Experimental modulation of occluding junctions in a cultured transporting epithelium.

作者：Adolfo Martínez‐Palomo, I Meza, G. Beaty, Marcelino Cereijido · 发表于：The Journal of Cell Biology · 年份：1980 · DOI：10.1083/jcb.87.3.736 · 被引用次数：372 · 研究领域：Pancreatic function and diabetes、Photoreceptor and optogenetics research、Ion channel regulation and function

The experimental opening and resealing of occluding junctions in monolayers of cultured MDCK cells (epithelioid of renal origin) was explored by measuring changes in the electrical resistance across the monolayer and by freeze-fracture electron microscopy. As in natural epithelia, the function of occluding junctions as permeability barriers specifically depends on extracellular Ca++ concentration and fails if this ion is replaced by Mg++ or Ba++. The removal of Ca++ and the addition of EGTA to the bathing medium opened the junctions and reduced the transepithelial resistance. Resealing was achieved within 10-15 min by restoring Ca++. Quantitative freeze-fracture electron microscopy showed that junctional opening, caused by lack of Ca++, was accompanied by simplification of the pattern of the membrane strands of the occluding junction without disassembly or displacement of the junctional components. Resealing of the cellular contacts involved the gradual return to a normal junctional pattern estimated as the average number of strands constituting the junction. The occluding junctions were also opened by the addition of the ionophore A23187, suggesting that the sealing of the contacts requires high Ca++ on the extracellular side and low Ca++ concentration of the cytoplasmic compartment. The opening process could be blocked by low temperature (7.5 degrees C). Resealing did not depend on serum factors and did not require protein synthesis; therefore, it seems to be caused by reas...