Terbutaline-induced triphasic changes in volume of rat alveolar type II cells: the role of cAMP.
Changes in the volume of rat alveolar type II cells (AT-II cells) induced by terbutaline, a beta(2)-agonist, were measured using video-enhanced contrast microscopy. The changes consisted of three phases: initial cell shrinkage, cell swelling, and gradual cell shrinkage. The initial cell shrinkage was Ca(2+)-dependent and was inhibited by quinine (a K+ channel blocker). The subsequent cell swelling was cAMP-dependent and was inhibited by amiloride (a Na+ channel blocker). The final cell shrinkage was cAMP-dependent and was inhibited by 5-nitro-2-(3-phenylpropylamino)-benzoate (NPPB, a Cl- channel blocker). Thus, terbutaline-induced cell volume changes were regulated by both Ca2+ and cAMP. Accumulation of cAMP alone, however, induced the Ca2+ -dependent cell shrinkage of AT-II cells and H-89 (a PKA inhibitor) inhibited terbutaline-induced cell volume changes. This suggests that cAMP accumulation stimulates the Ca2+ signal during terbutaline stimulation. In conclusion, terbutaline stimulates not only Na+ influx, but also K+ and Cl- release mediated via cAMP accumulation in rat AT-II cells, which induces the triphasic cell volume changes.
Hosoi
Keita
K
Department of Internal Medicine, Osaka Medical College, Takatsuki, 569-8686 Japan.
Min
Kyong-Yob
KY
Shiima
Chisa
C
Hanafusa
Toshiaki
T
Mori
Hiroshi
H
Nakahari
Takashi
T
D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D048429:Cell Size / Q000187:drug effects; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism*; D015759:Ionomycin / Q000494:pharmacology; D008297:Male; D018715:Microscopy, Video / Q000379:methods; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology; D011650:Pulmonary Alveoli / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D011803:Quinine / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D015222:Sodium Channels / Q000187:drug effects / Q000502:physiology; D013726:Terbutaline / Q000494:pharmacology*; D019284:Thapsigargin / Q000494:pharmacology
D000318:Adrenergic beta-Agonists; D015221:Potassium Channels; D015222:Sodium Channels; D005576:Colforsin; D015759:Ionomycin; D019284:Thapsigargin; D000584:Amiloride; D011803:Quinine; D000242:Cyclic AMP; D013726:Terbutaline; D002118:Calcium