title: Ionic mechanisms of a novel neurotoxin from the sea anemone Anthopleura sp. in rat ventricular myocytes.
abstract: OBJECTIVE
  To determine the ionic mechanisms of a novel neurotoxin rhk2a obtained from the sea anemone Anthopleura sp. in rat ventricular myocytes.
  
  
  METHODS
  Whole-cell patch-clamp recording technique was used to record the sodium, calcium, and sodium-calcium exchange currents (I(Na), I(Ca, L), and I(Na-Ca), respectively) in the isolated single rat ventricular myocytes with or without rhk2a treatment.
  
  
  RESULTS
  The current-voltage (I-V) relationship for whole-cell I(Na) in the non-treated and rhk2a-treated (at the dose of 1 micromol/L) myocytes showed no significant difference (P>0.05), but the time constants for inactivation (tau(h)) were significantly greater (P<0.05) for the treated cells over the entire course of the experiment, while the time constants for activation (tau(m)) exhibited no significant difference between the two cells. The inactivation curve of I(Na) of rhk2a-treated cells was similar to that of the non-treated cells, as with the I-V relationship for whole-cell L-type calcium current (I(Ca, L) and I(Na-Ca)).
  
  
  CONCLUSIONS
  Delayed inactivation of Na(+) channel plays an important role in the positive inotropic effect of rhk2a, possibly resulting from the alteration in Na(+) channel kinetics induced by rhk2a. rhk2a does not directly affect I(Ca, L), or I(Na-Ca).
authors.affiliation: Department of Cardiology, Nanfang Hospital, First Military Medical University, Guangzhou, 510515, China.
authors.forename: Ping
authors.initials: P
authors.lastname: Ouyang
authors.forename: Chun-yu
authors.initials: CY
authors.lastname: Deng
authors.forename: Wen-hua
authors.initials: WH
authors.lastname: Liu
authors.forename: Lei
authors.initials: L
authors.lastname: Wang
authors.forename: Dong
authors.initials: D
authors.lastname: Liang
authors.forename: Wei-min
authors.initials: WM
authors.lastname: Qian
authors.forename: An-long
authors.initials: AL
authors.lastname: Xu
mesh_terms: D000818:Animals; D015220:Calcium Channels / Q000187:drug effects* / Q000502:physiology; D002316:Cardiotonic Agents / Q000494:pharmacology*; D003064:Cnidarian Venoms / Q000494:pharmacology*; D006352:Heart Ventricles; D008297:Male; D032383:Myocytes, Cardiac / Q000187:drug effects* / Q000502:physiology; D009498:Neurotoxins / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D011994:Recombinant Proteins / Q000494:pharmacology; D015222:Sodium Channels / Q000187:drug effects* / Q000502:physiology
chemical_list: D015220:Calcium Channels; D002316:Cardiotonic Agents; D003064:Cnidarian Venoms; D009498:Neurotoxins; D011994:Recombinant Proteins; D015222:Sodium Channels