thapsigargin and kaliotoxin

Evaluation of different types of K+ channel expression was performed in resting and PHA (phytohemagglutinine)-activated human peripheral lymphocytes (HPL) of healthy donors by means of flow cytometry. In resting peripheral lymphocytes, the application of kaliotoxin (a selective blocker for voltage-dependent K+ (K(V)) channels), K(V) resulted in pronounced depolarization of lymphocyte membrane potential, with further promotion in the presence of thapsigargin (compound discharging Ca(i) from endoplasmic reticulum). In activated HPL, the expression of various types of K+ channels was estimated utilizing cell-cycle analysis data. In contrast to the resting cells, kaliotoxin-induced depolarization of membrane potential in PHA-activated lymphocytes of the G0/G1 phase was not enhanced by thapsigargin and in PHA-activated lymphocytes of the S and G2/M phases we were able to observe repolarization of membrane potential after kaliotoxin-induced depolarization of membrane potential. Substitution of kaliotoxin for charybdotoxin (a non-selective drug blocking both K(V) and K(Ca) channels) abrogated the above effects in PHA-activated lymphocytes. Thus, K(V) channels are active in both resting and activated HPLs and K(Ca) channel expression occurs with cell-cycle progress on PHA-induced activation of peripheral lymphocytes.

Topics: Cell Cycle; Charybdotoxin; Flow Cytometry; Humans; Lymphocyte Activation; Lymphocytes; Membrane Potentials; Phytohemagglutinins; Potassium Channel Blockers; Potassium Channels; Scorpion Venoms; Thapsigargin