The kinetics of a non-inactivating K(+) current in alphaT3-1 pituitary gonadotropes is not affected by holding potential.
The non-inactivating K(+) currents in alphaT3-1, a gonadotroph cell line, were recorded in the presence of low intracellular free calcium concentration. The activation kinetics of the whole-cell currents and the gating charge measured from holding potential (V(HOLD)) of -10 mV, V(HOLD)=-80 mV in presence of 4-AP (4-aminopyridine), and V(HOLD)=-10 mV with a hyperpolarizing prepulse to -80 mV were similar. No difference was observed in the onset of currents elicited from the hyperpolarizing potentials, suggesting deviation from the Cole-Moore prediction of increase in the delay of current onset with increasing hyperpolarization. The data suggests that the channel opens with at least one rate-limiting voltage-dependent step, which may imply that the position of the voltage sensor is unaffected by hyperpolarization.
Tiwari
J K
JK
Molecular Biophysics Unit, Indian Institute of Science, 560012, Bangalore, India.
Sikdar
S K
SK
D015761:4-Aminopyridine / Q000494:pharmacology; D002460:Cell Line; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002478:Cells, Cultured; D006065:Gonadotropins, Pituitary / Q000378:metabolism*; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology*; D010902:Pituitary Gland / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D011188:Potassium / Q000494:pharmacology; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism*; D013997:Time Factors
D006065:Gonadotropins, Pituitary; D015221:Potassium Channels; D015761:4-Aminopyridine; D011188:Potassium