Volume flow,hydraulic conductivity and electrical properties across bovine tracheal epithelium in vitro: Effect of histamine

Volume flow (J _v), potential difference (), shortcircuit current (i ₀) and electrical resistance (R) were measured simultaneously across bovine tracheal epithelium in vitro. Under basal conditions, with no applied hydrostatic or osmotic pressure gradient (P=0, =0), no spontaneousJ _v was observed. was 31±2 mV (lumen negative),i ₀ 161±8 A cm^–2 andR 202±9 cm²,n=50. When a was applied, by adding 20–80 mM sucrose into the medium bathing either the luminal or the serosal side of the tissue, a linear relationship was found between andJ _v toward the lumen or toward the serosa. The apparent hydraulic conductivity (apparentL _p) was 4.6–4.910^–6 cm s^–1 atm^–1. Histamine 10^–4 M did not induce any spontaneousJ _v under basal conditions and had no effect oni ₀ nor onR. However, histamine caused a 100% increase inJ _v elicited by sucrose gradients. It was concluded that histamine exerts a selective action on the hydraulic conductivity of bovine tracheal epithelium. Experiments using H₁-receptors antagonists (diphenhydramine, dimetindene, chloropyramine) and H₂-antagonists (cimetidine, metiamide) or a H₂-agonist (impromidine) showed that the increase ofL _p induced by histamine was mediated via H₂-receptors.Supported by the Swiss National Foundation (SNF), grant no. 3.5880.79