Effects of oxygen radical scavengers on connexins 32 and 26 expression in primary cultures of adult rat hepatocytes.

Although we recently reported our success in inducing and maintaining the gap junction proteins connexin 26 (Cx26) and connexin 32 (Cx32) in adult rat hepatocytes cultured in serum-free L-15 medium supplemented with epidermal growth factor, dimethylsulfoxide (DMSO) and glucagon, the mechanisms by which DMSO induces gap junctions are still not clear. It is known that DMSO is not only a differentiation reagent for various cells but also a powerful scavenger of oxygen radicals. In the present study, by using this culture system and the measurement of oxidative stress by the nitro blue tetrazolium (NBT) formazan assay, we have examined the effect of oxygen radical scavengers such as DMSO, dimethylthiourea (DMTU) and alpha-tocopherol on the expression of both Cxs and on gap junctional intercellular communication (GJIC), as compared to another differentiation reagent, hexamethylene-bis-acetamide (HMBA). DMSO and DMTU clearly inhibited the oxidative stress of the cultured hepatocytes, while alpha-tocopherol and HMBA did not. The expression of Cx26 and Cx32 in the cultured hepatocytes was markedly induced by DMSO and DMTU. Furthermore, extensive GJIC was also observed with DMSO and DMTU. These results suggest that the expression of gap junctions in the hepatocytes may be closely related to oxidative stress and that oxygen radical scavengers may be important substances in inducing this expression.