Growth Hormone-Releasing Factor Production by Fetal Rat Cerebrocortical and Hypothalamic Cells in Primary Culture

Abstract Recent data from our laboratory and others have shown radioimmunoassayable GRF (IR-GRF) in the rat brain cortex. In the present study the ontogenesis of immunoreactive rat (r) GRF (IR-GRF) in long term dissociated fetal rat cerebrocortical and hypothalamic cell cultures and the regulation of its secretion by potassium depolarization and calcium channelblocking agents were investigated. The chromatographic profiles of IR-rGRF from cell extracts were determined and compared with those from in vivo cerebrocortical and hypothalamic tissues. Mechanically dispersed cultured telencephalic and diencephalic cells from 17- to 21-day-old fetal rats showed a progressive increase in IR-rGRF, reaching maximum values (media plus cells) between 775–1020 (pg/mg protein) in hypothalamic cells on days 10–20 and between 450 and 950 pg/mg protein in cortical cells on days 25-30. IR-rGRF from acidic extracts of cells and adult cortical and hypothalamic tissues adsorbed onto octadecylsilyl- silica columns corresponds p...