The significance of discontinuities frequently found in freeze-fracture replicas of the tight junction was evaluated using complementary replicas of hepatocyte junctions from control and bile duct-ligated rats. An extensive analysis of complementary replicas using rotary platinum shadowing indicates that discontinuities in the protoplasmic (P) fracture face do not represent structural breaks in the tight-junctional network. In no case did P-face discontinuities correspond with interruptions in the groove network on the complementary extracellular (E) face. Quantitative analysis of replicas shows that P-face discontinuities result in part from "transfer" of material to the complementary E face (approximately 7% of the junctional length). However, many P-face discontinuities (7-30% of the junctional length) are matched only by a groove on the complementary E face. This finding demonstrates that a significant amount of material can be lost during freeze-fracture. An analysis of junctions from bile duct-ligated rats, which are known to have an increased paracellular permeability, shows comparable transfer and loss of material. However, the number of junctional elements and the tight-junction network density was significantly reduced by bile duct ligation. These observations indicate that discontinuities in tight-junctional elements result during the preparation of freeze-fracture replicas and are not physiologically important features of the junctional barrier. Variation in the number of elements provides the best explanation for observed differences in tight-junction permeability.
Article| March 01 1983
Structural integrity of hepatocyte tight junctions.
D W Easter
J B Wade
J L Boyer
Online ISSN: 1540-8140
Print ISSN: 0021-9525
J Cell Biol (1983) 96 (3): 745–749.
D W Easter, J B Wade, J L Boyer; Structural integrity of hepatocyte tight junctions.. J Cell Biol 1 March 1983; 96 (3): 745–749. doi: https://doi.org/10.1083/jcb.96.3.745
Download citation file: