Motility changes induced by intraluminal FeSO4 in guinea pig jejunum.

BACKGROUND: Dietary iron supplementation is associated with gastrointestinal (GI) side effects including vomiting, nausea, and diarrhea. Although inorganic iron in high concentrations may be damaging to the intestinal mucosa, we hypothesize that there are physiological effects on the GI tract that occur at concentrations achieved by supplementation. Thus, our aim was to investigate the effect of intraluminal ferrous sulfate (FeSO4 ) on jejunal motility. METHODS: Segments of guinea pig jejunum were cannulated and the intraluminal pressure recorded with a transducer, while movements were recorded with a video camera. Peristaltic threshold was the oral pressure that evoked four consecutive propulsive contractions. The nutrients decanoic acid (1 mM), l-phenylalanine (50 mM), or the micronutrient FeSO4 (1 mM) were infused intraluminally. We also tested the effect of FeSO4 on electrochemically detected serotonin (5-HT, 5-hydroxytryptamine) released from in vitro tissues, both at rest and following mechanical stimulation. KEY RESULTS: The jejuna peristaltic threshold was significantly decreased by all three nutrients: FeSO4 : 31 ± 2-23 ± 3 mmH2 O; decanoic acid: 27 ± 2-14 ± 2 mmH2 O; and l-phenylalanine: 30 ± 3-14 ± 3mmH2 O. Of the three, only decanoic acid induced segmentation, while FeSO4 inhibited decanoic acid-induced segmentation. Resting 5-HT release was increased by FeSO4 (128% of control), but mechanically evoked 5-HT release was reduced (70% of control). CONCLUSIONS & INFERENCES: These data suggest that some luminal effects of inorganic iron on jejunal motility could be mediated through a pathway involving altered release of 5-HT. A better understanding of the interaction between luminal iron and 5-HT containing enterochromaffin cells could improve iron supplementation strategies, thus reducing side effects.

Simultaneous measurement of serotonin and melatonin from the intestine of old mice: the effects of daily melatonin supplementation.

Ageing is associated with important changes in gastrointestinal function and in the levels of intestinal hormones secreted. Enterochromaffin (EC) cells containing serotonin (5-HT) and melatonin may play a major role in maintaining gut function during ageing. Our aim was to characterise the mucosal availability of 5-HT and melatonin in the ileum and colon of a mouse model of ageing. Female young mice (2-5 month; n = 6), aged mice (22-24 months; n = 6) and aged mice treated with melatonin (n = 6; 10 mg/kg/day) were examined. Electrochemical methods were used to measure 5-HT and melatonin concentrations near the mucosal surface of ileum and distal colon. Amperometry studies showed that steady state levels of 5-HT from ileum and colon were decreased in aged mice treated with melatonin when compared to aged mice, while compression-evoked 5-HT release was unchanged. Differential pulse voltammetry studies showed that young mice had concentrations of 5-HT of 4.8 +/- 0.8 mum in the ileum and 4.9 +/- 1.0 mum in the colon. Concentrations of melatonin were 5.7 +/- 1.4 mum in the ileum and 5.6 +/- 1.9 mum in the colon. Compared to young mice, the levels of 5-HT and melatonin were increased in aged mice (combined ileum and colon: 5-HT = 130% and melatonin = 126% of young mice) and decreased in melatonin-treated mice (5-HT = 94% and melatonin = 82%). In conclusion, our data show that the availability of gut 5-HT and melatonin is increased in aged mice and melatonin treatment suppresses natural gastrointestinal production of 5-HT and melatonin in the aged mouse intestine.