Influence of calcium or 1,25-dihydroxyvitamin D3 supplementation on the hepatic microsomal and in vivo metabolism of vitamin D3 in vitamin D-depleted rats.

Hypocalcemic vitamin D (D)-depleted rats were supplemented with calcium or 1,25(OH)2D3, and the metabolism of D3 to 25(OH)D3 was studied. Infusion with 7 or 65 pmol 1,25(OH)2D3 X 24 h-1 led to normal or slight hypercalcemia associated with physiological and supraphysiological plasma concentrations of the hormone while calcium supplementation normalized plasma calcium despite 1,25(OH)2D3 concentrations as low as those observed in hypocalcemic controls. Constant administrations of [14C]D3 during the supplementation regimens uncovered a stimulation of the in vivo 25(OH)D3 production by calcium supplementation; this was further confirmed in vitro by an increase in the hepatic microsomal D3-25 hydroxylase. The group supplemented with pharmacological doses of the hormone displayed lower circulating concentrations of both D3 and 25(OH)D3 while the in vitro 25(OH)D3 production remained unaffected by 1,25(OH)2D3. Investigation of the kinetics of intravenous 25(OH)[3H]D3 revealed similar elimination constants in all groups. The data indicate that calcium supplementation of hypocalcemic D-depleted rats results in an increased transformation of D3 into 25(OH)D3 while supplementation with 1,25(OH)2D3 does not affect the in vitro D3-25 hydroxylase but seems to influence the in vivo handling of the vitamin by accelerating its metabolism.

Hepatic handling of vitamin D3 in micronodular cirrhosis: a structure-function study in the rat.

The response to vitamin D3 (D3) was studied in a model of micronodular cirrhosis induced by CCl4. The uptake and C-25 hydroxylation of D3 were then studied in isolated-perfused liver preparations. CCl4-treated rats had a significantly lower fractional hepatic D3 uptake than controls; they also had lower 25-hydroxyvitamin D3 (25(OH)D3) concentrations in both liver and perfusate following 150 min of perfusion. CCl4 induced a wide spectrum of hepatic morphologic changes ranging from mild to large collagen infiltration, but micronodular cirrhosis was present in more than 90% of the animals. Histomorphometric analysis of the liver indicated an overall highly significant increase in the volume density (Vv) of collagen infiltration, and a reduction in the Vv normal hepatocytes following CCl4. Linear relationships were also observed between the Vv normal hepatocytes and the liver, perfusate, and total 25(OH)D3, while the 25(OH)D3 production decreased in a logarithmic fashion as the collagen infiltration of the liver parenchyma increased. These data show that the overall production of 25(OH)D3 is decreased in micronodular cirrhosis; they also indicate, however, that the D3-25 hydroxylase seems to stay unimpaired in the remaining hepatocytes of the diseased liver, and that the Vv normal hepatocytes constitute one of the major determinants of the 25(OH)D3 production by the cirrhotic rat liver.

Abdominal surgery induces Fos immunoreactivity in the rat brain.

Previous neuropharmacological studies indicate that brain peptides are involved in mediating gastric stasis induced by abdominal surgery. Central pathways activated by abdominal surgery were investigated in the rat by using Fos protein as a marker of neuronal activation. Abdominal surgery (laparotomy alone or combined with cecal manipulation) was performed under brief enflurane anesthesia (7-8 minutes), and 1 hour later rats were killed and brains processed for Fos immunoreactivity. Double labeling with Fos and arginine vasopressin, oxytocin, or tyrosine hydroxylase antibodies was also performed. Abdominal surgery induced Fos staining in the nucleus tractus solitarii, paraventricular and supraoptic nuclei of the hypothalamus, locus coeruleus, and ventrolateral medulla. After abdominal surgery, 18-25% of vasopressin and 18-33% of oxytocin-labeled cells were found to be Fos positive in the paraventricular nucleus and 15% of activated cells in the nucleus tractus solitarii were positive for tyrosine hydroxylase immunoreactivity. Enflurane alone induced c-fos expression in the same brain area; however, the number of Fos-positive cells and double-labeled cells were decreased two- to fivefold and three- to eightfold, respectively, compared with the abdominal surgery groups. These data show that abdominal surgery induced activation of specific hypothalamic, pontine, and medullary neurons. These findings may have implications for the understanding of central mechanisms involved in mediating gastric ileus following abdominal surgery.

