Comparative effects of growth hormone on water and ion transport in rat jejunum, ileum, and colon.

Specific growth hormone (GH) receptors are located along the entire rat intestine. We have recently shown that GH induces water and ion absorption in the rat ileum. This raises the possibility that GH regulates water and ion transport throughout the intestine. To test this, we have evaluated the effects of GH administration on jejunal, ileal, and colonic water and ion transport, by the in vivo rat perfused intestine, and in vitro, in corresponding segments of intestine mounted in Ussing chambers. In vivo, GH increased water absorption by 250%, 180%, and 80% over baseline in the jejunum, ileum, and colon, respectively. The effect had similar kinetics in the three intestinal regions. In vitro, serosal GH administration induced a decrease in short-circuit current, consistent with an absorptive effect. The effect showed a proximal to distal decreasing pattern. These findings suggest that GH plays a role in the body fluid homeostatic control, promoting water and ion absorption.

Hansenula anomala killer toxin induces secretion and severe acute injury in the rat intestine.

BACKGROUND & AIMS: The yeast Hansenula anomala has been associated with gastrointestinal symptomatology and damage to the intestinal wall in humans. In vitro and in vivo, H. anomala secretes a toxin, killer toxin, which is lethal to other microorganisms. In view of the very high rate of killer phenotype expression recorded for H. anomala strains in nature, this study aimed to investigate the hypothesis that H. anomala killer toxin plays a role in the pathogenesis of H. anomala-induced enteritis. METHODS: Effects of active and heat-inactivated H. anomala killer toxin on intestinal fluid homeostasis and electrolyte balance were investigated in rat small intestine using a standard intestinal perfusion technique. Sections of the perfused jejunum tracts were examined histologically. RESULTS: H. anomala killer toxin induced a significant secretion of water and electrolytes. No significant change was observed when either heat-inactivated H. anomala killer toxin or control growth medium were tested. Histological analysis showed ischemic degeneration of villi and sloughing of surface epithelium in 50% of active H. anomala killer toxin-perfused jejuna. CONCLUSIONS: This paper presents original observations compatible with the hypothesis that H. anomala killer toxin plays a role in the pathogenesis of H. anomala-induced enteritis.

In vivo and in vitro effects of human growth hormone on rat intestinal ion transport.

It has been reported that: 1) ovine growth hormone stimulates intestinal water, sodium, and chloride absorption and 2) specific growth hormone receptors are present in the rat intestine. Aims of this work were to investigate the effects of acute administration of hGH on water and ion transport in the rat ileum in vivo and in vitro. In vivo, the absorption rates of water, sodium, chloride, and potassium were determined in the rat perfused ileum, during a basal period and after i.v. administration of 6 micrograms/kg recombinant DNA-derived hGH. In vitro, electrical parameters were measured before and after the hormone addition to the mucosal or the serosal side of rat ileal mucosa mounted in Ussing chambers. In vivo, growth hormone induced a rapid increase in the absorption rates of water, sodium, chloride, and potassium. In vitro, the serosal, but not the mucosal, addition of growth hormone induced a rapid decrease of transepithelial potential difference and of short-circuit current. The effect was time- and dose-dependent, saturable, but not reversible in the short time. The electrical effect was abolished in the absence of chloride, indicating that it was related, at least in part, to inhibition of basal active chloride secretion. Growth hormone also reduced the short-circuit current increase induced by the secretagogues Escherichia coli heat-stable enterotoxin, theophylline, and calcium ionophore A23187. These results indicate that hGH has a rapid absorptive effect that is related, at least in part, to a direct intestinal antisecretory mechanism. It also reduces active intestinal secretion induced by various secretagogues.

Cholera toxin-induced small intestinal secretion has a secretory effect on the colon of the rat.

BACKGROUND/AIMS: Little information is available on the role of colon during small intestinal secretion. The aim of this study was to examine the effects of secretory changes in the small intestine on the colonic transport of electrolytes and water in vivo. METHODS: The jejunum and colon of the rat were perfused in vivo simultaneously but separately, and jejunal secretion was induced by exposing the jejunum to cholera toxin, 8-bromo-cyclic guanosine monophosphate, or hyperosmolarity. RESULTS: Jejunal perfusion with a hyperosmolar mannitol solution (600 mOsm/L) or with 8-bromo-cyclic guanosine monophosphate (0.5 mmol/L) resulted in net secretion of water in the jejunum but did not affect the baseline rate of water transport in the colon. On the contrary, addition of cholera toxin (1 microgram/loop) to the jejunal segment not only induced a significant local secretory change but also resulted in a similar change in the colon, which was not exposed to cholera toxin. The intestine was transected immediately below the jejunum, thus interrupting the anatomical continuity of the enteric nervous system. This procedure eliminated the distant secretory effect of cholera toxin, thus allowing the conclusion that the enteric nervous system is involved in the distant propagation of the local secretion induced by cholera toxin. CONCLUSIONS: Cholera toxin, but not other secretagogues, triggers a secretory response that is not only local but also extends to distal segments via the enteric nervous system.

Comparative effects of atrial natriuretic peptide and E. coli heat-stable toxin on rat intestinal transport.

Conflicting data have been published in favor of or against a secretory effect of atrial natriuretic peptide (ANP) in the intestine. The reported effects resemble that of Escherichia coli heat-stable enterotoxin (ST). In this work the effects of ANP were studied in well established experimental systems and compared with that of ST. Both peptides induced a prompt secretion of water, Na, and Cl with no effects on K net transport in the in vivo rat perfused jejunum. The addition of ST, but not of ANP, evoked an increase of short circuit current in rat intestinal mucosa mounted in Ussing chambers. ST induced a significant increase in guanylate cyclase activity in intestinal homogenates, whereas ANP showed no effect. No binding sites for ANP were detected in basolateral or brush border membranes, nor in isolated enterocytes by a suction filtration technique. In conclusion, ANP acts as a short-lived intestinal secretagogue in the rat. Its mechanism of action is different from that of E. coli ST and appears to be indirect, since is not mediated by specific intestinal receptors and is not evident in vitro.

[Manometric data collection]. / Il rilievo del dato manometrico.

During the recent years, intraluminal esophageal manometry has developed into an important method for detecting motor function of the esophagus and pharynx. High fidelity instrumentation is now available to perform adequate recording of pressure phenomena of the esophagus. It consists of water-filled catheters systems, perfused by minimally compliant hydraulic system and of intraluminal strain gauge probes. A sleeve catheter assembly is suitable for recording lower sphincteric pressure for long period, despite the respiratory and deglutitive axial movements of the sphincter along the catheter. The pressure events of interest are phasic pressure wave along the esophageal body (usually peristaltic) as well as resting tone and relaxation of upper and lower esophageal sphincters. Recording instrumentation available allows accurate detection of esophageal motor activity both in healthy subjects and in patients.