Size Heterogeneity of Rat Prolactin Secreted in Vitro: Effect of Incubation Time and Dopamine

Abstract

Culture medium harvested at various times (1, 2, and 6 hr) during the incubation of hemipituitary fragments from ovariectomized estrogen-treated rats was subjected to Sephadex G-100 gel filtration chromatography and the radioimmunoassayable prolactin was determined in the eluted fractions. Three heterogeneous forms of the hormone were found in the medium. As incubation time progressed, the level of the two larger components decreased. Dopamine (1 × 10-6M) added to the incubation medium either during the first or third to sixth hours of incubation had no effect on the relative quantities of the heterogeneous forms being released into the medium.