Erythrocyte shunting patterns are identical for endothelial dysfunction and for loss of connexin 43

Abstract

To study shunting (preferential flow pathways), we observed arterioles in the hamster cheek pouch by intravital microscopy (pentobarbital 70mg/kg, N=48). Erythrocyte (RBC) fluxes into sequential branches (4–8) from a central feed were measured (fluorescently labeled RBC). In controls, each branch received 10–25% of total inflow. Preconditioning, either with nitroprusside or controlled thermal injury (50°C, 20s) by microcautery (300μm), induced shunting, with 80–90% of RBCs passing along the central feed to one distal branch. Endothelial dysfunction induced with tissue bath nitro‐arginine (10‐5M) led to the same shunting pattern, as did tissue blockade of gap junctions (18‐alpha‐GA, Gap‐27(43), sucrose). Cx43 was targeted for knock‐down using RNAi applied to the cheek pouch 3 days in advance, decreasing Cx43/GAPDH protein by 60%. Shunting was seen in all RNAi(Cx43) animals, but not with RNAi(Cx45) treatment. Dilations to bradykinin (10‐7M), acetylcholine (10‐6M), isoproterenol (10‐5M) and adenosine (10‐4M) were attenuated in preconditioning, indicating endothelial dysfunction. Thus, a common maldistribution of RBC fluxes is seen both in the absence of gap junctional activity and in the preconditioned state, and may occur in many pro‐inflammatory states associated with endothelial dysfunction. (NIH HL55492; AHA 0655908T)