Disseminated rectal carcinoid tumor with production of immunoreactive motilin.

This report presents a patient with a rectal carcinoid tumor of small size ( 14 mm in diameter), with typical growth pattern, localized in the mucosa. Despite these microscopically good prognostic features the patient died from metastatic disease 30 months later. The tumor had an unusual hormone profile with main secretion of immunoreactive motilin and serotonin.

Transport of serotonin from the rat jejunal lumen into mesenteric veins in vivo.

The transport of labelled (hot) and non-labelled (cold) serotonin (5-HT) into the mesenteric venous circulation was studied after instillation of test solutions into an isolated jejunal loop of anaesthetized rats. After instillation of [3H]H2O and [14C]5-HT there was an almost parallel appearance of the isotopes in mesenteric venous blood. After instillation of 5-HT a marked early increase of the total amounts of cold 5-HT was observed in mesenteric veins compared with animals instilled with saline only.

A possible mechanism for the release of serotonin from the gut caused by pentagastrin.

Pentagastrin (PG) is a potent agent causing release of serotonin (5-HT) from patients with carcinoid tumors. The physiological release of 5-HT from gut enterochromaffin cells is controlled by beta-adrenoceptors. Studies on carcinoid tumor cell suspensions, acute or in culture, have shown that catecholamines (CA), but not PG, release 5-HT, thus indicating an indirect mode of action by the peptide.

Vagal release of serotonin into gut lumen and portal circulation via separate control mechanisms.

The mechanisms controlling vagally induced release of serotonin-like immunoreactivity (5-HTLI) into portal circulation and jejunal lumen were studied in individual cats. In control animals, electrical vagal nerve stimulation significantly enhanced both the endoluminal secretion rate of 5-HTLI and the release of 5-HTLI into the portal vein. The vagally induced release of 5-HTLI into portal circulation was blocked by pretreatment with propranolol or phenoxybenzamine, or by previous removal of the superior cervical ganglia, but was not blocked by atropine or hexamethonium.

Vagal release of serotonin into gut lumen and portal circulation via separate control mechanisms.

The mechanisms controlling vagally induced serotonin-like immunoreactivity (5-HTLI) release into portal circulation and jejunal lumen were studied in individual cats. In control animals, electrical vagal nerve stimulation significantly enhanced both the endoluminal secretion rate of 5-HTLI and the release of 5-HTLI to the portal vein. The vagally induced release of 5-HTLI to the portal circulation was blocked by pretreatment with propranolol or phenoxybenzamine, or by prior removal of the superior cervical ganglia, but was not blocked by atropine or hexamethonium.

Regulatory mechanisms in endoluminal release of serotonin and substance P from feline jejunum.

The mechanisms controlling vagally induced 5-HT and SP release into the jejunal lumen were studied in the cat. In control animals, electrical vagal nerve stimulation doubled the rate of endoluminal secretion of 5-HT and SP. Propranolol pretreatment did not alter luminal secretion of these hormones.

Adrenergic control of serotonin release from carcinoid tumor cells in vitro and in vivo.

Serotonin (5-HT)-producing human carcinoid tumors of midgut origin were transplanted to the anterior eye chamber of cyclosporine-treated rats. The release of 5-HT from in oculo transplants was studied after stimulation with adrenoceptor agonists applied locally to the eye. Chamber fluid was collected by micropuncture of the eye.

Studies on the mucosal hyperaemia of the feline small intestine observed at endoluminal perfusion with substance P.

Substance P-like immunoreactivity (SPLI) was found in the luminal contents of the feline small intestine. A physiological role for endoluminal substance P (SP) was explored in in vivo experiments, where feline jejunal segments were endoluminally perfused with saline or a low concentration of SP. A jejunal segment was initially perfused with saline, followed by SP in saline, and finally perfused with saline alone.

Verapamil and diarrhoea in the carcinoid syndrome--clinical and experimental observations on serotonin release.

A patient with the midgut carcinoid syndrome with severe diarrhoea and proven hypersecretion of serotonin (5-HT) was treated with low doses of verapamil perorally. During treatment the patient was completely relieved of diarrhoea but discrete facial flushing persisted during treatment. When treatment was cessated, diarrhoeas recurred.

