Platelets and biogenic amines. 1. Platelets are poor investigative models for dopamine re-uptake.
The uptake of 14C-dopamine (DA) by human platelets at 10(-7) -2.5 X 10(-4) M of labelled amine concentration was studied in human platelet-rich plasma. The total uptake could be resolved into two components, one of which was saturable and completely inhibited by 10(-5) imipramine and another which was unsaturable but temperature-dependent. The saturable uptake of DA had an apparent Km of 75 X 10(-6) M and Vmax of 1.34 pmol/10(6) platelets/min. The uptake of unsaturable DA was 1.33 pmol/10(6) platelets/min at 10(-4) M DA. Dopamine exerted a mixed non-competitive inhibition of the saturable 5-HT transport and vice versa. Thus the increase in Km was paralleled by a decrease in Vmax. The low-affinity transport of DA by the human platelets does not share any of the dopamine uptake characteristics found in neuronal tissue. The platelet therefore seems to be a poor model for the presynaptic function of the dopamine neurons.
D001679:Biogenic Amines / Q000097:blood; D001792:Blood Platelets / Q000378:metabolism*; D004298:Dopamine / Q000097:blood*; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D008954:Models, Biological; D012701:Serotonin / Q000097:blood
D001679:Biogenic Amines; D012701:Serotonin; D004298:Dopamine