PLASMA-CORTISOL RESPONSES TO 3 CORTICOTROPIC PREPARATIONS IN NORMAL DOGS

Objective To compare cortisol responses to three corticotrophic prepar ations in normal dogs. Animals Eight clinically normal dogs (four inta ct males, four intact females) of medium size. Procedures Each dog rec eived four treatments on four separate occasions in a duplicated Latin square pattern. Treatments were two adrenocorticotrophin (ACTH) prepa rations given intramuscularly at 2.2 U/kg, one of the ACTH preparation s given intramuscularly at 1 U/kg and a synthetic polypeptide with ACT H-like activity (tetracosactrin, cosyntropin) given intravenously at 5 mu g/kg. Plasma samples were taken for cortisol assay before and at 0 .5, 1, 2 and 4 h after treatment. Results Plasma cortisol concentratio ns were similar with the two ACTH preparations and at both dose rates. Tetracosactrin produced smaller mean peak cortisol concentrations, wh ich tended to occur earlier than with ACTH, and smaller values for the area under the curve of plasma cortisol concentration from zero time to 4 h. Conclusion The findings suggest that canine adrenal function c an be tested adequately by giving ACTH intramuscularly at 1 U/kg and m easuring plasma cortisol in samples taken at 0 and 2 h, or by giving t etracosactrin intravenously at 5 mu g/kg and determining cortisol conc entration at 0 and 1 h.