EXPRESSION OF FUNCTIONAL GAP-JUNCTIONS IN CULTURED PULMONARY ALVEOLAREPITHELIAL-CELLS

Recent observations suggest that cell-cell interactions may modulate t he response of the alveolar epithelium to injury. Expression and funct ion of gap junctions were thus evaluated in isolated alveolar type II cells. Freshly isolated (day 0) type II cells expressed mRNAs for gap junctional connexins 26, 32, and 43. Whereas connexin 26 mRNA declined similar to 40% in cultured cells, connexin 32 message decreased rapid ly and was not detectable on clay 1. In contrast, connexin 43 expressi on increased 10-fold by day 3 compared with day 0. Western blot confir med a 30-fold elevation in connexin 43 protein. Connexin 45 mRNA was n ot detected. Functional gap junction-mediated calcium signal propagati on was monitored using fura 2, a calcium-sensitive dye. Membrane defor mation in a single type II cell increased intracellular calcium; the s ignal spread rapidly to neighboring cells by octanol-sensitive pathway s. Transfer of Lucifer yellow between cells also was inhibited by octa nol. These observations demonstrate functional gap junctions between c ultured alveolar epithelial cells and suggest that gap junctional expr ession and gap junction-mediated cell-cell coupling are regulated with time in culture.