BIOSYNTHESIS OF GROWTH HORMONE-RELEASING FACTOR BY FETAL-RAT CEREBROCORTICAL AND HYPOTHALAMIC CELLS

The biosynthesis of growth hormone-releasing factor (GRF) by cerebroco rtical tissue is controversial. Although several reports have indicate d its presence in certain rat cortical areas and in cultured rat hypot halamic cells, no data exist demonstrating its biosynthesis in these a reas. In this study, we have investigated the capacity of fetal rat ce rebrocortical and hypothalamic cells in culture for synthesizing GRF. Fetal cerebrocortical and hypothalamic cells were exposed to [H-3]Arg for 48 h. Medium and cell extracts were processed and [H-3]Arg-IR-rGRF was isolated by affinity chromatography and characterized by HPLC. In tracellular [H-3]Arg-IR-rGRF from both hypothalamic and cerebrocortica l cells exhibited four major peaks, one of them coeluting with synthet ic rGRF. In cerebrocortical cultures, newly synthesized and released [ H-3]Arg-IR-rGRF showed a similar pattern to the cell content. However, in media from hypothalamic cells, higher hydrophobicity molecular for ms were absent. The data demonstrated that fetal cerebrocortical and h ypothalamic cells in primary culture synthesize GRF with similar postt ranslational processing, but with different molecular patterns of secr etion.