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This Article Full Text Full Text (PDF) All Versions of this Article: 297/3/L439    most recent 90268.2008v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Yang, C. Articles by Liu, L. PubMed PubMed Citation Articles by Yang, C. Articles by Liu, L.

UTP regulation of ion transport in alveolar epithelial cells involves distinct mechanisms

Lundberg-Kienlen Lung Biology and Toxicology Laboratory, Department of Physiological Sciences, Oklahoma State University, Stillwater, Oklahoma

Submitted 8 April 2008 ; accepted in final form 4 June 2009

UTP is known to regulate alveolar fluid clearance. However, the relative contribution of alveolar type I cells and type II cells to this process is unknown. In this study, we investigated the effects of UTP on ion transport in type I-like cell (AEC I) and type II-like cell (AEC II) monolayers. Luminal treatment of cell monolayers with UTP increased short-circuit current (I_sc) of AEC II but decreased I_sc of AEC I. The Cl^– channel blockers NPPB and DIDS inhibited the UTP-induced changes in I_sc (Isc) in both types of cells. Amiloride, an inhibitor of epithelial Na⁺ channels (ENaC), abolished the UTP-induced I_sc in AEC I, but not in AEC II. The general blocker of K⁺ channels, BaCl₂, eliminated the UTP-induced I_sc in AEC II, but not in AEC I. The intermediate conductance (IK_Ca) blocker, clofilium, also blocked the UTP effect in AEC II. The signal transduction pathways mediated by UTP were the same in AEC I and AEC II. Furthermore, UTP increased Cl^– secretion in AEC II and Cl^– absorption in AEC I. Our results suggest that UTP induces opposite changes in I_sc in AEC I and AEC II, likely due to the reversed Cl^– flux and different contributions of ENaC and IK_Ca. Our results further imply a new concept that type II cells contribute to UTP-induced fluid secretion and type I cells contribute to UTP-induced fluid absorption in alveoli.

short-circuit current; fluid transport