LOCALIZATION OF GAP JUNCTION PROTEINS, CONNEXIN-32 AND CONNEXIN-26, IN RAT AND GUINEA-PIG LIVER AS REVEALED BY QUICK-FREEZE, DEEP-ETCH IMMUNOELECTRON MICROSCOPY

By use of site-specific antibodies against synthetic oligopeptides, we examined the localizations of the gap junction proteins connexin 32 ( Cx32) and connexin 26 (Cx26) in rat and guinea pig liver. Double-label ing immunofluorescence microscopy revealed that in guinea pig liver bo th proteins were spread throughout the liver lobules and seemed to loc alize together within the same gap junction plaque. In rat liver, co-l ocalization of both Cx32 and Cx26 in the same plaques was also suggest ed in periportal zones. Quick-freeze, deep-etch immunoelectron microsc opy showed that immunolabeling of isolated guinea pig liver gap juncti on plaques with either Cx32 or Cx26 antiserum yielded complete and den se antibody decoration of the cytoplasmic surface of the plaques. In i solated rat liver plaques, the cytoplasmic surfaces were densely decor ated with Cx32 antiserum, whereas Cx26 labeling yielded diffuse decora tion with variable intensity of the plaques. In both species we did no t observe any focal or patchy clusters of the labeling in any plaques examined. Double-labeling immunoelectron microscopy confirmed that bot h Cx32 and Cx26 are co-localized in the same gap junction plaques. The se results suggest that in hepatocytes expressing both Cx32 and Cx26, both types of gap junction proteins are not segregated but intermingle randomly within the same plaques.