Uptake of dopamine by platelets in vivo.

Circulating platelets of cats infused with (14)C-dopamine take up the amine against a concentration gradient, with maximal concentration occurring 10 min after infusion. 58%, of the platelet-bound radioactive dopamine was localized in a subcellular fraction rich in 5-hydroxytryptamine (5-HT) storage organelles. The results support earlier work with human platelets showing in vitro dopamine uptake by normal platelets, and in vivo accumulation in parkinsonian patients treated with L-dopa.