Effect of Hypothalamic Extracts on the Incorporation of [ 3 H]-Thymidine by Pituitary Cells in Culture

Abstract

Summary

Rat hypothalamic extracts stimulated the incorporation of [³H]-thymidine into DNA derived from cultured rat pituitary cells, after 24 hr and 48 hr of incubation. A three- to fivefold increase in the incorporation of [³H]-thymidine was observed in the presence of hypothalamic extracts. This stimulatory activity was significantly decreased by heating or dialysis. Rat cerebral cortical extracts also stimulated this incorporation but to a lesser extent than hypothalamic extracts. Hydroxyurea (25 mM) completely inhibited the incorporation of [³H]-thymidine by pituitary cells. The synthetic hypothalamic hormones, LHRH, TRH, and somatostatin, had no significant effects, whereas estradiol (40 nM) had a significant inhibitory effect.