Na(+)-K(+)-ATPase activity in alveolar epithelial cells increases with cyclic stretch.
Na(+)-K(+)-ATPase pumps (Na(+) pumps) in the alveolar epithelium create a transepithelial Na(+) gradient crucial to keeping fluid from the pulmonary air space. We hypothesized that alveolar epithelial stretch stimulates Na(+) pump trafficking to the basolateral membrane (BLM) and, thereby, increases overall Na(+) pump activity. Alveolar type II cells were isolated from Sprague-Dawley rats and seeded onto elastic membranes coated with fibronectin or 5-day-conditioned extracellular matrix. After 2 days in culture, cells were uniformly stretched for 1 h in a custom-made device. Na(+) pump activity was subsequently assessed by ouabain-inhibitable uptake of (86)Rb(+), a K(+) tracer, and BLM Na(+) pump abundance was measured. In support of our hypothesis, cells increased Na(+) pump activity in a "dose-dependent" manner when stretched to 12, 25, or 37% change in surface area (DeltaSA), and cells stretched to 25% DeltaSA more than doubled Na(+) pump abundance in the BLM. Cells on 5-day matrix tolerated higher strain than cells on fibronectin before the onset of Na(+) pump upregulation. Treatment with Gd(3+), a stretch-activated channel blocker, amiloride, a Na(+) channel blocker, or both reduced but did not abolish stretch-induced effects. Sustained tonic stretch, unlike cyclic stretch, elicited no significant Na(+) pump response.
Fisher
Jacob L
JL
Department of Bioengineering, University of Pennsylvania, Philadelphia 19104, USA.
Margulies
Susan S
SS
D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D002470:Cell Survival / Q000502:physiology; D002478:Cells, Cultured; D004232:Diuretics / Q000494:pharmacology; D004847:Epithelial Cells / Q000201:enzymology; D053503:Epithelial Sodium Channels; D016326:Extracellular Matrix Proteins / Q000494:pharmacology; D005353:Fibronectins / Q000494:pharmacology; D005682:Gadolinium / Q000494:pharmacology; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology; D008297:Male; D011650:Pulmonary Alveoli / Q000166:cytology / Q000201:enzymology* / Q000293:injuries*; D011654:Pulmonary Edema / Q000209:etiology / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D012121:Respiration, Artificial / Q000009:adverse effects*; D020545:Respiratory Mucosa / Q000166:cytology / Q000201:enzymology*; D012414:Rubidium Radioisotopes; D012964:Sodium / Q000378:metabolism; D062687:Sodium Channel Agonists; D015222:Sodium Channels / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000235:genetics* / Q000378:metabolism*
D004232:Diuretics; D053503:Epithelial Sodium Channels; D016326:Extracellular Matrix Proteins; D005353:Fibronectins; D012333:RNA, Messenger; D012414:Rubidium Radioisotopes; D062687:Sodium Channel Agonists; D015222:Sodium Channels; D000584:Amiloride; D012964:Sodium; D005682:Gadolinium; D000254:Sodium-Potassium-Exchanging ATPase