Inhibitory effect of internal sodium and Hepes on the voltage-dependent potassium conductance of rat Leydig cells.
We used the whole-cell configuration of the patch-clamp technique to investigate modulation of the voltage-dependent K+ conductance of rat Leydig cells by intracellular pH, Hepes, and Na+. pH (range 6.8-7.4) has no effect on current. Removal of Na+ (from 10 to 0 mM) increases the amplitude of K+ current and abolishes the plateau effect on peak current. Reduction of Hepes (from 25 to 10 mM) increases the amplitude of K+ current and, simultaneously, shifts the threshold for current activation to the left, but the plateau of current is still present. Removal of Na+ cancels the potentiating effect of Hepes on frequency of occurrence of time-dependent inactivation of K+ current. We conclude that the blocking effect of Hepes and Na+ on K+ current may presumably involve two distinct mechanisms, but we can not exclude some cooperativity in their ability to inactivate the voltage-gated potassium conductance of rat Leydig cells.
Desaphy
J F
JF
Laboratoire de Physiologie Animale, URA CNRS 1869 Biomembranes et signalisation cellulaire, UFR Sciences, Poitiers, France.
Joffre
M
M
D000818:Animals; D002021:Buffers; D002712:Chlorides / Q000502:physiology; D006531:HEPES / Q000494:pharmacology*; D006863:Hydrogen-Ion Concentration; D015640:Ion Channel Gating; D007985:Leydig Cells / Q000502:physiology*; D008297:Male; D008564:Membrane Potentials; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000502:physiology*; D015221:Potassium Channels / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D012964:Sodium / Q000502:physiology*
D002021:Buffers; D002712:Chlorides; D015221:Potassium Channels; D012964:Sodium; D011188:Potassium; D006531:HEPES