Ca2+ changes and 86Rb efflux activated by hyposmolarity in cerebellar granule neurons.
Hyposmotic swelling increased 86Rb release in cultured cerebellar granule neurons (1 day in vitro [DIV]) with a magnitude related to the change in osmolarity. 86Rb release was partially blocked by quinidine, Ba2+, and Cs+ but not by TEA, 4-AP, or Gd3+. 86Rb efflux decreased in Cl(-)-depleted cells or cells treated with DDF or DIDS, suggesting an interconnection between Cl- and K+ fluxes. Swelling induced a substantial increase in [Ca2+]i to which both external and internal sources contribute. However, 86Rb efflux was independent of [Ca2+]0, unaffected by depleting the endoplasmic reticulum (ER) by ionomycin or thapsigargin and insensitive to charybdotoxin, iberiotoxin, and apamin. Swelling-activated 86Rb efflux in differentiated granule neurons after 8 DIV, which express Ca2+-sensitive K+ channels, was not different from that in 1 DIV neurons, nor in time course, net release, Ca2+-dependence, or pharmacological sensitivity. We conclude that the swelling-activated K+ efflux in cerebellar granule neurons is not mediated by Ca2+-sensitive large conductance K+ channels (BK) as in many cell types but resembles that in lymphocytes where it is possibly carried by voltage-gated K+ channels.
Morales-Mulia
S
S
Institute of Cell Physiology, Department of Biophysics, National University of Mexico, Mexico City.
Ordaz
B
B
Quesada
O
O
Pasantes-Morales
H
H
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D048429:Cell Size / Q000502:physiology; D002478:Cells, Cultured; D002531:Cerebellum / Q000378:metabolism*; D018118:Chloride Channels / Q000037:antagonists & inhibitors; D002712:Chlorides / Q000378:metabolism; D009474:Neurons / Q000378:metabolism*; D009994:Osmolar Concentration; D011188:Potassium / Q000378:metabolism; D026902:Potassium Channel Blockers; D051381:Rats; D012414:Rubidium Radioisotopes / Q000378:metabolism*; D013997:Time Factors
D018118:Chloride Channels; D002712:Chlorides; D026902:Potassium Channel Blockers; D012414:Rubidium Radioisotopes; D011188:Potassium; D002118:Calcium