Increased response to high KCl-induced elevation in the intracellular-Ca(2+) concentration in differentiated NG108-15 cell and the inhibitory effect of the L-type Ca(2+) channel blocker, calciseptine.
Characteristics of the increasing effect for the concentration of intracellular calcium ions ([Ca(2+)](i)) by high-KCl application were investigated in the neuroblastomaxglioma hybrid NG108-15 cell line (NG108-15 cells). The present study confirmed that the increasing effect of [Ca(2+)](i) by high-KCl application in single NG108-15 cells, differentiated with dibutyryl cAMP (Bt(2)cAMP), was significantly enhanced, compared to undifferentiated cells. The following observations were made at first: (1) The response to high-KCl application, in both undifferentiated and differentiated cells, was significantly inhibited by calciseptine (CaS), an L-type Ca(2+) channel blocker, but not by N-, P- and R-type Ca(2+) channel blockers. The IC(50) values for CaS in both undifferentiated and differentiated cell was almost identical. (2) The inhibitory effect of CaS was irreversible. (3) The increasing effect for [Ca(2+)](i) by high-KCl application was completely dependent on the presence of extracellular calcium ions. (4) The increased [Ca(2+)](i) by high-KCl application under a plateau concentration was quickly decreased to basal levels when the high-KCl solution was exchanged for a high-KCl solution containing EGTA (without CaCl(2)). Together, these results suggest that the enhancement of the response effect of [Ca(2+)](i) by high-KCl application in differentiated single NG108-15 cells was mainly due to the quantitative increase of L-type voltage-sensitive calcium channels (VSCCs), which were irreversibly inhibited by CaS.
Department of Biological Chemistry, School of Pharmaceutical Sciences, Kinki University, Kowakae 3-4-1, Higashiosaka 577-8502, Japan.
Takashi
T
Imanishi
Kayoko
K
Matsushima
Akinori
A
Kawaguchi
Tetsuyuki
T
Wada
Shigeru
S
Yoshida
Seiji
S
Ichida
D000818:Animals; D003994:Bucladesine / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000378:metabolism*; D020746:Calcium Channels, L-Type / Q000378:metabolism*; D002454:Cell Differentiation; D045744:Cell Line, Tumor; D004546:Elapid Venoms / Q000378:metabolism*; D006801:Humans; D011189:Potassium Chloride / Q000378:metabolism*
D002121:Calcium Channel Blockers; D020746:Calcium Channels, L-Type; D004546:Elapid Venoms; C067971:calciseptine; D003994:Bucladesine; D011189:Potassium Chloride; D002118:Calcium