Rainbow trout gill epithelial cells in primary culture communicate throughgap junctions as demonstrated by dye-coupling

Communication across gap junctions between cells in various tissues is cons idered an important mechanism for control of cellular growth, differentiati on and function. Although cell-cell coupling in the gill epithelium is like ly for functional reasons, the common view is that gap junctions are not pr esent between cells in the gill epithelium of teleostean fish. Gap junction mediated cell-cell communication was analysed in the present study in prim ary and secondary cultures of rainbow trout gill epithelial cells by microi njecting the fluorescent dye Lucifer yellow CH. In 4-14 day old primary and secondary cell cultures, 58% of the cells injected with Lucifer yellow wer e coupled to at least one other cell. To exclude the possibility that inter cellular dye transfer occurred through cytoplasmic bridges instead of gap j unctions, we also microinjected FITC-dextran, which because of its molecula r size does not pass through gap junctions. None of the cells injected with FITC-dextran showed spreading of the dye. The number of cells spreading Lu cifer yellow was decreased in a dose-dependent way when the cells were trea ted with dioctanoylglycerol, a synthetic diacylglycerol known to affect the open state of gap junctions, which further supports that the cells are cou pled through functional gap junctions.