Role of 5-hydroxytryptamine (serotonin) in oral glucose intolerance.
The aim of the present study was to investigate the metabolic base of psychoneurological symptoms, most notably tiredness and loss of concentration ability, appearing after carbohydrate-rich meals and during oral glucose tolerance tests. Such metabolic changes may be the cause of many accidents attributed to the "human factor". Oral glucose tolerance tests (OGTT) were performed in healthy volunteers, divided into symptomatic (n = 21) and symptom-free (n = 15) groups. Since the symptoms arising during OGTT simulate those in alcohol intoxication, a method for clinical examination of alcohol intoxication was used to separate symptom-free from symptomatic subjects. Comparison of blood glucose concentrations during OGTT revealed the symptomatic group to have higher concentrations in blood samples taken 15 min (p less than 0.05), 30 min (p less than 0.01), 45, 60 and 90 min (p less than 0.05) after intake of glucose than those having no symptoms. The symptoms began when the glucose concentration was at maximum, some 38 min (mean value) following the ingestion of glucose. The symptomatic subjects demonstrated a normal assimilation rate of glucose (mean 1.7 %/min) as tested with intravenous glucose tolerance tests and the differences in blood glucose concentrations between the groups is concluded to depend on the rate of absorption of glucose from the intestinal tract. The enterochromaffine cells of the intestinal tract are the site of biosynthesis, storage and release of 5-hydroxytryptamine (5-HT) (serotonin). In whole blood practically all of the 5-HT is of thrombocytic origin. Thrombocytes are thought to be peripheral models of 5-HT neurons in regard to 5-HT uptake, storage release and metabolism. Thrombocytes have a mechanism for 5-HT uptake analogous to the reuptake mechanism for 5-HT in the serotonergic nerve terminals. The whole blood 5-HT changes parallel changes in the 5-HT concentrations of the neurons. In this work 5-HT concentrations were measured during OGTT in whole blood to ascertain the possible relation between 5-HT changes and glucose absorption. For this purpose a reliable, fluorometric method for 5-HT was developed with the following improvements: In whole EDTA-blood the oxidation of 5-HT was prevented with ascorbic acid. The oxidation of hemoglobin iron to ferri-iron was prevented with carbon monoxide, because 5-HT, being a phenol, will otherwise form a complex with ferri-iron. Proteins were precipitated with perchloric acid and the supernatant neutralized before purification of 5-HT by cation exchange.(ABSTRACT TRUNCATED AT 400 WORDS)
D000328:Adult; D000818:Animals; D005221:Fatigue; D005260:Female; D005947:Glucose / Q000378:metabolism; D005951:Glucose Tolerance Test; D006801:Humans; D007003:Hypoglycemia / Q000097:blood* / Q000175:diagnosis; D007408:Intestinal Absorption; D007413:Intestinal Mucosa / Q000378:metabolism; D008297:Male; D009043:Motor Activity; D011581:Psychological Tests; D011602:Psychophysiologic Disorders / Q000097:blood* / Q000175:diagnosis / Q000209:etiology; D012701:Serotonin / Q000097:blood* / Q000378:metabolism; D013552:Swine; D014787:Vision Tests
D012701:Serotonin; D005947:Glucose