Gc. Bertran et Ba. Kotsias, BLOCKADE OF THE INWARD RECTIFIER POTASSIUM CURRENTS BY ZINC AND NICKEL IONS IN VOLTAGE-CLAMPED TOAD MUSCLES, Life sciences, 60(2), 1996, pp. 119-125
Citations number
22
Categorie Soggetti
Biology,"Medicine, Research & Experimental","Pharmacology & Pharmacy
The inward rectifier is one of the voltage-sensitive K+ channels prese
nt in several tissues: Its conductance increases under hyperpolarizati
on and decreases with depolarization. In this work we studied the effe
cts of Zn2+ and Ni2+ (5-30 mM) on the macroscopic K+ current through t
he inward rectifier system. The experiments were performed in the shor
t muscle fibers of the lumbricalis muscle of toads with a two-microele
ctrode voltage clamp technique. The fibers were equilibrated in a cont
rol solution containing 68 mM K2SO4 and then exposed to Zn2+ or Ni2+.
We found that both cations reduced in a reversible manner the current
carried by K+ ions, and this reduction was prevented by decreasing the
external pH of the solution (pH 5). The blockade of current was sligh
tly dependent on the membrane potential and time independent. Two mech
anisms may be involved in the blocking action of these cations: Zn2+ a
nd Ni2+ may either be blocking the pore of the channels or acting at a
regulatory binding site on the extracellular surface in an unspecifie
d manner.