Radioreceptor assay for beta-adrenergic receptor-reactive catecholamines in serum samples.

: A procedure for effective application of ultrafiltration is described for preparation of serum catecholamine samples suitable for a sensitive radioreceptor assay. Each of the fresh serum samples unsuitable for the direct receptor assay was dialyzed by applying centrifugal force into a capsule-shaped porous core whose surface was tightly covered with a molecular filtration membrane. Interfering macromolecular serum components were left outside the capsule during the centrifugation or forced dialysis. The ultrafiltrate in the capsule was readily recovered by another centrifugation, and was found satisfactory as an assay specimen. In the radioreceptor assay system adapted to detect 30 pg per assay tube, epinephrine added to fresh serum to make the final concentration approximately 1 X 10(-8) mol/L was recovered semiquantitatively. Serum catecholamine level determined was equivalent to beta-adrenergic receptor reactivity that could be expressed in terms of (-)-epinephrine concentration.