Sodium load and high affinity ouabain binding in rat and guinea-pig cardiac tissue.
An estimation of the actual Na/K-ATPase transport activity in intact cardiac cells was made by measuring the binding of [3H]-ouabain to rat and guinea-pig ventricular strips. At the low [3H]-ouabain concentration of 1 nM equilibrium binding was hardly obtained after an incubation time of five hours. Different procedures known to alter the sodium load of the cardiac preparations influenced [3H]-ouabain binding: the sodium ionophore monensin enhanced [3H]-ouabain binding, the local anaesthetic dibucaine and a reduction of external sodium ion concentration diminished [3H]-ouabain binding; [3H]-ouabain binding was similarly affected by these procedures in the rat and guinea-pig. Since [3H]-ouabain binding occurred predominantly at the high-affinity binding sites of rat myocardium under the applied experimental conditions, it was concluded that these binding sites represent Na/K-ATPase molecules involved in sodium ion transport.
Herzig
S
S
Mohr
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K
D000818:Animals; D001665:Binding Sites; D003992:Dibucaine / Q000494:pharmacology; D004558:Electric Stimulation; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008985:Monensin / Q000494:pharmacology; D009200:Myocardial Contraction / Q000187:drug effects; D009206:Myocardium / Q000378:metabolism*; D009994:Osmolar Concentration; D010042:Ouabain / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism; D051381:Rats; D012964:Sodium / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D013997:Time Factors
D010042:Ouabain; D008985:Monensin; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D003992:Dibucaine; D011188:Potassium