Ion transport by sheep distal airways in a miniature chamber.
Ion transport and the electric profile of distal airways of sheep lungs were studied in a miniature polypropylene chamber with a 1-mm aperture. Small airways with an inner diameter < 1 mm were isolated, opened longitudinally, and then mounted as a flat sheet onto the 1-mm aperture where it was glued and secured with an O-ring. Both sides of the tissue were bathed with identical physiological solutions at 37 degrees C and oxygenated. Pooled data from 27 distal airways showed an inner airway diameter of 854 +/- 22 (SE) microm and a transepithelial potential difference (PD) of 1.86 +/- 0.29 mV, lumen negative. Short-circuit current (I(sc)) was 25 +/- 3.5 microA/cm(2), tissue resistance was 96 +/- 14 Omega, and conductance was 15.2 +/- 1.7 mS/cm(2). At baseline, amiloride-sensitive Na transport accounted for 51% of I(sc) (change in I(sc) = 9.7 +/- 2.6 microA/cm(2); n = 8 airways), corresponding to 0.36 microeq. cm(-2). h(-1). Treatment with 0.1 mM bumetanide did not reduce the I(sc) (n = 5 airways). Exposure to 1 microM Ca ionophore A-23187 raised the I(sc) by 9 microA/cm(2) (47%; P < 0.03; n = 6 airways). The latter effect was blunted by bumetanide. Carbachol at 1 microM provoked a biphasic response, an initial rapid rise in I(sc) followed by a decline (n = 3 airways). There was no significant increase in PD or I(sc) in response to isoproterenol or dibutyryl cAMP. The data suggest that Na absorption constitutes at least 50% of baseline transport activity. Cl or other anion secretion such as HCO(3) appears to be present and could be stimulated by raising intracellular Ca.
Al-Bazzaz
F J
FJ
Respiratory and Critical Care Section, Veterans Affairs Chicago Healthcare System-Westside Division, and Department of Medicine, University of Illinois at Chicago, 60612, USA. faiq.al-bazzaz@med.va.gov
Gailey
C
C
D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D001692:Biological Transport / Q000187:drug effects / Q000502:physiology; D001980:Bronchi / Q000166:cytology / Q000378:metabolism; D001993:Bronchodilator Agents / Q000494:pharmacology; D003994:Bucladesine / Q000494:pharmacology; D002034:Bumetanide / Q000494:pharmacology; D000001:Calcimycin / Q000494:pharmacology; D002217:Carbachol / Q000494:pharmacology; D018679:Cholinergic Agonists / Q000494:pharmacology; D015194:Diffusion Chambers, Culture / Q000379:methods*; D004232:Diuretics / Q000494:pharmacology; D004553:Electric Conductivity; D066298:In Vitro Techniques; D007476:Ionophores / Q000494:pharmacology; D007477:Ions / Q000378:metabolism*; D007545:Isoproterenol / Q000494:pharmacology; D020545:Respiratory Mucosa / Q000166:cytology* / Q000378:metabolism*; D012756:Sheep
D001993:Bronchodilator Agents; D018679:Cholinergic Agonists; D004232:Diuretics; D007476:Ionophores; D007477:Ions; D002034:Bumetanide; D000001:Calcimycin; D003994:Bucladesine; D000584:Amiloride; D002217:Carbachol; D007545:Isoproterenol