Alteration of 5-HT uptake by plasma fractions in the premenstrual syndrome

The effects of plasma and an aqueous plasma fraction from patients with premenstrual syndrome (PMS) and control subjects on the uptake of 5-hydroxytryptamine (5-HT) in washed human platelets and rat forebrain synaptosomes were studied. Pre- and postmenstrual samples of unextracted plasma from the control group significantly enhanced platelet uptake of 5-HT. In contrast, an aqueous fraction following extraction of the plasma with organic solvents caused a dose-dependent decrease of 5-HT uptake. Plasma obtained from patients with PMS caused less stimulation of 5-HT uptake compared to plasma from the control group. The aqueous fraction of premenstrual plasma from patients tended to inhibit 5-HT uptake to a greater extent than a similar plasma fraction from controls. The inhibition of 5-HT uptake was associated with an increase in Km. Aqueous plasma fractions from both groups also inhibited 5-HT uptake in brain synaptosomes. However, there were no significant differences between groups. The results of the platelet study suggest that there may be quantitative differences in the plasma concentration of endogenous factors that affect 5-HT uptake between patients with PMS and control subjects and that such differences may explain the previously reported alteration of platelet 5-HT uptake and content associated with PMS symptoms.