Estimation of collagen content of liver specimens. Variation among animals and among hepatic lobes in cirrhotic rats.

We undertook a study to evaluate the correlation between morphometric evaluation and colorimetric determination of hepatic collagen content, and to analyze the variation among animals as well as among lobes of the same liver in hepatic collagen content after CCl4-induced micronodular cirrhosis. The results revealed a significant correlation (r = 0.9458; p less than 0.001) between the morphometric and colorimetric methods of collagen evaluation of liver specimens; both methods also significantly distinguished data obtained from controls and from cirrhotic rats (p less than 0.0005). After induction of micronodular cirrhosis by chronic CCl4 administration, a highly significant variation in hepatic collagen content was observed among animals (p less than 0.0001). By contrast, no significant difference in collagen content was observed (p less than 0.05) among hepatic lobes of a given animal. These results indicate that in this animal model of liver cirrhosis, interpretation of biochemical data would benefit by being related to the severity of the hepatic collagen infiltration of each animal. Our data also show that representative values for total hepatic collagen infiltration can be obtained from a single liver specimen; we suggest, however, that the specimen be taken from a major lobe of the liver and that a sufficiently large number of animals be used to avoid occasional sampling errors.

Review article: acid suppression in non-variceal acute upper gastrointestinal bleeding.

Despite a decreased incidence of ulcer disease and improvements in the management of acute upper gastrointestinal (GI) bleeding, mortality remains at about 6-7%. Although endoscopic haemostatic therapy has been demonstrated to be the mainstay of management, the search continues for less invasive medical modalities that might also improve patient outcome. In vitro data have indicated the important role of acid in impairing haemostasis and causing clot digestion. Therefore, theoretically, maintenance of a high intragastric pH (above 6.0) during management of upper GI bleeding is warranted. Until recently, available agents did not permit such a sustained elevation in gastric pH. Early studies with H2-receptor antagonists have not demonstrated significant improvements in important patient outcomes, such as rebleeding, surgery or mortality. With the availability of intravenous formulations of proton pump inhibitors, it is now possible to aim at maintaining gastric pH above 6.0 for 24 h per day. Recent clinical trial data would appear to support the use of proton pump inhibitors to decrease the rate of rebleeding and the need for surgery. This paper provides a review of non-variceal acute GI bleeding, with special reference to the role of proton pump inhibitors in this clinical setting.

Digestive motor effects and vascular actions of CGRP in dog are expressed by different receptor subtypes.

Calcitonin gene-related peptide (CGRP) is a 37 AA peptide localized in blood vessels and nerves of the GI tract. Activation of CGRP receptors (subtypes 1 or 2) usually induces vasodilation and/or muscle relaxation, but its effects in dog and on gastroduodenal motility are still unclear. This study looked for the effect of CGRP and the antagonist CGRP8-37, specific for CGRP type 1 receptor, 1) on GI motility (interdigestive and postprandial), and 2) on hemodynamy, in conscious dogs. During the interdigestive period, the infusion of CGRP1-37 (200 pmol/kg/h) or CGRP8-37 (2000 pmol/kg/h) did not modify the duration of the migrating motor complex nor the release nor the motor action of plasma motilin. The gastric emptying of a solid meal (15 g meat/kg) was reduced by the administration of CGRP1-37 (AUC: 2196 +/- 288.6 versus 3618 +/- 288.4 with saline or T12: 78 +/- 7.3 versus 50 +/- 4.3 min; P < 0.01) and this effect was reversed by the antagonist CGRP8-37. CGRP1-37 significantly (P < 0. 01) diminished arterial pressures (118 +/- 1.6/64 +/- 1.4 vs. 125 +/- 1.4/75 +/- 1.2 mmHg with saline) and accelerated the basal cardiac rhythm (110 +/- 1.4 versus 83 +/- 1.6 beats/min). However, CGRP8-37 failed to block the cardiovascular effects of CGRP1-37. In dog, CGRP could influence digestive motility by slowing the gastric emptying of a meal through an action on CGRP-1 receptors. Hemodynamic effects of CGRP were not blocked by CGRP8-37 and seem therefore mediated by CGRP-2 receptor subtype.

