Objective—To evaluate 4 methods used to measure plasma insulin-like growth factor (IGF) 1 concentrations in healthy cats and cats with diabetes mellitus or other diseases.
Animals—39 healthy cats, 7 cats with diabetes mellitus, and 33 cats with other diseases.
Procedures—4 assays preceded by different sample preparation methods were evaluated, including acid chromatography followed by radioimmunoassay (AC-RIA), acid-ethanol extraction followed by immunoradiometry assay (AEE-IRMA), acidification followed by immunochemiluminescence assay (A-ICMA), and IGF-2 excess followed by RIA (IE-RIA). Validation of the methods included determination of precision, accuracy, and recovery. The concentration of IGF-1 was measured with all methods, and results were compared among cat groups.
Results—The intra-assay coefficient of variation was < 10% for AC-RIA, A-ICMA, and AEE-IRMA and 14% to 22% for IE-RIA. The linearity of dilution was close to 1 for each method. Recovery rates ranged from 69% to 119%. Five healthy cats had IGF-1 concentrations > 1,000 ng/mLwith the AEE-IRMA, but < 1,000 ng/mL with the other methods. Compared with healthy cats, hyperthyroid cats had significantly higher concentrations of IGF-1 with the A-ICMA method, but lower concentrations with the IE-RIA method. Cats with lymphoma had lower IGF-1 concentrations than did healthy cats regardless of the method used.
Conclusions and Clinical Relevance—Differences in the methodologies of assays for IGF-1 may explain, at least in part, the conflicting results previously reported in diabetic cats. Disorders such as hyperthyroidism and lymphoma affected IGF-1 concentrations, making interpretation of results more difficult if these conditions are present in cats with diabetes mellitus.
Objective—To investigate the effects of twice-daily oral administration of hydrocortisone on the bile acids composition of gallbladder bile in dogs.
Animals—6 placebo-treated control dogs and 6 hydrocortisone-treated dogs.
Procedures—Dogs received hydrocortisone (median dose, 8.5 mg/kg) or a gelatin capsule (control group) orally every 12 hours for 84 days. Gallbladder bile samples were obtained via percutaneous ultrasound-guided cholecystocentesis from each dog before (day 0 [baseline]), during (days 28, 56, and 84), and after (days 28p, 56p, and 84p) treatment for differentiated quantification of unconjugated bile acids and taurine-conjugated and glycine-conjugated bile acids via high-performance liquid chromatography–tandem mass spectrometry.
Results—Treatment with hydrocortisone for 84 days resulted in significant and reversible increases in the concentrations of unconjugated bile acids (ie, cholic, chenodeoxycholic, and deoxycholic acids) and a significant and reversible decrease in the concentration of total taurine-conjugated bile acids, compared with baseline or control group values. Treatment with hydrocortisone had no effect on bile concentrations of glycine-conjugated bile acids.
Conclusions and Clinical Relevance—In dogs, hydrocortisone administration caused reversible shifts toward higher concentrations of the more hydrophobic unconjugated bile acids (chenodeoxycholic acid and deoxycholic acid) and toward lower concentrations of the amphipathic taurine-conjugated bile acids in gallbladder bile. These data suggest that similar bile acids changes could cause major alterations in gallbladder structure or function over time in hypercortisolemic dogs.