Regional and selective changes in blood flow of the feline small intestine induced by endoluminal serotonin.

A physiological role for endoluminal serotonin (5-HT) was explored in in vivo experiments, where feline jejunal segments were endoluminally perfused with saline or a low concentration of 5-HT. The upper jejunal segment was initially perfused with saline, followed by 5-HT in saline, and finally perfused with saline alone. The lower jejunal segment served as a control with constant perfusion with saline.

A case of midgut carcinoid with breast metastasis and cellular localization of serotonin and substance P.

A case of midgut carcinoid with breast metastasis is reported. Hepatic metastases stored large amounts of serotonin as demonstrated by the Falck-Hillarp technique. Immunocytochemically serotonin and substance P, which may co-exist in gut enterochromaffin cells, were demonstrated in separate populations of tumor cells both in the hepatic and mammary neoplasms.

The influence of cholinergic and adrenergic blockade on the portal release of substance P in the cat.

The effect of efferent electrical stimulation of the divided thoracic vagus nerves on the release of substance P-like immunoreactivity (SPLI) into the portal vein was studied in anesthetized cats. Under basal conditions portal SPLI levels were fairly constant. During the first 5 min of vagal stimulation there was a significant increase of the portal plasma levels of SPLI.

Adrenergic control of serotonin release from a midgut carcinoid tumour.

A case of recurrent midgut carcinoid tumour with disseminated spread is described, in which the clinical diagnosis was supported by measurements of elevated basal serotonin (5-HT) levels in peripheral blood and increased 5-HT responses to pentagastrin provocation, despite normal urinary levels of 5-hydroxyindoleacetic acid. Preoperative diagnosis was obtained by concomitant determinations of 5-HT in mesenteric and hepatic veins. The carcinoid tumour was studied immunocytochemically using antisera to tyrosine hydroxylase and 5-HT.

On the mode of action of the pentagastrin test in the carcinoid syndrome.

Provocation with pentagastrin (PG) (0.6 micrograms/kg intravenously) causes a release of serotonin (5-hydroxytryptamine (5-HT] in excess of the metabolizing capacity associated with carcinoid symptoms and a moderate fall in systemic arterial blood pressure in patients with midgut carcinoids and hepatic metastases. In this study PG also caused a release of 5-HT into portal circulation of anesthetized cats with stable peripheral levels of 5-HT in whole blood, indicating an effective hepatic metabolization.

The effects of vagal nerve stimulation on endoluminal release of serotonin and substance P into the feline small intestine.

Endoluminal release of serotonin (5-HT), substance P (SP), and motilin was quantitated after thoracic vagal nerve stimulation in the cat. In duodenum and jejunum, simultaneous release of these compounds was observed. In contrast, vagal stimulation did not augment the rate of luminal secretion of either 5-HT or SP in the distal ileum.

The pentagastrin test in the diagnosis of the carcinoid syndrome. Blockade of gastrointestinal symptoms by ketanserin.

The levels of 5-hydroxytryptamine (serotonin, 5-HT) and substance P (SP) were assayed (using high performance liquid chromatography-electron capture and radioimmunoassay methods) in the peripheral blood of 17 patients with known mid-gut carcinoids, 16 of whom had hepatic metastases. All patients had supranormal basal levels of 5-HT and SP. The clinical and hormonal changes induced by two provocation tests, intravenous pentagastrin (PG) and calcium infusion, were compared.

The pentagastrin test in the diagnosis of the carcinoid syndrome.

Serotonin (5-HT) and substance P (SP) were assayed in peripheral blood in patients with known midgut carcinoids and hepatic metastases. All patients had supranormal basal levels of 5-HT and SP. The clinical and hormonal response was evaluated by two provocation tests, pentagastrin (PG) injection or calcium infusion.

Endoluminal substance P as a cause of mucosal hyperemia in the feline gut by a nonneural mechanism.

Exogenous substance P (SP) was perfused into the lumen of the proximal jejunum in 16 fasted cats at a rate of 6.04 +/- 1.96 ng/min.