H2O2 increases sheep tracheal blood flow, permeability, and vascular response to luminal capsaicin |
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Authors: | Wells U M; Duneclift S; Widdicombe J G |
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Abstract: | Wells, U. M., S. Duneclift, and J. G. Widdicombe.H2O2increases sheep tracheal blood flow, permeability, and vascular response to luminal capsaicin. J. Appl.Physiol. 82(2): 621-631, 1997.Exogenous hydrogenperoxide(H2O2)causes airway epithelial damage in vitro. We have studied the effectsof luminalH2O2in the sheep trachea in vivo on tracheal permeability tolow-molecular-weight hydrophilic (technetium-99m-labeleddiethylenetriamine pentaacetic acid;99mTc-DTPA) and lipophilic(14C]antipyrine;14C]AP) tracers andon the tracheal vascular response to luminal capsaicin, whichstimulates afferent nerve endings. A tracheal artery was perfused, andtracheal venous blood was collected. H2O2exposure (10 mM) reduced tracheal potential difference(42.0 ± 6.4 mV) to zero. It increased arterial andvenous flows (56.7 ± 6.1 and 57.3 ± 10.0%,respectively; n = 5, P < 0.01, paired t-test) but not tracheal lymph flow(unstimulated flow 5.0 ± 1.2 µl · min1 · cm1,n = 4). DuringH2O2exposure, permeability to 99mTc-DTPA increased from2.6 to 89.7 × 107 cm/s(n = 5, P < 0.05), whereas permeability to14C]AP (3,312.6 × 107 cm/s,n = 4) was not altered significantly(2,565 × 107cm/s). Luminal capsaicin (10 µM) increased tracheal blood flow (10.1 ± 4.1%, n = 5)and decreased venous 99mTc-DTPAconcentration (19.7 ± 4.0, P < 0.01), and these effects weresignificantly greater after epithelial damage (28.1 ± 6.0 and45.7 ± 4.3%, respectively,P < 0.05, unpairedt-test). Thus H2O2increases the penetration of a hydrophilic tracer into tracheal bloodand lymph but has less effect on a lipophilic tracer. It also enhancesthe effects of luminal capsaicin on blood flow and tracer uptake. |
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