title: NKCC activity restores muscle water during hyperosmotic challenge independent of insulin, ERK, and p38 MAPK.
abstract: In isosmotic conditions, insulin stimulation of PI 3-K/Akt and p38 MAPK pathways in skeletal muscle inhibits Na(+)-K(+)-2Cl(-) cotransporter (NKCC) activity induced by the ERK1,2 MAPK pathway. Whether these signaling cascades contribute to NKCC regulation during osmotic challenge is unknown. Increasing osmolarity by 20 mosM with either glucose or mannitol induced NKCC-mediated (86)Rb uptake and water transport into rat soleus and plantaris skeletal muscle in vitro. This NKCC activity restored intracellular water. In contrast to mannitol, hyperosmolar glucose increased ERK1,2 and p38 MAPK phosphorylation. Glucose, but not mannitol, impaired insulin-stimulated phosphorylation of Akt and p38 MAPK in the plantaris and soleus muscles, respectively. Hyperosmolarity-induced NKCC activation was insensitive to insulin action and pharmacological inhibition of ERK1,2 and p38 MAPK pathways. Paradoxically, cAMP-producing agents, which stimulate NKCC activity in isosmotic conditions, suppressed hyperosmolar glucose- and mannitol-induced NKCC activity and prevented restoration of muscle cell volume in hyperosmotic media. These results indicate that NKCC activity helps restore muscle cell volume during hyperglycemia. Moreover, hyperosmolarity activates NKCC regulatory pathways that are insensitive to insulin inhibition.
authors.affiliation: Department of Physiology, College of Medicine, The University of Tennessee Health Science Center, Memphis, Tennessee 38163, USA.
authors.forename: Aidar R
authors.initials: AR
authors.lastname: Gosmanov
authors.forename: Edward G
authors.initials: EG
authors.lastname: Schneider
authors.forename: Donald B
authors.initials: DB
authors.lastname: Thomason
mesh_terms: D000818:Animals; D001834:Body Water / Q000378:metabolism*; D005576:Colforsin / Q000494:pharmacology; D003470:Culture Media / Q000737:chemistry / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D005947:Glucose / Q000494:pharmacology; D007328:Insulin / Q000494:pharmacology / Q000502:physiology; D007425:Intracellular Membranes / Q000378:metabolism; D007545:Isoproterenol / Q000494:pharmacology; D008353:Mannitol / Q000494:pharmacology; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000502:physiology; D018482:Muscle, Skeletal / Q000187:drug effects / Q000378:metabolism*; D009994:Osmolar Concentration; D009997:Osmotic Pressure; D010766:Phosphorylation / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D051381:Rats; D017207:Rats, Sprague-Dawley; D049994:Sodium Potassium Chloride Symporter Inhibitors; D028021:Sodium-Potassium-Chloride Symporters / Q000502:physiology*; D064506:Solute Carrier Family 12, Member 2; D048051:p38 Mitogen-Activated Protein Kinases
chemical_list: D003470:Culture Media; D004791:Enzyme Inhibitors; D007328:Insulin; D011518:Proto-Oncogene Proteins; C578879:Slc12a2 protein, rat; D049994:Sodium Potassium Chloride Symporter Inhibitors; D028021:Sodium-Potassium-Chloride Symporters; D064506:Solute Carrier Family 12, Member 2; D005576:Colforsin; D008353:Mannitol; D000242:Cyclic AMP; C494920:Akt1 protein, rat; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D005947:Glucose; D007545:Isoproterenol