Nickel inhibits the slowly activating channels of radish vacuoles.
The mechanism of inhibition by cytoplasmic nickel of slowly activating channels in radish vacuoles was investigated using the patch-clamp technique. The decrease in the macroscopic current induced by the presence of nickel in the cytoplasmic solution can be described by a Michaelis-Menten equation with an apparent dissociation constant of 0.45+/-0.03 mM. At the single-channel level, nickel moderately decreases the single-channel conductance, since the ratio between the chord conductance in the presence and in the absence of 1 mM cytosolic nickel is 0.89+/-0.06. Experiments performed to study the interaction between calcium, an activator of the channel, and nickel strongly suggest that these two ions bind to two distinct molecular sites. A simple mathematical model predicting the experimental observations is presented.
Carpaneto
Armando
A
Istituto Biofisica, Genova, C.N.R., Italy. carpaneto@icb.ge.cnr.it
D002118:Calcium / Q000494:pharmacology; D002478:Cells, Cultured; D003198:Computer Simulation; D004305:Dose-Response Relationship, Drug; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology; D007473:Ion Channels / Q000187:drug effects* / Q000502:physiology*; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D008954:Models, Biological; D009532:Nickel / Q000494:pharmacology*; D018517:Plant Roots / Q000187:drug effects / Q000502:physiology; D031224:Raphanus / Q000187:drug effects* / Q000502:physiology*; D014617:Vacuoles / Q000187:drug effects* / Q000502:physiology*
D007473:Ion Channels; D009532:Nickel; D002118:Calcium