Effect of alpha-trinositol on secretion induced by Escherichia coli ST-toxin in rat jejunum.

AIM: d-myo-inositol-1,2,6-trisphosphate (alpha-trinositol, PP56), is a synthetic isomer of the intracellular second messenger, d-myo-inositol-1,4,5-trisphospahate. The pharmacological actions of alpha-trinositol include potent anti-inflammatory properties and inhibition of the secretion induced by cholera toxin and obstructive ileus. In the present study, we investigated whether alpha-trinositol was able to influence the secretion induced by heat-stable ST-toxin from Escherichia coli in the rat jejunum. METHODS: A midline abdominal incision was performed in anaesthetized male Sprague-Dawley rats and a 6-7 cm long jejunal segment was isolated with intact vascular supply and placed in a chamber suspended from a force displacement transducer connected to a Grass(R) polygraph. Intestinal net fluid transport was continuously monitored gravimetrically. Crystalline ST-toxin (120 mouse units) was introduced into the intestinal lumen and left there for the rest of the experiment. When a stable secretion was observed, alpha-trinositol (60 mg kg-1 h-1) or saline were infused during 2 h, followed by a 2-h control period. RESULTS: alpha-Trinositol induced a significant (P < 0.001) inhibition of ST-toxin secretion within 30 min, lasting until 2 h after infusion had stopped. The agent also moderately increased (P < 0.05) net fluid absorption in normal jejunum. Mean arterial pressure (P < 0.001) and heart rate (P < 0.001) were reduced by alpha-trinositol. CONCLUSION: The inhibition by alpha-trinositol of ST-toxin induced intestinal secretion is primarily secondary to inhibition of secretory mechanisms and only to lesser extent due to increased absorption. The detailed mechanisms of action have not been clarified but may involve suppression of inflammation possibly by means of cellular signal transduction.

Effect of inositol-trisphosphate on fluid transport and protein extravasation in the obstructed small bowel.

BACKGROUND: Small-bowel obstruction is characterized by accumulation of fluid in the obstructed intestine. A pronounced inflammation in the obstructed gut wall has been shown to play an important role in the pathogenesis of the profuse fluid losses. alpha-Trinositol (D-myo-inositol-1,2,6-trisphosphate; PP56) has potent anti-inflammatory as well as antisecretory properties. The effects of alpha-Trinositol on inflammation and fluid losses in the obstructed small intestine are examined. METHODS: A total obstruction of the proximal part of the rat jejunum was induced during 18 h by thread ligation. A small segment of the obstructed intestine, with intact vascular and nervous supply, was placed in a chamber suspended from a force displacement transducer allowing for continuous registration of net fluid transport on a Grass polygraph. Three groups were included. One group (n = 12) received low-dose alpha-Trinositol (bolus: 2 mg kg(-1); IV infusion: 10 mg kg(-1) min(-1)), a second group (n = 10) received high-dose alpha-Trinositol (bolus: 12 mg kg(-1); IV infusion: 60 mg kg(-1) min(-1)), while a control group (n = 9) received corresponding volumes of isotonic saline (bolus: 0.5 ml; IV infusions 15 microl min(-1)). Quantitative measurement of extra-vasated Evans blue albumin in the obstructed jejunum was used as a marker of inflammation. RESULTS: High-dose alpha-Trinositol induced a significant (P < 0.001) inhibition of net fluid secretion, while low-dose alpha-Trinositol had no significant effect versus saline. In contrast, both doses of alpha-Trinositol induced significant inhibition of EB-albumin leakage (P < 0.05). CONCLUSION: High-dose alpha-Trinositol is a potent inhibitor of fluid secretion in obstructive ileus, most probably involving an anti-inflammatory mechanism.