title: Effects of Na+ and K+ on the uptake of metaraminol by rabbit ventricular slices.
abstract: 1. The ionic dependence of [(3)H]-metaraminol transport by rabbit ventricular slices was studied.2. Transport was Na(+) dependent. Choline, Li(+), K(+), Rb(+) or Cs(+) could not be substituted for Na(+).3. Transport was K(+) dependent. Rb(+) and Cs(+), but not Li, could be substituted for K(+), their relative potencies being K(+) = or >Rb(+)>Cs(+)>>Li(+). Higher concentrations of K(+), Rb(+), Cs(+) and Li inhibited [(3)H]-metaraminol transport.4. The inhibitory effects on transport of either a marked reduction in the concentration of Na(+) or of omission of K(+) were rapidly reversible on exposure of slices to Krebs solution.5. The inhibitory effect of ouabain on [(3)H]-metaraminol transport was markedly time dependent, being significantly increased by preincubation with ouabain. The inhibitory action of ouabain was not affected, however, by the Na(+) concentration present during preincubation.6. An inwardly directed Na(+) gradient did not increase [(3)H]-metaraminol transport in slices in which Na(+) pumping had been prevented by 10(-5)M ouabain, 4 degrees C, omission of K(+) or by metabolic inhibition.7. These findings provide additional evidence that the Na(+) and K(+) activated adenosine triphosphatase may participate in the transport of metaraminol and related amines. In the absence of Na(+) pumping, induced Na(+) gradients were unable to produce transport of amine as would be predicted by the co-transport model proposed by Bogdanski & Brodie (1969).
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D002586:Cesium / Q000494:pharmacology; D002794:Choline / Q000494:pharmacology; D003864:Depression, Chemical; D066298:In Vitro Techniques; D008094:Lithium / Q000494:pharmacology; D008297:Male; D008680:Metaraminol / Q000378:metabolism*; D008954:Models, Biological; D009206:Myocardium / Q000378:metabolism*; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism / Q000494:pharmacology*; D011817:Rabbits; D012413:Rubidium / Q000494:pharmacology; D012964:Sodium / Q000378:metabolism / Q000494:pharmacology*; D014316:Tritium
chemical_list: D014316:Tritium; D002586:Cesium; D010042:Ouabain; D008680:Metaraminol; D008094:Lithium; D012964:Sodium; D000251:Adenosine Triphosphatases; D012413:Rubidium; D002794:Choline; D011188:Potassium