The effects of cyanide on intracellular ionic exchange in ferret and rat ventricular myocardium.
The effects of cyanide on Ca2+ exchange in isolated ventricular myocytes and on the intracellular concentrations of Ca2+, Na+ and H+ have been investigated to assess the contribution that mitochondria might play in cellular Ca2+ metabolism. Ionic levels were measured with ion-selective electrodes. KCN (2.5 mM) inhibited a component of Ca2+ exchange in myocytes that could be attributed to mitochondrial exchange, but was without effect on non-mitochondrial Ca2+ exchange. NaCN (2.5 mM) caused a transient reduction of [H+]i, [Na+]i and [Ca2+]i when applied to the superfusate bathing ventricular trabeculae or papillary muscles. The transient changes of [Na+]i were accentuated when the preparation was exposed to a solution which would be expected to increase the cellular calcium content. The reduction of [Na+]i which accompanies a reduction of the extracellular sodium concentration, [Na]o, was attenuated in the presence of NaCN, but the intracellular acidosis resulting from a reduction of [Na]o was unaffected by NaCN. A small, but significant, rise of [Ca2+]i accompanied a reduction of [Na]o but only when NaCN was present in the superfusate. It is concluded that cyanide ions have a reasonably specific action on cardiac cellular ionic metabolism. Its primary action is to prevent mitochondrial Ca2+ sequestration. It is postulated that a Na+/H+ exchange, possibly at the sarcolemma, could account for some of the changes to sarcoplasmic ionic levels observed. In a solution of low [Na]o, it is concluded that mitochondria could sequester at least 30% of the calcium accumulated by the cell even though the sarcoplasmic [Ca2+] does not exceed 0.3 microM.
D000818:Animals; D002118:Calcium / Q000378:metabolism; D003486:Cyanides / Q000494:pharmacology*; D005289:Ferrets; D006352:Heart Ventricles / Q000187:drug effects / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007477:Ions; D007700:Kinetics; D008274:Magnesium / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism*; D010101:Oxygen Consumption / Q000187:drug effects; D011188:Potassium / Q000378:metabolism; D051381:Rats; D012964:Sodium / Q000378:metabolism; D012966:Sodium Cyanide / Q000494:pharmacology*; D013045:Species Specificity
D003486:Cyanides; D007477:Ions; D012964:Sodium; D008274:Magnesium; D012966:Sodium Cyanide; D011188:Potassium; D002118:Calcium