Enzyme Immunoassay of Bovine Lactoferrin and Serum Albumin in Acid Precipitated and Ultracentrifugal Wheys

¹ Department of Animal Sciences, University of Kentucky, Lexington 40546-0215

Sandwich enzyme immunoassays were developed to facilitate the measurement of serum albumin and lactoferrin concentrations in bovine whey samples. The procedure involved a biotinylated second antibody, an avidin-peroxidase enzyme conjugate, and a reaction product whose absorbance was measured at 490 nm. For both the serum albumin and lactoferrin assays, the lower limit in sensitivity was 1 ng/ml and in the concentration range of 2 to 20 ng/d. A linear relationship existed between the logarithm of concentration and absorbance. The intraassay and interassay coefficients of variation were 8.3 and 13.5%, respectively, for the serum albumin assay, and 5.0 and 9.6% for the lactoferrin assay. The serum albumin assay showed excellent agreement with a conventional electroimmunodiffusion serum albumin assay. Qualitatively, the lactoferrin enzyme immunoassay agreed well with a lactoferrin electroimmunodiffusion assay, but the concentration values given by the enzyme immunoassay tended to be 15% lower than those given by the electroimmunodiffusion assay. From these enzyme immunoassays, whey samples prepared by acid precipitation or ultracentrifugation were found to contain similar amounts of serum albumin, but lactoferrin concentrations were roughly 25% lower in ultracentrifugal whey samples.

Key Words: bovine lactoferrin • bovine serum albumin • enzyme immunoassay

Submitted on October 16, 1989
Accepted on April 2, 1990

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