Role of Electrolytes and Glucose in the Insulin-Induced Electrochemical Effect in Sheep Pleura
Aim: Insulin induces electrochemical alterations in sheep visceral and parietal pleura, an effect abolished by the Na(+)-channel blocker amiloride and the Na(+)-K(+) pump inhibitor ouabain. The aim of this study was to further investigate the role of different electrolytes and glucose in these electrochemical changes. Materials and methods: Sheep pleural specimens were mounted in Ussing chambers. Insulin (10(-7) M) was added mesothelially in Na(+), K(+), Ca(2+)-free, low H(+) and glucose solutions. In other experiments, specimens were pretreated with K(+) and Ca(2+)-free Krebs solutions. Trans-mesothelial Resistance was determined. Results: Insulin did not increase Trans-mesothelial Resistance of visceral and parietal pleura in K(+)-free (p = 0.008 and p = 0.028 respectively), Ca(2+)-free (p = 0.006 and p = 0.012 respectively) and low glucose (p = 0.009 and p = 0.03 respectively) solutions. This effect was totally inhibited in Na(+)-free solutions or in specimens pretreated with Ca(2+)-free Krebs solution and partially inhibited, when low H(+) solutions were used (p = 0.042 for visceral and p = 0.045 for parietal). Conclusion: Insulin-induced electrochemical changes in sheep pleura are mainly associated with alterations in Na(+) and Ca(2+) concentrations. Since amiloride and ouabain abolish these electrochemical changes, it may be suggested that insulin could influence the pleural fluid recycling, mainly via the Na(+) transportation system, irrespective of the glucose content.