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The present study examines comparatively the effects of theophylline and its metabolites, 1-methylxanthine (1-MX), 3-methylxanthine (3-MX), 1,3-dimethyluric acid (1,3-DMU) and 1-methyluric acid (1-MU) along the rabbit intestine, and explores the underlying mechanism(s). In the small intestine, theophylline produces atropine- and hexamethonium-sensitive increases in both the amplitude of phasic contractions and the basal tone. All metabolites mimic the theophylline's stimulating effect. In particular, concerning the phasic contractions, all metabolites are more potent than theophylline in the duodenum and jejunum, while in the ileum, only 1-MU is more potent. Regarding the basal tone, the metabolites show, in most cases, higher efficacy in all small intestinal regions, the maximum effects of 3-MX and 1-MU on the duodenum and ileum being double or triple the one of theophylline. In the ascending colon, while lower concentrations of theophylline produce an atropine- and hexamethonium-sensitive increase in the basal tone, higher ones produce a postsynaptic, nonadrenergic noncholinergic (NANC) relaxing effect. 1-MU mimics, in a weaker manner, theophylline's effect, while the other metabolites produce only relaxation, the potency rank of order being 3-MX>1-MX=1,3-DMU>theophylline. It is suggested that the theophylline and its metabolites stimulatory effect involves a cholinergic pathway, while the relaxing one is due to 3′,5′-cyclic adenosine monophosphate (cAMP) elevation mediated by the theophylline and its metabolites inhibitory action on phosphodiesterases (PDEs). [ABSTRACT FROM AUTHOR]

Background and aims: The gastroprokinetic activities of ghrelin, the natural ligand of the growth hormone secretagogue receptor (GHS-R), prompted us to compare the effect of ghrelin with that of synthetic peptide (growth hormone releasing peptide 6 (GHRP-6)) and non-peptide (capromorelin) GNS-R agonists both in vivo and in vitro. Methods: In vivo, the dose dependent effects (1-150 nmol/kg) of ghrelin, GHRP-6, and capromorelin on gastric emplying were measured by the 14C octanoic breath test which was adapted for use in mice. The effect of atropine, NG-nitro-L-arginine methyl ester hydrochloride (L-NAME), or D-Lys³-GHRP-6 (GHS-R antagonist) on the gastroprokinetic effect of capromorelin was also investigated. In vitro, the effect of the GHS-R agonists (1 μM) on electrical field stimulation (EFS) induced responses was studied in fundic strips in the absence and presence of L-NAME. Results: Ghrelin, GHRP-6, and capromorelin accelerated gastric emptying in an equipotent manner, with bell-shaped dose-response relationships. In the presence of atropine or L-NAME, which delayed gastric emplying, capromorelin failed to accelerate gastric emptying. D-Lys³-GHRP-6 also delayed gastric emptying but did not effectively block the action of the GHS-R ogonists, but this may be related to interactions with other receptors. EFS of fundic strips caused frequency dependent relaxations that were not modified by the GHS-R agonists. L-NAME turned EFS induced relaxations into cholinergic contractions that were enhanced by ghrelin, GHRP-6, and capromorelin. I Conclusion: The 14C octanoic breath test is a valuable technique to evaluate drug induced effects on gastric emptying in mice. Peptide and non-peptide GHS-R agonists accelerate gastric emptying of solids in an equipotent manner through activation of GHS receptors, possibly located on local cholinergic enteric nerves. [ABSTRACT FROM AUTHOR]

A plasma motilin peak and a partial gallbladder emptying precede the antral phase III of the migrating motor complex (MMC). To clarify the causal relationship between these factors, we aimed to study the role of motilin in interdigestive gastrointestinal and gallbladder motility simultaneously. In addition, involvement of 5HT3 receptors in the action of motilin was studied. Eight fasting, healthy male volunteers received 13 Leu-motilin or 0.9% NaCl i.v. for 30 min, in randomized order on two separate occasions, from 30 min after phase III. Seven of the eight subjects also received the 5HT3 receptor antagonist ondansetron in addition to motilin, on a third occasion. Antroduodenal motility, gallbladder volumes and plasma motilin were measured. The interval between the start of infusion and phase III was 95.0 (57.6–155.7) min for saline, 28.7 (21.0–33.2) min for motilin, and 39.3 (30.7–100.5) min for motilin + ondansetron (P < 0.05). Gallbladder volume decreased by one-third from 10 min after both motilin and motilin + ondansetron infusion (P < 0.05), and returned to baseline with duodenal passage of phase III. In two of the seven subjects phase III was absent after motilin + ondansetron, although gallbladder volume decreased and only refilled during a later spontaneous phase III. We conclude that motilin induces both partial gallbladder emptying and antral phase III. Indeed, although gallbladder emptying clearly precedes antral phase III, ondansetron only prevented phase III in some cases and had no effect on gallbladder emptying. Passage of phase III in the duodenum makes an important contribution to gallbladder refilling. [ABSTRACT FROM AUTHOR]

