DEXAMETHASONE ENHANCED BY INSULIN, BUT NOT BY THYROID-HORMONES STIMULATES APOLIPOPROTEIN-B MESSENGER-RNA EDITING IN CULTURED RAT HEPATOCYTES DEPENDING ON THE DEVELOPMENTAL STAGE

The increase of hepatic apolipoprotein B (apoB) mRNA editing during ra t development was not affected by hypothyroidism. Furthermore, the add ition of 3,3',5-triiodothyronine (T-3) to cultured hepatocytes taken f rom fetal, neonatal and adult rats had no effect on apoB mRNA editing, In contrast, dexamethasone markedly stimulated apoB mRNA editing in h epatocytes taken from neonates, This effect was enhanced by the additi on of insulin, For the first time our data provide evidence that gluco corticoids together with insulin are important for the regulation of a poB mRNA editing during postnatal development, whereas thyroid hormone s are not critical for this process.