title: Platelet 5-hydroxytryptamine transport, an electroneutral mechanism coupled to potassium.
abstract: Transport of 5-hydroxytryptamine into plasma membrane vesicles isolated from porcine blood platelets is stimulated when a potassium gradient (in greater than out) is imposed across the vesicle membrane. This stimulation occurs in the absence of measurable electrical potential across the membrane. Addition of valinomycin induces a membrane potential of approximately 50 mV (interior negative) as estimated by uptake of the lipophilic cation triphenylmethylphosphonium, but has surprisingly little effect on 5-hydroxytryptamine transport. Addition of 2,4-dinitrophenol dissipates the valinomycin-induced membrane potential. In the absence of valinomycin, 2,4-dinitrophenol has no effect on 5-hydroxytryptamine transport but valinomycin and 2,4-dinitrophenol together inhibit transport, probably by dissipation of the K+ gradient. These results are consistent with an electroneutral mechanism in which 5-hydroxytryptamine influx is directly coupled to potassium ion efflux and argue against an electrogenic mechanism in which there is a net influx of positive charge with 5-hydroxytryptamine.
mesh_terms: D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D001792:Blood Platelets / Q000378:metabolism*; D004140:Dinitrophenols / Q000494:pharmacology; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects; D009861:Onium Compounds / Q000097:blood; D011188:Potassium / Q000494:pharmacology*; D012701:Serotonin / Q000097:blood*; D013552:Swine; D014320:Triphenylmethyl Compounds / Q000097:blood; D014634:Valinomycin / Q000494:pharmacology
chemical_list: D004140:Dinitrophenols; D009861:Onium Compounds; D014320:Triphenylmethyl Compounds; C011561:triphenylmethylphosphonium; D014634:Valinomycin; D012701:Serotonin; D011188:Potassium