PROGRESSIVE DEVELOPMENT OF GAP-JUNCTIONS DURING GROWTH OF HUMAN PANCREATIC DUCT CELLS (CAPAN-1) IN-VITRO AND IN-VIVO

Among their numerous functions, gap junctions play a crucial role in p roliferation, differentiation and secretion processes, although their existence and potential role in ion secretion in human pancreatic duct s have yet to be established. To investigate the morphogenesis and the role of gap junctions in human pancreatic duct cells, the Capan-1 cel l line maintained in culture or heterotransplanted into nude mice was employed as model system. Capan-1 cells polarize during their growth i n vivo and in vitro forming duct-like structures. Furthermore in cultu re, after confluence, these cells form domes, which is indicative of i on exchange processes. After treatment with tannic acid and freeze-fra cture, gap junctions were observed along the basolateral membranes of Capan-1 cells on electron microscopic examination. The presence of alk aline phosphatases on gap junctions was demonstrated cytoenzymatically . In addition, cell-to-cell communication was visualized by microinjec tion of Lucifer yellow. During differentiation of Capan-1 cells in cul ture, the frequency of intercellular communications increased markedly over the period (days 11-13) when the cells form duct-like structures . The increase in gap junctions was demonstrated by analysis of the po larized cells organized in duct-like structures that are commonly obse rved in the tumors formed by heterotransplantation of Capan-1 cells in to nude mice. Furthermore, gap junctions associated with tight junctio ns were also observed in the cells forming such structures. The role o f gap junctions in ion exchange was evaluated by counting the number o f domes in cultures treated with heptanol. Heptanol (an uncoupling age nt of gap junction communication) completely inhibited dome formation in a reversible way, and reduced the frequency of intercellular commun ications by 44%. These results suggest that the gap junctions expresse d by Capan-1 cells are involved in ion secretion by the human cancerou s pancreatic duct cell line, Capan-1. In the present study, we show th at: i) the expression of gap junctions is linked to development of the spatial conformation of the cells; and ii) gap junctions may be invol ved in ion secretion.