EVIDENCE FOR THE EXISTENCE OF RNA OF CA-2+-CHANNEL ALPHA-2-DELTA 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 alpha1 subunit. In this study, this method was used to investigate the role of the alpha2/delta subunit. Co-injection of RNA extracted from either rabbit heart, rat brain or rat skeletal muscle (SkM) with 'antisense' oligonucleotides complementary to the alpha2/delta 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 alpha2/delta subunit RNA of Ca2+-channel. It is proposed that te oligonucleotide treatment fails to eliminate the alpha2/delta RNA because of the vast excess of endogenous alpha2/delta RNA. These results impose a limit on the use of the hybrid-arrest method.