Adamsen, J.

Lind, Peter

Lund, Regina Teresa

Løvendahl, P.

A noncompetitive, time-resolved immunofluorometric assay (TRIFMA) was developed using a selected pair of monoclonal antibodies (mab) raised against recombinant bovine GH, with the catching mab immobilized on microtiter plate wells and the detection mab labeled with Eu3+ as a tracer, arranged as a sandwich. Plates were coated, with mab1.15 (680 ng/well) using a phosphate buffer (pH 4.9), and then blocked with assay buffer containing 1% (wt/vol) BSA. The assay procedure involved incubation of 50 muL of sample (plasma or serum) and 200 muL of assay buffer containing 25 ng of mab1.2-Eu3+ conjugate for 4 h at 25degreesC. Plates were then washed six times, incubated for 5 to 10 min with 250 muL of enhancement solution, and fluorescence read with a time-resolved fluorometer. The sensitivity of the assay was 0.1 ng/mL, and the working range was 0.2 to 200 ng/mL. Recovery of quantitative amounts of bovine GH added to plasma samples was close to 100%. Cross-reactivity with other bovine pituitary hormones or with GH from nonbovidae or cervidae species was not significant. Intra- and interassay CV during routine operation was 4.4 and 10.7%, respectively (mean = 3.54 ng/mL). Plasma concentrations of bovine GH determined by TRIFMA correlated closely (r(2) greater than or equal to 0.93) with RIA results, with a conversion ratio of 0.62 when the higher specificity of the monoclonal antibodies was taken into account. The TRIFMA is a reliable alternative to RIA methods because the assay employs no radiolabeled or hazardous chemicals, delivers results rapidly, and has little risk of down periods

Technical note: Time-resolved immunofluorometric assay for growth hormone in ruminants

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