Madden M E, Sarras M P
Dev Biol. 1985 Dec;112(2):427-42. doi: 10.1016/0012-1606(85)90415-4.
The role of tight junctions (zonula occludens) in the formation of apical plasma membrane (PM) domains was investigated in the embryonic rat pancreas. In the present study, lectin-rhodamine (WGA-TRITC and RCAII-TRITC) and lectin-gold (WGA-Au and RCAII-Au) conjugates were used to monitor apical PM domain formation and freeze-fracture analysis was used to monitor tight junction formation in the pancreatic epithelium of embryonic, neonatal, and adult rats. Fluorescent and TEM analysis of WGA and RCAII binding indicated that an apical PM domain is formed as early as Day 13 of gestation in the pancreatic epithelium. While apical WGA binding remained into adult life, RCAII binding was lost by 1 day after birth. In contrast, tight junctions were not observed until Day 14 of gestation. At this time, tight junctions were found to be incomplete in formation and typically consisted of linear arrays of IMPs or discontinuous arrays of sealing strands (focal adherens). Continuous tight junctions were not completely formed until Day 15 of gestation. Continued development of tight junctions during gestation was characterized by (1) an increase in the number of sealing strands and (2) a more parallel arrangement of sealing strands within each junctional complex. By 8 weeks after birth, tight junctions were more loosely organized and contained fewer sealing strands as compared to that observed in the fetus. These results suggest that lateral diffusion of apical PM glycoconjugates may be restricted even in the absence of complete tight junctional complexes during development of the rat pancreas.
