SPECIFIC-INHIBITION OF NA-CA EXCHANGE FUNCTION BY ANTISENSE OLIGODEOXYNUCLEOTIDES

The Na-Ca exchanger is essential for the Ca2+ homeostasis in many cell types, This transporter has been difficult to investigate because no specific inhibitor is available, We have synthesized an antisense olig odeoxynucleotide directed against the rat cardiac Na-Ca exchanger mRNA , To estimate the activity of the Na-Ca exchange in single cultured my ocytes, the exchange current (I-NaCa) was measured with the voltage-cl amp technique while the intracellular Ca2+ concentration ([Ca2+](i)) w as simultaneously recorded, Most cells exposed to antisense oligodeoxy nucleotide showed neither an I-NaCa nor an increase of [Ca2+](i) upon extracellular Na+ removal, Liberation of Ca2+ by flash-photolysis of c aged Ca2+ was not followed by a decay of [Ca2+](i) in cells exposed to the antisense oligonucleotide, whereas in control cells resting [Ca2](i) was reached 6 s after the flash, Control experiments with non-sen se and mismatched oligonucleotides were performed to exclude unspecifi c inhibitory effects, These results demonstrate that the Na-Ca exchang e,vas specifically and completely suppressed and that antisense oligod eoxynucleotides represent a useful tool to investigate the cellular an d molecular properties of the Na-Ca exchanger.