BLOCKADE OF ATP-SENSITIVE POTASSIUM CHANNELS IN RABBIT VENTRICULAR MYOCYTES BY SULFHYDRYL OXIDATION

The properties of sulfhydryl redox modulation of the ATP-sensitive K(K-ATP) channel have been examined in rabbit ventricular myocytes, usi ng the patch-clamp technique. The sulfhydryl oxidizing agent [5,5'-dit hio-bis-(2-nitro-benzoic acid), DTNB] inhibited channel activity, and this inhibitory effect was reversed by the disulfide reducing agent (d ithiothreitol, DTT). N-Ethylmaleimide (NEM) induced irreversible closu re of the channel. The sulfhydryl oxidizing agents (DTNB, NEM) inhibit ed the K-ATP channel only when added to the cytoplasmic side. The resu lts suggested that metabolism-induced changes in the sulfhydryl redox can also modulate K-ATP channel activity and that a modulatory site of sulfhydryl redox may be located on the cytoplasmic side of the K-ATP channel in rabbit ventricular myocytes.