Stimulation of the active transport of serotonin into mouse platelets by the sulfhydryl oxidizing agent diamide

Abstract

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.

The membrane‐bound rat serotonin transporter, SERT1, is an oligomeric protein

“…Previous studies have shown that disulfides are critical determinants of serotonin transporter function. Disulfide oxidation has been reported to stimulate serotonin transport in mouse platelets [17], whereas reduction increases the affinity for imipramine, a potent serotonin uptake inhibitor [18]. These observations may indicate that the binding affinity of SERT1 is altered upon oligomerization.…”

Multiplex single-cell analysis of serotonergic neuron function in planarians reveals widespread effects in diverse cell types

“…A key gene significantly differentially Genes differentially expressed in tph+ neurons of lhx1/5-1(RNAi) animals were enriched in GO terms related to tryptophan metabolic process, response to diamide and presynaptic organisation (Figure 4B, Supplementary File 8). Notably, there is evidence concerning the influence of diamide, a sulfhydryl oxidising agent, on serotonin (5-HT) transport [55]. In particular, diamide simulates 5-HT transport in a concentration-dependent manner, with fluoxetine -a selective inhibitor of serotonin reuptake -constraining this effect [55].…”

“…Notably, there is evidence concerning the influence of diamide, a sulfhydryl oxidising agent, on serotonin (5-HT) transport [55]. In particular, diamide simulates 5-HT transport in a concentration-dependent manner, with fluoxetine – a selective inhibitor of serotonin reuptake – constraining this effect [55]. A key gene significantly differentially regulated in this analysis was the serotonin synthesis rate-limiting enzyme tph (h1SMcG0000075, Supplementary File 7).…”