Stimulation of the active transport of serotonin into mouse platelets by the sulfhydryl oxidizing agent diamide.
The purpose of this study was to determine the effects of diamide, a reversible sulfhydryl oxidizing agent, on the transport of serotonin (5-HT) by mouse platelets. Diamide produced a concentration-dependent (10-200 microM) stimulation of 5-HT transport that was rapid and sustained over 0-10 minutes of incubation. When platelets were incubated with diamide (10-200 microM) in the presence of glucose, the content of reduced glutathione was significantly decreased only at a final concentration of 200 microM, while washed platelets incubated with diamide (10-200 microM), in the absence of glucose, had a significant concentration-dependent decrease in their content of reduced glutathione. Fluoxetine, an inhibitor of the platelet 5-HT transporter, blocked diamide-induced stimulation of 5-HT transport. The kinetics of 5-HT transport showed that diamide caused a marked increase in the maximal rate of transport (Vmax control = 28.4 +/- 1.4 vs. Vmax diamide = 60.9 +/- 4.1 pM/10(8) platelets/4 min) but did not significantly alter the Km values. Ouabain, an inhibitor of platelet Na(+)-K+ ATPase, blocked the stimulation by diamide in a concentration-dependent manner. Dithiothreitol, a disulfide reducing agent, was able to partially reverse the stimulation of platelet 5-HT transport caused by diamide. This study has shown that diamide can stimulate the active transport of 5-HT by mouse platelets and suggests a possible role for free sulfhydryl groups in the regulation of this process.
Bosin
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Pharmacology Section, Indiana University School of Medicine, Bloomington 47405.
Kasper
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D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D001792:Blood Platelets / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D002478:Cells, Cultured; D003958:Diamide / Q000494:pharmacology*; D005978:Glutathione / Q000378:metabolism; D008297:Male; D051379:Mice; D010042:Ouabain / Q000494:pharmacology; D010084:Oxidation-Reduction; D012701:Serotonin / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors / Q000378:metabolism
D003958:Diamide; D012701:Serotonin; D010042:Ouabain; D000254:Sodium-Potassium-Exchanging ATPase; D005978:Glutathione