ULTRASTRUCTURE AND Ca^<++>-ATPASE ACTIVITY OF GAP JUNCTIONS UNDER CRYO-ELECTRON MICROSCOPIC OBSERVATION

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In order to investigate the ultrastructure and Ca^<++>-activated adenosine triphosphatase (Ca^<++>-ATPase) activity of gap junctions under near-to-native conditions, frozen thin section and isolated gap junctons from rat liver or heart were examined under a 200 kV electron microscope equipped with a cryo-transfer system. The connexon arrangement observed from a face-on view in isolated, negatively stained gap junctions revealed quite a different pattern between cryo- and conventional images, although transverse views in frozen thin section showed no notable findings on gap junction structurc. That is to say, whereas a well-ordcred hexagonal connexon arrangement could be recognizcd in conventional liver gap junction images, connexons in cryo-images did not exhibit any regularity in their arrangements. Furthermore, the average diameter of connexons in cryo-images was a little bigger than that of the conventional images. The localization of Ca^<++>-ATPase activity on isolated heart gap junctions also displayed a different appearance between cryo- and conventional images. These results suggest a structural change of isolated gap junctions during dispensable treatments, so the method of isolated gap junction observation under a cryo-elcctron microscope is considered to be very useful in detecting its near-to-native structure.
日本組織細胞化学会の論文