H2O2 increases sheep tracheal blood flow, permeability, and vascular response to luminal capsaicin

U. M. Wells, S. Duneclift, and J. G. Widdicombe Department of Physiology, St. George's Hospital Medical School, London SW17 ORE, United Kingdom Received 15 April 1996; accepted in final form 24 September 1996. Wells, U. M., S. Duneclift, and J. G. Widdicombe. H 2 O 2 increases sheep tracheal blood flow, permeability, and vascular response to luminal capsaicin. J. Appl. Physiol. 82(2): 621-631, 1997. Exogenous hydrogen peroxide (H 2 O 2 ) causes airway epithelial damage in vitro. We have studied the effects of luminal H 2 O 2 in the sheep trachea in vivo on tracheal permeability to low-molecular-weight hydrophilic (technetium-99m-labeled diethylenetriamine pentaacetic acid; 99m Tc-DTPA) and lipophilic ([ 14 C]antipyrine; [ 14 C]AP) tracers and on the tracheal vascular response to luminal capsaicin, which stimulates afferent nerve endings. A tracheal artery was perfused, and tracheal venous blood was collected. H 2 O 2 exposure (10 mM) reduced tracheal potential difference ( 42.0 ± 6.4 mV) to zero. It increased arterial and venous flows (56.7 ± 6.1 and 57.3 ± 10.0%, respectively; n = 5, P