Calcium-dependent, swelling-activated K+ conductance in human neuroblastoma cells.
In most mammalian cells, regulatory volume decrease (RVD) is mediated by swelling-activated Cl(-) and K(+) channels. Previous studies in the human neuroblastoma cell line CHP-100 have demonstrated that exposure to hypoosmotic solutions activates Cl(-) channels which are sensitive to Ca(2+). Whether a Ca(2+)-dependent K(+) conductance is activated after cell swelling was investigated in the present studies. Reducing the extracellular osmolarity from 290 to 190 mOsm/kg H(2)O rapidly activated 86Rb effluxes. Hypoosmotic stress also increased cytosolic Ca(2+) in fura-2 loaded cells. Pretreatment with 2.5 mM EGTA and nominally Ca(2+) free extracellular solution significantly decreased the hypoosmotically induced rise in cytosolic Ca(2+) and the swelling-activated 86Rb efflux. In cell-attached patch-clamp studies, decreasing the extracellular osmolarity activated a K(+) conductance that was blocked by Ba(2+). In addition, the swelling-activated K(+) channels were significantly inhibited in the presence of nominally free extracellular Ca(2+) and 2.5mM EGTA. These results suggest that in response to hypoosmotic stress, a Ca(2+)-dependent K(+) conductance is activated in the human neuroblastoma cell line CHP-100.
Basavappa
Srisaila
S
Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, CT 06520, USA. srisaila_basavappa@urmc.rochester.edu
Mangel
Allen W
AW
Boulpaep
Emile L
EL
D001464:Barium / Q000737:chemistry; D002118:Calcium / Q000378:metabolism*; D002614:Chelating Agents / Q000494:pharmacology; D004533:Egtazic Acid / Q000494:pharmacology; D004594:Electrophysiology; D006801:Humans; D009447:Neuroblastoma / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000737:chemistry / Q000378:metabolism*; D013312:Stress, Physiological; D013997:Time Factors; D014407:Tumor Cells, Cultured; D014867:Water / Q000737:chemistry
D002614:Chelating Agents; D014867:Water; D001464:Barium; D004533:Egtazic Acid; D011188:Potassium; D002118:Calcium