Veratridine actions on two types of fast Na+ channels in human uterine leiomyosarcoma cells

Eur J Pharmacol. 1994 Dec 27;271(2-3):387-93. doi: 10.1016/0014-2999(94)90798-6.

Abstract

In human uterine leiomyosarcoma cell line (SK-UT-1B), we previously demonstrated two types of fast Na+ current (INa(f)) induced by serum, based on different time course of current decay: fast-inactivating and slow-inactivating. To further clarify the properties of these currents, we studied the effects of veratridine, which is known to modify the inactivation process of INa(f), using whole-cell voltage clamp. Bath application of veratridine (100 microM) produced a decrease in peak INa(f) (Ipeak), simultaneous with increase in the steady-state current (Iss) and tail current (Itail). These effects of veratridine were observed in only slow-inactivating INa(f). The induction of Iss and Itail was completely reversed by washout of veratridine within 5 min, whereas the decreased Ipeak did not recover even after 15 min of washout. These findings suggest that the fast Na+ channels in this cell line may have two binding sites for veratridine: a high-affinity site, involved in the decrease in Ipeak (possibly due to a decrease in conductance), and a low-affinity site, related to the appearance of Iss and Itail (due to a long opening of the channels). It is concluded that the two types of INa(f) in this cell line have different sensitivity to veratridine and the fast Na+ channels may have two binding sites for veratridine.

MeSH terms

  • Female
  • Humans
  • Leiomyosarcoma / metabolism*
  • Sodium Channels / drug effects*
  • Tumor Cells, Cultured
  • Uterine Neoplasms / metabolism*
  • Veratridine / pharmacology*

Substances

  • Sodium Channels
  • Veratridine