Comparison of the effects of xenon and halothane on voltage-dependent Ca²⁺ fluxes in rabbit T-tubule membranes

The effects of xenon and halothane on depolarization-induced ⁴⁵Ca²⁺ fluxes mediated by voltage-dependent Ca²⁺ channels were investigated in transverse tubule membrane vesicles from rabbit skeletal muscle. Halothane, in the concentration range of 0.5-2 mM, caused a significant inhibition of ⁴⁵Ca²⁺ fluxes. Xenon tested in the range of 60%-100% did not affect the ⁴⁵Ca²⁺ fluxes. Radioligand binding studies indicated that xenon and halothane have different effects on the specific binding of [³H]Isradipine to transverse tubule membranes. Halothane caused a significant inhibition on the specific binding of [³H]Isradipine. In controls and in presence of 0.5 mM halothane, B_max values were 26.9 pmole/mg and 15.1 pmole/mg, and K_D values were 238 pM and 247 pM, respectively. On the other hand, there was no effect of xenon (60%-100%) on the characteristics of [³H]Isradipine binding. In conclusion, results indicate that xenon and halothane differ in their effects on the function of voltage-dependent Ca²⁺ channels and on the specific binding of [³H]Isradipine in skeletal muscle membranes.