GLUCOCORTICOID-INDUCED THE EXPRESSION OF MESSENGER-RNA AND THE SECRETION OF LIPOCORTIN-1 IN RAT ASTROCYTOMA-CELLS

The lipocortins are a family of structurally related proteins that hav e been shown to be implicated in multiple aspects of cell biology. Sub sequent research has shown that lipocortin 1 (LC1) participates in the physiological and pathological functioning of the CNS and neuroendocr ine system. In the present study, the effects of 12-O-tetradecanoylpho rbol 13-acetate (TPA), dibutyryl cyclic AMP (Bt(2)cAMP) or dexamethaso ne (DEX) on expression of LC1 were investigated by a sandwich enzyme i mmunoassay and reverse transcription polymerase chain reaction (RT-PCR ) in rat astrocytoma (C6) cells. Time-dependent experiments revealed t hat the intracellular protein content and the mRNA of rat LC1 increase d significantly 4 h after TPA (10 nM) or DEX (1 mu M) addition. TPA an d DEX elicited a prominent induction of LC1 at 10(-8) M and 10(-6) M, respectively. Bt(2)cAMP (0.5 mM) also appeared to induce, but the indu ction was not statistically significant. In addition, DEX increased th e extracellular secretion of LC1 without cytotoxicity. These results s uggest that LC1 synthesis is chemically induced and selectively releas ed from C6 cells by dexamethasone.