摘要:

Abstract.Reflex activation of the enteric nervous system (ENS) from the intestinal lumen and also from the serosa induces intestinal secretion. Thus mechanical distention, cholera toxin, heat‐stable enterotoxin fromE. coli, bile acids, mucosal inflammation and chemical peritonitis all induce an intestinal secretion that is inhibited by 60–100% by nerve‐blocking agents. As a result of a large number ofin vitroandin vivostudies, a picture of the organization of the secretory enteric nervous reflexes is now emerging. In secretory states with preserved intact intestinal epithelium, it is proposed that the reflex activation occurs via stimulation of receptor cells, i.e. epithelial endocrine cells such as EC and N‐cells, which release peptides/amines into the interstitial space and thereby activate nerves close to the epithelium. The afferent neurones appear to transfer the reflex to the myenteric plexus, probably by using tachykinins as transmitters. This is in agreement with a superior and co‐ordinating role for the myenteric plexus in the control of intestinal function by the ENS. Interneurones in turn mediate the transmission of the nerve signal to the submucosal plexus and the efferent neurones via cholinergic, nicotinic postganglionic receptors. The transmitters at the effector cells are acetylcholine and pro

ISSN:0954-6820    

DOI:10.1111/j.1365-2796.1990.tb01484.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Abstract.Vasoactive intestinal peptide (VIP) is a potent stimulant of duodenal HCO3−secretion and may, like prostaglandins, have a stimulatory role in the local duodenal HCO3−response to luminal HCl. Using a proximal duodenal loop in conscious rats, we examined the local luminal release of HCO3−. VIP and prostaglandin (PG) E2in response to increasing concentrations of HCl (0.01–150 mmol l−1), perfused for 5 min at 60‐min intervals. HCO3−and PGE2were detected in all basal saline perfusate effluents, and were increased in a concentration‐dependent manner by all acid concentrations tested. VIP was increased in a concentration dependent manner from pH 3. Exogenous VIP did not affect the basal luminal output of PGE2, or vice versa. Inhibition of prostaglandin synthesis by indomethacin augmented the HCl‐stimulated luminal release of VIP, as well as the HCO3−response to exogenous VIP. The results are in agreement with previous studies, demonstrating that PGE2is an important regulator of the duodenal HCO3−response to HCl in the rat. In addition, prostaglandins may negatively modulate the release of VIP from local VIPergic neurones, as well as the HCO3−secretagogue effect of VIP. Released VIP may contribute to the

ISSN:0954-6820    

DOI:10.1111/j.1365-2796.1990.tb01485.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Abstract.Eicosanoids have been shown to be important modulators of intestinal secretion. In cholera, cAMP is often regarded as the sole mediator, but recent data suggest that 5‐hydroxytryptamine (5‐HT) and prostaglandin (PG) E2also play important roles. Thus cholera toxin (CT) increases their release from the rat jejunumin vivo, and human cholera is associated with an increased luminal ‘overflow’ of PGE2.In vitroevidence of secretion can be obtained with PG concentrations 100‐ to 1000‐fold lower than those required for activation of the adenylate cyclase. Furthermore, 5‐HT induces secretion associated with increased ‘overflow’ of PGE2, but without a change in mucosal cAMP. CT‐induced release of PGE2and fluid secretion can be decreased by indomethacin or by the 5‐HT2‐receptor antagonist, ketanserin, whereas the release of 5‐HT and cAMP is not affected by either substance. Secretion caused by vasoactive intestinal polypeptide (VIP) is associated with increased mucosal cAMP levels, without a change in PGE2release, and is unaffected by indomethacin and ketanserin. These results suggest that CT stimulates the release of 5‐HT, which in turn causes the release of PGE2. The latter substances probably act via a local intramural reflex and contribute to secretion by mechanisms t

ISSN:0954-6820    

DOI:10.1111/j.1365-2796.1990.tb01486.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Abstract.The intestinal mucosa is composed of multiple barriers to the lumen‐to‐blood transport of solutes, including the unstirred water and mucous layers, the apical and basolateral cell membranes of the epithelial cell, the paracellular junctions, the interstitial matrix, and the capillary and lymphatic endothelia. The epithelial barrier appears effectively to restrict the movement of solutes with a radius as low as 3 Å, yet it also permits limited permeation by molecules as large as albumin (36 Å radius). There is evidence to suggest that the restrictive properties of the gastrointestinal mucosa are significantly altered under various physiological and pathological conditions, and measurement of plasma (or luminal) clearances of water‐soluble molecules has proved to be a popular method for studying intestinal permeability. The aim of this review is to discuss the concept of the plasma clearance method, methodological aspects of the technique, factors that influence plasma‐to‐lumen clearance measurements (e.g. solute size, blood flow, and permeability of the epithelial cell barrier), and advantages and disadvantages of the clearance method. Finally, application of the clearance technique to the study of ischaemia/reperfusion‐, ethanol‐, and FMLP‐induced mucosal injury

ISSN:0954-6820    

DOI:10.1111/j.1365-2796.1990.tb01487.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Abstract.This paper reviews the scientific background to the development of new drugs for the treatment of diarrhoeal diseases, and it includes an update of three classes of drugs which may prove useful; gut specific α2‐adrenergic agonists, intestinal Cl−channel blockers, and somatostatin analo

ISSN:0954-6820    

DOI:10.1111/j.1365-2796.1990.tb01488.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY