A COLLAGEN ENHANCER-PROMOTER CONSTRUCT IN TRANSGENIC MICE IS MARKEDLYSTIMULATED BY ETHANOL ADMINISTRATION

Type I collagen synthesis and deposition is generally indicative of ir reversible damage in alcohol-induced cirrhosis in humans, However, in rodents, ethanol alone does not readily cause hepatic fibrosis. To det ermine whether this is because of a lack of ethanol-responsive element s, an artificial enhancer construct controlling rat type I collagen ge ne transcription was prepared in transgenic mice, The gene construct, ColCAT3.6, was a chimeric sequence containing the marker chloramphenic ol acetyltransferase (CAT) gene linked to 3.5 kb of the rat alpha 1(I) 5'-flanking DNA, and 115 base pairs (bp) of transcribed collagen gene , Groups of transgenic mice were given 4 g/kg ethanol orally, twice da ily for 4 weeks. As a positive control for hepatic fibrosis, transgeni c mice mere given intraperitoneal injections of CCl4, twice weekly for 4 weeks, Livers were assayed for CAT activity, Endogenous mouse colla gen alpha 1(I) messenger RNA (mRNA) and transgene CAT mRNA were measur ed by RNase protection assays, Collagen synthesis in livers from the t ransgenic mice treated with ethanol were increased over controls, but the levels mere not significantly different. Endogenous collagen alpha 1(1) steady-state mRNA levels in ethanol-treated mice were not signif icantly different compared with saline-treated controls, However, the transgene mRNA levels in ethanol-treated animals increased approximate ly 21-fold compared with saline-treated controls, as measured by RNase protection assays, Furthermore, the transgene product as measured by CAT activity in ethanol-treated mice was significantly increased three fold over saline-treated controls. Fire conclude that the 5'-flanking region of the rat alpha 1(I) collagen gene does contain regulatory ele ments that are strongly responsive to ethanol administration.