PROLACTIN OF APPARENT LARGE MOLECULAR SIZE: THE MAJOR IMMUNOACTIVE PROLACTIN COMPONENT IN PLASMA OF A PATIENT WITH A PITUITARY TUMOR1

Abstract

Multiple immunoactive components of circulating human prolactin were detected in each of six plasma samples analyzed by assay of fractions from Sephadex G–100 chromatography. Prolactin of apparent large molecular size (K_av ≃ 0.2) was the major (70%) circulating immunoactive prolactin in a patient with a pituitary tumor and acromegaly. Much less (av 0.2 prolactin was detected in the other 5 plasma samples, drawn from volunteers before and after administration of synthetic TRF, during pregnancy and postpartum lactation, and from a patient with a chromophobe adenoma and galactorrhea. In these 5 plasmas, the major (80–90%) immunoactive prolactin component (K_av ≃ 0.4) was not distinguishable chromatographically from monomeric pituitary prolactin.