EFFECTS OF SEX STEROIDS ON SEROTONIN UPTAKE IN BLOOD PLATELETS

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Abstract
Blood platelets were suggested as a model for serotonin uptake and storage in the brain. To examine possible effects of sex steroids, platelets from human volunteers were incubated for 15 min with estradiol, testosterone and dihydrotestosterone, and then incubated for 1 min with radioactive serotonin. The effects of the various steroids on serotonin uptake were measured. At 10-3 M, estradiol decreased serotonin uptake by 70%, testosterone by 49%, and dihydrotestosterone by 25%. Both estradiol and testosterone showed maximal enhancement of uptake at 10-6 M; estradiol increased serotonin uptake by 41%, and testosterone by 60%. Dihydrotestosterone maximally facilitated uptake by 40% at a concentration of 10-4 M. No sex differences were found in either direction or in magnitude of change in uptake due to any hormone. The effects of estradiol may be of physiological significance and the site of action of the steroid effect on serotonin uptake may be the cell membrane of the platelets.