Methylphenidate, but not other CNS stimulants, inhibits red blood cell calcium-activated potassium efflux.
The first-order rate constant of net potassium efflux, measured in human red blood cell (RBC) suspensions by means of a K+-sensitive electrode, was increased 26 fold (from 0.0025 min-1 to 0.0656 min-1) by 0.5 microM of the calcium ionophore A 23187. Both the basal or the calcium-stimulated potassium efflux remained unchanged following the addition of different CNS stimulants (nikethamide (1 mM), pentylenetetrazol (1mM), doxapram (1 mM), strychnine (0.1 mM), picrotoxin (0.1 mM), or nomifensine (0.1 mM). Methylphenidate (10-100 microM), however, inhibited in a concentration-dependent manner the calcium-stimulated, but not the basal potassium efflux. An IC50 of 190 microM was estimated for this effect.
D002118:Calcium / Q000494:pharmacology*; D002491:Central Nervous System Agents / Q000494:pharmacology*; D003864:Depression, Chemical; D004912:Erythrocytes / Q000378:metabolism*; D006801:Humans; D007477:Ions; D008774:Methylphenidate / Q000494:pharmacology*; D011188:Potassium / Q000097:blood*
D002491:Central Nervous System Agents; D007477:Ions; D008774:Methylphenidate; D011188:Potassium; D002118:Calcium