INTERACTION OF 3H-OESTRADIOL WITH ANTERIOR PITUITARY NUCLEI IN A CELL-FREE SYSTEM

Abstract

ABSTRACT The uptake and retention of 3H-oestradiol by the nuclear fraction of pituitary homogenate was dependent on factors present in the 800 g-supernatant fraction. The binding of 3H-oestradiol by the nuclear fraction was competitively inhibited by unlabelled oestradiol. The nuclear fraction retained different amounts of 3H-oestradiol following incubation at 4°C, 23°C and 37°C. Significant binding occurred at each temperature, and the rate of uptake was greatest at 37°C. Radioactivity was released rapidly from the nuclear fraction at 37°C, and this could be prevented by lowering the temperature. These studies revealed that there is a cytoplasmic component as well as a temperature-dependent release mechanism which controls oestradiol uptake and retention by the nuclear fraction. Evidence was obtained indicating that the cytoplasmic component is tissue specific.