title: Abnormalities of 5-hydroxytryptamine uptake and binding by blood platelets from children with Down's syndrome.
abstract: 1. Blood platelets from normal children and children with the trisomy 21 form of Down's syndrome (mongolism) were studied to determine the cause of the well established reduction in platelet 5-HT in the disease.2. Concentrations of endogenous 5-HT in the platelets from mongols were 25.3% of the concentrations found in normal children.3. The net accumulation of 5-HT in the mongol cells was decreased to 52.7% of normal. This reduction was probably due, in part, to a defect in 5-HT transport, because the initial rates of 5-HT uptake at plasma concentrations of 10(-6) and 10(-5)M were significantly slower.4. Experiments on the efflux of 5-HT from mongol platelets loaded with amine showed that the rate of loss was initially 2.6 and later 7.8 times faster than normal.5. Platelet ATP in mongol cells was 26% of normal, and the reduction of ATP and 5-HT was in the molar ratio of 3:1.6. It is considered that the low platelet 5-HT in Down's syndrome is due to a defective 5-HT transport mechanism and impaired 5-HT binding, resulting from a reduction in the essential binding substance, ATP.
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000293:Adolescent; D001665:Binding Sites; D001692:Biological Transport; D001791:Blood Platelet Disorders / Q000378:metabolism*; D001792:Blood Platelets / Q000378:metabolism; D002648:Child; D002675:Child, Preschool; D004314:Down Syndrome / Q000378:metabolism*; D005260:Female; D006801:Humans; D008297:Male; D012701:Serotonin / Q000097:blood / Q000378:metabolism*
chemical_list: D012701:Serotonin; D000255:Adenosine Triphosphate