Radioreceptor assay for prolactin and other lactogenic hormones.

A radioreceptor assay with a sensitivity of 5 nanograms per milliliter has been developed for mammalian and avian pituitary prolactin, placental lactogenic hormones, and humnan growth hormone, using a membrane receptor preparation isolated from rabbit mammary glands. Prolactin preparations inhibited the binding of [(125)I]prolactin to receptors in direct proportion to the biological potency of these preparations. Thus, the radioreceptor assay provides a convenient and simnple assay for hormones which have lactogenic activity.