RELATIONSHIP BETWEEN THE SYSTEMS RESPONSIBLE FOR UPTAKE OF 5-HYDROXYTRYPTAMINE AND OF NORADRENALINE BY HUMAN BLOOD-PLATELETS

Human blood platelets carry a high affinity, but low capacity, saturab le system for the uptake of noradrenaline, The uptake is partially Na dependent but cannot be categorised as uptake(1), It is distinct from the uptake system responsible for 5-hydroxytryptamine transport into the platelet since the selective inhibitors of the platelet uptake sys tem for 5-hydroxytryptamine (citalopram, paroxetine) differ from those for the uptake system for noradrenaline (normetanephrine, methylisopr enaline). 5-hydroxytryptamine inhibits noradrenaline uptake but with p roperties inconsistent with competition for the same uptake system whi le noradrenaline does not inhibit 5-hydroxytryptamine uptake. Neither noradrenaline nor 5-hydroxytryptamine uptake by human platelets is inh ibited by dopamine.