Background/Aims: The enterohepatic circulation of bile acids is related to normal inter-digestive gastrointestinal motility, with the gut peptide motilin also being involved. This study aimed to investigate the effect of intraduodenal artificial bile infusion on antroduodenal and gallbladder motility so as to further elucidate the controlling factors. Methods: Twelve fasting, healthy male volunteers received artificial bile (80 mol% bile acids; 15 mol% phospholipids; 5 mol% cholesterol) or placebo (saline) intraduodenally for 10 min starting 30 min after the end of phase III, according to a double-blind, randomised, cross-over design. Antroduodenal motility, gallbladder volumes, and plasma motilin levels were measured. All values are means ± SEM. Results: The interval between infusion and the subsequent phase III, as well as the origin of this phase III were not significantly different between bile and saline. Antral pressure waves were significantly more frequent during and immediately after bile infusion compared with saline infusion (p < 0.05). The duration of phase I following infusion was significantly longer after bile (24.8 ± 3.7 min) than after saline infusion (13.1 ± 1.7 min; p < 0.05). The mean gallbladder volume tended to increase in the hours following bile infusion, but to decrease after saline infusion (p = 0.06). Plasma motilin increased after bile and saline infusion in an almost identical way. Conclusion: This study provides no clear evidence for a role of intraduodenal artificial bile (i.e. its main constituents) in the regulation of migrating motor complex cycling or feedback inhibition of inter-digestive gallbladder emptying.Copyright © 2001 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Motilin has excitatory effects on the colon of the rabbit and the dog, but little is known of its effect on the human colon. The aim of this study was to investigate the effects induced by motilin and erythromycin A (EMA) on muscle strips and on single cells from primary cultures from human colon. Isotonic contraction was recorded in circular muscle strips from macroscopically normal resection specimens of patients operated on for colonic neoplasm. Agonist-induced intracellular Ca2+ ([Ca2+]i) signalling was studied in primary cultures of colonic smooth-muscle cells using the ratiometric Ca2+ indicator Indo 1, on a laser-scanning confocal epifluorescence microscope. In circular muscle strips, norleucine13-porcine motilin ([Nle13]-pm)and EMA induced tonic contractions with an EC50 of 92 ± 21 nmol L-1 and 31 ± 16 μmol L-1, respectively. The maximal contraction was 21 ± 4% (motilin) and 33 ± 12% (EMA) of the response to 10-4 mol L-1 acetylcholine (ACh). The motilin antagonist OHM-11526 (10-5.5 mol L-1) abolished the effects of both [Nle13]-pm and EMA. Neither tetrodotoxin (10-5.5 mol L-1), L-nitro-D-arginine methyl ester (L-NAME) (10-3.5 mol L-1) nor guanethidine (10-5 mol L-1) interfered with the effects of [Nle13]-pm or EMA. [Nle13]-pm (10-11-10-6 mol L-1) induced rises of [Ca2+]i in cultured colonic myocytes. At 10-6 mol L-1, 94% of the cells responded, and half of the cells responded at 1.4 nmol L-1 [Nle13]-pm. 81% (35/43) and 95% (75/79) responded to EMA (10-6 mol L-1) and acetylcholine (ACh, 10-4 mol L-1), respectively. The motilin antagonist GM-109 inhibited motilin- and EMA-induced [Ca2+]i rises. In the absence of extracellular Ca2+, only 13% (7/52) of the cells responded to [Nle13]-pm (10-6 mol L-1) vs. 90% (47/52) to ACh (10-4 mol L-1). Motilin and EMA have direct excitatory effects on circular smooth muscle from the human colon and these effects are mediated via a smooth-muscle motilin receptor. These findings suggest that motilin may regulate colonic motility and that motilides may have therapeutic potential for the treatment of colonic hypomotility. [ABSTRACT FROM AUTHOR]

