Radioimmunoassay of conjugated bile acids in canine and feline sera.

A solid-phase radioimmunoassay for the measurement of total conjugated bile acids was validated for use in dogs and cats. The method used an 125I-labeled iodoglycocholate tracer and polypropylene assay tubes coated with rabbit antiserum against the major conjugated bile acids. Standard solutions of sodium taurocholate provided with the kit and serial dilutions of canine and feline sera containing low, medium, and high endogenous bile acid concentrations inhibited binding of the [125I]iodoglycocholate tracer to the antibody in a parallel manner; this inhibition indicated specificity of the assay for bile acids in the serum of dogs and cats. Increased serum bile acid concentrations in animals with liver disease confirmed the biologic specificity of the assay in dogs and cats. Accuracy was shown by quantitative recovery of purified sodium taurocholate from canine and feline sera. Intra-assay precision was 7.2% to 17.3% for dogs and 8.5% to 18.5% for cats. Interassay precision was 4.8% to 17.2% for dogs and 3.5% to 11.2% for cats. The sensitivity of the assay in dogs and cats was 0.4 mumol/L. Solid-phase radioimmunoassay is a valid method for the direct measurement of total conjugated bile acids in the dog and cat, and is of value in the diagnosis of hepatobiliary disease in these species.