Radioreceptor assay of serum prolactin using nitrocellulose membrane-immobilized mammary prolactin receptor

Triton-solubilized rabbit mammary prolactin (PRL) receptor was purified by concanavalin A-agarose chromatography and immobilized on a nitrocellulose membrane. Using the membrane-bound receptor and bovine serum, the serum level of PRL was determined by radioreceptor assay (RRA). The displacement curve, obtained by serial dilutions of the serum, was parallel to that obtained in the range of 0.4 and 20 ng/ml of standard bovine PRL. Serum could be included in concentrations up to 16% of the assay buffer and, thus, the detection limit of serum PRL was about 2.5 ng/ml. PRL in the serum was determined by radioimmunoassay (RIA). The ratio of the RIA and RRA estimates of PRL was 0.99 (r = +0.99, n = 55). The gel-filtration profile of serum PRL was identical to that obtained by RIA. It was concluded that membrane-bound receptor can be used for the determination of serum PRL.