Subcutaneous octreotide (Sandostatin) injections lead to gall stone formation in 13-50% of acromegaly patients during one year of therapy. This study explored the effects of octreotide on interdigestive gall bladder emptying, antroduodenal motility, and motilin release. Ambulatory antroduodenal manometry was performed in six acromegaly patients before and after two months of octreotide therapy (100 micrograms thrice daily, subcutaneously). Ultrasonographic gall bladder volume measurements and plasma motilin concentrations were obtained during two migrating motor complex (MMC) cycles. Before octreotide treatment, nine of 26 phase III activities started in the antrum and 17 of 26 in the duodenum whereas during treatment 47 of 48 of phase III activity started in the duodenum (p < 0.05). Before treatment, interdigestive gall bladder emptying (mean (SEM) 39.9 (4.0)% of maximal fasting volume) and plasma motilin peaks preceded antral phase III but not duodenal phase III. During octreotide therapy no significant motilin fluctuation or gall bladder emptying was seen. Fasting gall bladder volume increased from 40.9 (9.1) ml before to 68.0 (14.8) ml (p < 0.05) during octreotide treatment. In conclusion, two months' treatment with octreotide increases the number of duodenal phase III like activity and virtually abolishes antral phase III, plasma motilin peaks, and interdigestive gall bladder emptying. These effects might contribute to the high risk of gall stone formation during longterm octreotide treatment. [ABSTRACT FROM PUBLISHER]

In primary anorexia nervosa, gastric motility is often impaired and ensuing symptoms further discourage eating. Prokinetic agents have been shown to accelerate gastric emptying in affected patients. This study investigated whether emptying of a radiolabelled semisolid 1168 kJ meal and antral contractility were enhanced by intravenous erythromycin. Eight women and two men with anorexia nervosa (21-46 years, 50-75% of ideal body weight) received 200 mg erythromycin or placebo under crossover double blind conditions. Gastric emptying and antral contractility were recorded scintigraphically for 90 minutes. In addition, plasma motilin and pancreatic polypeptide concentrations were determined. With placebo, antral contractions were of regular 3 cycles/minute frequency. With erythromycin, less frequent and partly arrhythmic long duration contractions set in and emptying was accelerated: after 90 minutes, the activity remaining in the stomach was markedly less than with placebo in all patients (Sign test, p < 0.002). Basal motilin and pancreatic polypeptide concentrations were normal and showed a normal response to the meal in all patients. Motilin concentrations decreased slightly more and pancreatic polypeptide concentrations increased markedly more with erythromycin than with placebo, possibly because the meal reached the intestine earlier. In conclusion, erythromycin accelerated emptying markedly and in most patients induced an antral motor activity characterised by long duration contractions occurring at often irregular intervals. [ABSTRACT FROM PUBLISHER]

Plasma samples from 21 patients with small cell carcinoma of the lung were screened for pancreatic polypeptide, somatostatin, motilin, and vasoactive intestinal polypeptide. One patient had severe impairment of both renal and liver function. In the 20 remaining subjects vasoactive intestinal polypeptide concentrations were normal, and only two patients had increased concentrations of somatostatin. Increases in pancreatic polypeptide were detected more commonly (7/20), but these may have been non-specific age related increases. The major finding was high concentrations of motilin (greater than 496 pg/ml) in 17 of 20 patients. Plasma motilin was subsequently assayed in 16 more patients with lung cancer, including 10 patients with non-small cell carcinoma of the lung. At concentrations over 900 pg/ml plasma motilin appears to be a tumour marker for small cell carcinoma of the lung with acceptable sensitivity (59%) and specificity (78%). The origin of increased plasma motilin in small cell carcinoma of the lung was investigated. Bombesin (gastrin releasing peptide), a peptide known to stimulate the release of motilin in man, was, as in previous studies, detected in tumour but not in plasma, except in one patient out of 21. Immunohistochemical studies failed to detect motilin antigen in biopsy samples. Motilin tumour content was found to be low in tumour tissue from three patients with small cell carcinoma of the lung who had appreciable hypermotilinaemia and from three patients with non-small cell carcinoma of the lung who had either normal or slightly raised plasma motilin concentrations. The stimulus to motilin secretion in patients with small cell carcinoma of the lung remains unclear. [ABSTRACT FROM PUBLISHER]

Serum lysozyme levels were determined in healthy volunteers, patients with Crohn's disease, and patients with ulcerative colitis. The mean concentration in Crohn's disease was significantly greater than in the other groups. In patients with Crohn's disease, as well as in patients with ulcerative colitis, the lysozyme levels correlated with the severity of the disease process and with the extent of the lesions: the more severe the disease and the more extensive the involvement, the higher the lysozyme levels. However, the lysozyme values of the different groups overlapped considerably. Our results indicate that lysozyme determinations have only limited discriminative value for the diagnosis of Crohn's disease and for determining the severity and the extent of the disease process in the individual patient. [ABSTRACT FROM PUBLISHER]

The article explores the potential of motilin and ghrelin receptors as targets for prokinetic drugs. It recalls the discovery of the relation between motilin and migrating motor complex (MMC). It mentions that desensitization of the motilin receptor has been invoked as a possible reason for the failure of motilin agonists during prolonged treatment. It notes that the absence of the MMC was originally linked to bacterial overgrowth, which is believed to play a role in the development of irritable bowel syndrome (IBS).