CGRP antagonists and capsaicin on celiac ganglia partly prevent postoperative gastric ileus.

The role of capsaicin-sensitive pathways and CGRP in postoperative gastric ileus was investigated. Abdominal surgery was performed under enflurane anesthesia, and 5 min later, the 20-min rate of gastric emptying was measured by the phenol red method in conscious rats. Surgery inhibited gastric emptying by 76-83% compared with rats receiving anesthesia alone. Capsaicin on the celiac/mesenteric ganglia (10-21 days before) reduced gastric ileus by 33 +/- 8%, whereas perivagal capsaicin had no effect. The IV CGRP-induced inhibition of gastric emptying was completely reversed by the CGRP antagonist, CGRP(8-37) (30 micrograms, IV); CGRP(8-37) (15, 30, or 60 micrograms) or CGRP monoclonal antibody #4901 (2 mg protein) decreased the inhibition of gastric emptying by 11 +/- 7%, 51 +/- 13%, 47 +/- 3%, and 45 +/- 17%, respectively. These results indicate that CGRP and splanchnic capsaicin-sensitive afferents are involved in mediating part of the gastric ileus observed immediately after abdominal surgery.

Intolerance to visceral distension in functional dyspepsia or irritable bowel syndrome: an organ specific defect or a pan intestinal dysregulation?

Functional gastrointestinal disorders (FGID) are characterized by visceral hypersensitivity that could be specific to a region of the gut or reflect a diffuse pan-intestinal disorder. Sensory thresholds to distension at two visceral sites in patients with different FGIDs were determined. According to Rome II criteria, 30 patients from three groups were studied: patients with (i) functional dyspepsia (FD) or (ii) irritable bowel syndrome (IBS), and (iii) patients with concomitant symptoms of FD and IBS. Pain thresholds to balloon distension were determined in stomach and rectum. In FD patients, gastric intolerance to balloon distension was found in 91% patients; rectal hypersensitivity was documented in 18% patients. In IBS patients, rectal hypersensitivity was seen in 75% patients; while gastric hypersensitivity was never found. In patients with concomitant symptoms of FD + IBS, gastric and rectal intolerance to distension were present respectively in 82 and 91% patients. In the whole group, visceral intolerance to distension was documented at one site in 90% patients and at both sites, i.e. stomach and rectum, in 33% patients. Visceral intolerance to distension can be pan-intestinal in patients with multiple sites of symptoms, but appears organ-specific in patients exhibiting a specific site of symptoms.

Effects of the corticotropin-releasing factor (CRF) on rectal afferent nerves in humans.

Corticotropin-releasing factor (CRF) released in the gastrointestinal mucosa from immune cells or enterochromaffin cells may play a role in the modulation of rectal afferent function. In the current study we evaluated the effects of peripherally administered CRF on afferent mechanisms in the human rectum. We used rectal balloon distention in seven healthy volunteers to evaluate the effect of CRF (1 microgram/kg) on visceral afferents originating in the rectum which are involved in the following functions: thresholds and intensity of conscious perception, receptive relaxation, reflex inhibition of internal anal sphincter and a viscerosomatic reflex. Rectal mechanoreceptors were stimulated either by distending the rectum using a volume ramp (40 and 400 mL/min), or by intermittent phasic distention. CRF decreased the thresholds and increased the intensity for the sensation of discomfort in response to both ramp and phasic distention. During slow ramp distention, CRF also lowered the stool threshold. CRF increased rectal compliance during slow ramp distention without affecting the rate of receptive relaxation or the inflection point of the compliance curve. CRF had no effect on viscerosomatic referral patterns, or on the rectoanal inhibitory reflex. These findings are consistent with a dual effect of CRF on afferent pathways mediating perception of aversive rectal sensations, and on rectal smooth muscle.

Delayed gastric emptying induced by inhibitors of nitric oxide synthase in rats.

