Insulin-Induced Electrochemical Changes in Pleura are Associated with the Location within the Pleural Cavity

Aim: We investigated the effects of insulin on the electrophysiology of sheep pleural specimens obtained from the upper and lower parts of the pleural cavity and the insulin receptor abundance in these regions. Materials and methods: Sheep pleural specimens were obtained from the upper and lower lung lobes and from the 1(st)-4(th) and 8(th)-12(th) ribs and were mounted between Ussing chambers. Insulin 10(-7)M was added on the mesothelial surface with Insulin Receptor (IR) inhibitor in some experiments. Trans-mesothelial Resistance (R(TM)) was determined. Immunohistochemistry for the presence of IR differences was performed. Results: Insulin increased the R(TM) of all pleural regions. Higher R(TM) increase was demonstrated in lower lobe visceral and in caudal parietal specimens. The R(TM) increase demonstrated in caudal parietal had the tendency to be higher than that observed in the lower lobe visceral specimens. IR inhibitor abolished insulin's effect in all regions. Immunostaining was more intense for parietal and for caudal parietal specimens when compared with the visceral and lower lobe visceral specimens. Conclusion: Insulin induces electrochemical alterations that vary depending on the location of specimens within the pleural cavity which possibly is not correlated with insulin receptors variations