Actions of epimers of 12-(OH)-reduced saxitoxin and of 11-(OSO3)-saxitoxin on squid axon

Toxicon. 1985;23(4):647-55. doi: 10.1016/0041-0101(85)90369-1.

Abstract

The actions of the 12 alpha-saxitoxinol, 12 beta-saxitoxinol and a C-12 ethylene thioketal derivative of saxitoxin, as well as those of 11 alpha-(OSO3)-saxitoxin, 11 beta-(OSO3)-saxitoxin and 11 alpha-(OH)-saxitoxin, have been examined on the isolated squid giant axon. Each of these analogues acted similarly to saxitoxin in blocking specifically the sodium channel. The relative potencies are: STX (1); 11 beta-(OSO3)-STX (gonyautoxin III) (0.42); 11 alpha-(OSO3)-STX (gonyautoxin II) (0.20); 11 alpha-(OH)-STX (0.10); 12 alpha-saxitoxinol (0.0021); 12 beta-saxitoxinol (0.0005). Thus, the presence of a bulky and negatively charged sulphate group on C-11 does not materially affect the biological activity of STX. Hydrogen bonding at the C-12 position is probably an important means of binding of STX to the membrane receptor site. The difference between the epimers of saxitoxinol suggests that the H in one of them may be geometrically better aligned than that in the other, with the hydrogen acceptor group in the receptor.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amphibian Proteins
  • Animals
  • Axons / drug effects*
  • Carrier Proteins / metabolism
  • Decapodiformes
  • Dose-Response Relationship, Drug
  • In Vitro Techniques
  • Ion Channels / drug effects
  • Saxitoxin / analogs & derivatives
  • Saxitoxin / metabolism
  • Saxitoxin / toxicity*
  • Sodium / metabolism
  • Stereoisomerism
  • Structure-Activity Relationship

Substances

  • Amphibian Proteins
  • Carrier Proteins
  • Ion Channels
  • saxitoxin-binding protein, Rana catesbeiana
  • Saxitoxin
  • Sodium