 nmol/L), free T4 (FT4, 11.55 +/- 0.70 pmol/L), total reverse T3 (rT3, 0.68 +/- 0.06 nmol/L), and cortisol (152.75 +/- 17.50 nmol/L), were judged to be euthyroid on the basis of response to a standardized thyroid-stimulating hormone response test. Serum concentrations of T3, FT3, T4, FT4, rT3, and cortisol were determined immediately before and every 24 hours during a 4-day period of food deprivation, when water was available ad libitum. Similar variables were measured 72 hours after refeeding. Decreases (to percentage of baseline, prefood deprivation value) in circulating T3 (42%), T4 (38%), FT3 (30%), and FT4 (24%) concentrations were maximal after 2, 4, 2, and 4 days of food deprivation, respectively (P < 0.05). Increases (compared with baseline, prefood deprivation value) in rT3 (31%) and cortisol (41%) concentrations were maximal after 1 and 2 days of food deprivation, respectively (P < 0.05). Refeeding resulted in increase in serum T4 and FT4, and decrease in rT3 and cortisol concentrations toward baseline values, after 72 hours (P < 0.05). Refeeding did not effect a return of T3 or FT3 concentration to baseline values after 72 hours (P < 0.05). Food deprivation appears to cause changes in serum concentrations of T3, FT3, T4, FT4, rT3, and cortisol in horses that are similar to those in human beings. This effect of food deprivation should be considered when results of serum thyroid hormone and cortisol assays are interpreted in the face of clinical disease. These results further emphasize the invalidity of making a clinical diagnosis of hypothyroidism on the basis of baseline, serum thyroid hormone concentrations in horses, especially if the horses have been anorectic or inappetent.

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.

Oligodendrocytes and myelin in the corpus callosum of black tremor and normal hamsters aged over 1.5 years were ultrastructurally examined to determine the myelination index (ratio of myelin thickness/diameter of axon), percentage of naked axons, and proportions of oligodendroglial subtypes (light, medium and dark). The mutant hamsters were remarkably hypomyelinated, with a low myelination index and a high proportion of naked axons, and high proportions of the dark subtypes. Serum concentrations of thyroid hormones (T sub(3) and T sub(4)) in 6-week-old mutant hamsters were 2-fold (T sub(3)) to 3-fold (T sub(4)) higher than those of age-matched normal animals. However, in the aged animals (over 1.5 years old) only T sub(4) levels of the mutant hamsters were higher in the mutant than normal hamsters. The black tremor hamsters were hypomyelinated throughout their life and high serum level of thyroid hormones might have played a role in the hypomyelination.

Potamotrygonidae is a family of freshwater stingray endemic in South America. We determined the hematological and serum biochemistry parameters of Potamotrygon motoro and Potamotrygon falkneri from Parana Basin and Potamotrygon orbignyi and Potamotrygon scobina from the Amazon Basin. Blood was collected from 55 specimens of Potamotrygon sp., and these parameters were evaluated: red blood cell count, hematocrit percent, hemoglobin concentration, leucocytes count, trombocytes count, total protein concentration, albumin, uric acid, urea, creatinine, triglycerides, cholesterol, high-density lipoprotein HDL, calcium, phosphorus, calcium/phosphorus relationship, creatine kinase CK, gamma-glutamyl transpeptidase GGT, Aspartate transaminase AST, alanine transaminase ALT, globulin, albumin/globulin relationship, alkaline phosphatase AP, sodium, chloride, potassium, triiodothyronine T3, and thyroxine T4 hormones. The hematological indices were similar for all species, except for levels of heterophils in P. orbignyi and P. scobina that were higher. Calcium, phosphorus, calcium/phosphorus relationship, sodium, potassium, chloride, AST, ALT, GGT, CK, albumin/globulin relationship, uric acid, creatinine, urea, triglycerides, HDL, T3, T4 levels had no significant difference between the species. These results suggest that there is low influence of habitat and feeding habits. AP, total protein, albumin, globulin, glucose, and total cholesterol had significant differences between the studied species. These results support the theory that stingrays migrated from the Atlantic Ocean, adapting to different conditions over time and placed themselves geographically distant from each other.