In vivo modulation of 73 kDa heat shock cognate and 78 kDa glucose-regulating protein gene expression in rat liver and brain by ethanol

Background: In cultured cells of various origin, ethanol induces the synthe sis of 70 kDa family heat shock proteins (hsp70 family), which play a role in the protection of protein traffic and secretion, as well as in cytoskele ton organization. To assess whether ethanol also can induce such genes in v ivo, we studied the behavior of hsp70, hsc73, and grp78 messenger ribonucle ic acids (mRNAs) and related proteins in the liver and brain of rats acutel y treated with ethanol. Methods: Overnight fasted Sprague-Dawley rats (220-250) were acutely treate d with a low (2 g/kg body weight) or a high (5 g/kg body weight) dose of et hanol as a 30% solution in saline or an equal volume of saline (controls) b y gastric intubation. Animals were killed at various times after treatments (3-72 hr). Messenger RNA levels for different members of hsp70 family (hsp 70; 73 kDa heat shock cognate, or hsc73; and 78 kDa glucose-regulating prot ein, or grp78) were determined by Northern blot analysis and hybridization with specific complementary deoxyribonucleic acid (cDNA) probes. The amount s of related proteins were assayed by Western blot analysis with specific a ntibodies. Autoradiograms and fluorograms were subjected to densitometric s canning. Results: Ethanol (2 g/kg) caused a slight increase in hsc73 and grp78 mRNA levels only in the liver, without enhancing the amount of proteins. Ethanol (5 g/kg) increased the level of hsc73 and grp78 mRNAs and related proteins in the liver. In the brain, the amount of hsc73 mRNA was enhanced, but thi s did not change hsc73 protein. In addition, we observed an increase in cer ebral grp78 transcript and related protein. Hsp70 gene was not induced in t he examined tissues by either dose of ethanol. Conclusions: Hepatic and cerebral hsc73 and grp78 genes are responsive to e thanol in vivo, and their activation may signal the cell's effort to counte ract the harmful action of ethanol.