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.