Evidence for the existence of RNA of Ca²⁺-channel α₂/δ subunit in Xenopus oocytes

Ba²⁺-currents (I_Ba) through voltage-dependent Ca²⁺-channels were studied in Xenopus oocytes injected with RNA from several excitable tissues, using the two-electrode voltage-clamp technique. Previous studies have shown that the expression of cardiac Ca²⁺-channels can be suppressed by an hybrid-arrest procedure that includes co-injection of the tissue-derived RNA with an 'antisense' oligonucleotide complementary to a part of RNA coding for the Ca²⁺-channel α₁ subunit. In this study, this method was used to investigate the role of the α₂/δ subunit. Co-injection of RNA extracted from either rabbit heart, rat brain or rat skeletal muscle (SkM) with 'antisense' oligonucleotides complementary to the α₂/δ subunit RNA did not substantially affect the expression of I_Ba in the oocytes. Using the Northern blot hybridization method, it was shown that native oocytes contain large amounts of α₂/δ subunit RNA of Ca²⁺-channel. It is proposed that te oligonucleotide treatment fails to eliminate the α₂/δ RNA because of the vast excess of endogenous α₂/δ RNA. These results impose a limit on the use of the hybrid-arrest method.