Roles of Ca 2+ and Protein Tyrosine Kinase in Insulin Action on Cell Volume via Na + and K + Channels and Na + /K + /2Cl − Cotransporter in Fetal Rat Alveolar Type II Pneumocyte
| Autor: | Hugh O'Brodovich, Yoshinori Marunaka, Naomi Niisato, A. K. Tanswell, Martin Post |
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| Rok vydání: | 1999 |
| Předmět: |
Epithelial sodium channel
Potassium Channels Physiology Pregnancy in Diabetics Sodium Channels Amiloride chemistry.chemical_compound Pregnancy Insulin Enzyme Inhibitors Phosphorylation Egtazic Acid Bumetanide Chelating Agents Quinine Chemistry Protein-Tyrosine Kinases Thapsigargin Female Intracellular Signal Transduction medicine.drug medicine.medical_specialty Sodium-Potassium-Chloride Symporters Biophysics Calcium-Transporting ATPases Phenols Internal medicine medicine Extracellular Animals Humans Rats Wistar Na+/K+-ATPase Cell Size Respiratory Distress Syndrome Newborn Infant Newborn Cell Biology Molecular biology Receptor Insulin Rats Pulmonary Alveoli Endocrinology Calcium Carrier Proteins Cotransporter Protein Processing Post-Translational |
| Zdroj: | Journal of Membrane Biology. 168:91-101 |
| ISSN: | 1432-1424 0022-2631 |
| DOI: | 10.1007/s002329900500 |
| Popis: | The aim of the present study was to investigate the roles of Ca2+ and protein tyrosine kinase (PTK) in the insulin action on cell volume in fetal rat (20-day gestational age) type II pneumocytes. Insulin (100 nm) increased cell volume in the presence of extracellular Ca2+ (1 mm), while cell shrinkage was induced by insulin in the absence of extracellular Ca2+ (1 nm). This insulin action in a Ca2+-containing solution was completely blocked by co-application of bumetanide (50 microm, an inhibitor of Na+/K+/2Cl- cotransporter) and amiloride (10 microm, an inhibitor of epithelial Na+ channel), but not by the individual application of either bumetanide or amiloride. On the other hand, the insulin action on cell volume in a Ca2+-free solution was completely blocked by quinine (1 mm, a blocker of Ca2+-activated K+ channel), but not by bumetanide and/or amiloride. These observations suggest that insulin activates an amiloride-sensitive Na+ channel and a bumetanide-sensitive Na+/K+/2Cl- cotransporter in the presence of 1 mm extracellular Ca2+, that the stimulatory action of insulin on an amiloride-sensitive Na+ channel and a bumetanide-sensitive Na+/K+/2Cl- cotransporter requires Ca2+, and that in a Ca2+-free solution insulin activates a quinine-sensitive K+ channel but not in the presence of 1 mm Ca2+. The insulin action on cell volume in a Ca2+-free solution was almost completely blocked by treatment with BAPTA (10 microm) or thapsigargin (1 microM, an inhibitor of Ca2+-ATPase which depletes the intracellular Ca2+ pool). Further, lavendustin A (10 microm, an inhibitor of receptor type PTK) blocked the insulin action in a Ca2+-free solution. These observations suggest that the stimulatory action of insulin on a quinine-sensitive K+ channel is mediated through PTK activity in a cytosolic Ca2+-dependent manner. Lavendustin A, further, completely blocked the activity of the Na+/K+/2Cl- cotransporter in a Ca2+-free solution, but only partially blocked the activity of the Na+/K+/2Cl- cotransporter in the presence of 1 mm Ca2+. This observation suggests that the activity of the Na+/K+/2Cl- cotransporter is maintained through two different pathways; one is a PTK-dependent, Ca2+-independent pathway and the other is a PTK-independent, Ca2+-dependent pathway. Further, we observed that removal of extracellular Ca2+ caused cell shrinkage by diminishing the activity of the amiloride-sensitive Na+ channel and the bumetanide-sensitive Na+/K+/2Cl- cotransporter, and that removal of extracellular Ca2+ abolished the activity of the quinine-sensitive K+ channel. We conclude that the cell shrinkage induced by removal of extracellular Ca2+ results from diverse effects on the cotransporter and Na+ and K+ channels. |
| Databáze: | OpenAIRE |
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