An improved method of purifying inhibin radioligand for radioimmunoassay.

Polyacrylamide gel electrophoresis (PAGE) separation of bovine inhibin from free iodine after iodination is described. Previous methods of separation typically relied upon a G25 gel filtration and Matrix gel Red A affinity column chromatography protocol. When compared to column chromatography, PAGE-purified radiolabelled inhibin resulted in significantly increased binding (13.1% vs. 7.5%) and enhanced sensitivity (ED50 = 92 microliters inhibin standard vs. ED50 = 198 microliters inhibin standard) to the inhibin antibody #1989. Our results demonstrate an advantageous approach to purifying 31,000 Mr bovine inhibin radioligand after iodination for RIA.