Single ionic channels induced by palytoxin in guinea-pig ventricular myocytes.
1. Mechanisms of palytoxin-induced ion permeability were examined in isolated single ventricular cells of guinea-pig under whole-cell-attached patch clamp conditions. 2. Palytoxin (1-2 x 10(-11) M, dissolved in Tyrode solution and put in the patch electrode) induced an elementary current flowing through single channels. Direction of the current was inward and the amplitude was 0.65 +/- 0.03 pA (mean +/- s.e. mean) at the resting membrane potential. The amplitude increased linearly with membrane hyperpolarization and decreased with depolarization; the single channel conductance was 9.5 +/- 0.5 pS. 3. Palytoxin-induced single channel current was resistant to tetrodotoxin (5 x 10(-5) M) or cobalt ions (2 x 10(-3) M) and was observed under Ca-free conditions. However, no channel current was induced by palytoxin (10(-11) - 10(-9) M) dissolved in Na+-free, choline-Tyrode solution. 4. Palytoxin also induced single channel currents in Na+-free, NH4+-, Li+- or Cs+-Tyrode solution, and the slope conductances were 16.5 +/- 1.6 pS, 9.2 +/- 0.7 pS and 11.0 +/- 0.7 pS, respectively. 5. These results indicate that palytoxin forms a new type of ionic channel with unique ion selectivity and gating behaviour.
Muramatsu
I
I
Department of Pharmacology, Fukui Medical School, Japan.
Nishio
M
M
Kigoshi
S
S
Uemura
D
D
D000178:Acrylamides; D000818:Animals; D002463:Cell Membrane Permeability / Q000187:drug effects; D002794:Choline / Q000494:pharmacology; D003064:Cnidarian Venoms / Q000494:pharmacology*; D003035:Cobalt / Q000494:pharmacology; D004558:Electric Stimulation; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007473:Ion Channels / Q000187:drug effects*; D008564:Membrane Potentials / Q000187:drug effects; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D000095702:Polyether Toxins
D000178:Acrylamides; D002794:Choline; D003064:Cnidarian Venoms; D003035:Cobalt; D007473:Ion Channels; C010272:palytoxin; D000095702:Polyether Toxins