The effect of the nitric oxide (NO) synthase inhibitor, NG-nitro-L-arginine methyl ester, on gastric emptying of a non-nutrient solution was investigated in conscious rats. NG-Monomethyl-L-arginine (10 mg/kg i.v.) and NG-nitro-L-arginine methyl ester (3 or 10 mg/kg i.v.) inhibited the 20-min rate of gastric emptying of liquids by 34%, 69% and 84% respectively, whereas the 0.3 mg/kg of NG-nitro-L-arginine methyl ester or 3 mg/kg of NG-monomethyl-L-arginine had no effect. The inhibitory effect of NG-nitro-L-arginine methyl ester (3 mg/kg) was prevented by L-arginine (300 mg/kg i.v.), but not by D-arginine (300 mg/kg i.v.). NG-Nitro-L-arginine methyl ester (0.3-10 mg/kg) induced a dose-related increase in mean blood pressure up to 161 +/- 10 mm Hg. Spontaneous hypertensive rats with a mean blood pressure of 180 +/- 5 mm Hg had a gastric emptying rate of 51.9 +/- 6.1%. These data indicate that NO synthase inhibitors given i.v. at doses that inhibit NO synthase, delay gastric emptying through mechanisms which are unrelated to changes in arterial blood pressure.

CGRP 8-37[correction of 8-27] blocks the inhibition of gastric emptying induced by intravenous injection of alpha-CGRP in rats.

The receptor subtype mediating rat alpha-calcitonin gene-related peptide (alpha-CGRP)-induced inhibition of gastric emptying of a non nutrient solution was tested in conscious rats using the CGRP1 receptor antagonist, CGRP 8-37, and the CCK antagonist, MK-329. Intravenous injection of alpha-CGRP (0.5 micrograms) decreased gastric emptying to 26.5 +/- 5.8% from 46.4 +/- 3.9% in vehicle-treated group. Intravenous injection of CGRP 8-37 (15 micrograms) did not influence gastric emptying but completely prevented alpha-CGRP inhibitory effect whereas the 47% delay in gastric emptying induced by intravenous cholecystokinin-8 (CCK, 0.25 microgram) was not modified. The CCK antagonist, MK-329 (1 mg) reversed CCK- but not alpha-CGRP-induced delay in gastric emptying. These results demonstrate that CGRP 8-37 is a specific tool to block alpha-CGRP inhibitory action on gastric motor function and suggest that gastric stasis elicited by peripheral injection of alpha-CGRP may involve an interaction with a CGRP1 receptor subtype.

Stress-induced changes in the gastrointestinal motor system.

Several autonomic, hormonal, behavioural and neuropeptidergic bodily responses to stressful stimuli have been described over the past few decades. Both animal models and human paradigms have been explored. It is acknowledged that stress modulates gastrointestinal (GI) motility through central mechanisms including corticotropin-releasing-factor. This process requires the integrity of autonomic neural pathways. It has become evident that the effects of stress on GI motility vary according to the stressful stimulus, its intensity, the animal species under study and the time course of the study. Recent evidence suggests that chronic or possibly permanent changes develop in enteric smooth muscle properties in response to stress. In animals, the most consistent findings include retardation of gastric emptying in response to various stressors; acceleration of gastric emptying upon cold stress, presumably through the secretion of brain thyroglobulin-hormone; acceleration of intestinal transit; and stimulation of colonic transit and fecal output. In humans, the cold water immersion test has been associated with an inhibition of gastric emptying, while labyrinthine stimulation induces the transition from postprandial to fasting motor patterns in the stomach and the small bowel. Psychological stress has been shown to induce a reduction in the number and amplitude of intestinal migrating motor complexes and to neither affect nor stimulate colonic motility. These various responses to stress are presumably attributed to the preferential activation of specific neuronal pathways under the influence of a given stimulus or its intensity. The significance of these findings and the directions of further studies are discussed.

The economic burden of irritable bowel syndrome in Canada.

In the treatment of irritable bowel syndrome (IBS), medical practitioners and policymakers face the task of providing both high quality and cost effective medical care for a condition with no certain cure. To date, studies have examined only total medical costs to patients with symptoms consistent with an IBS diagnosis. However, these studies have not examined the direct and indirect costs incurred in the course of treatment for IBS, excluding the costs of unrelated medical conditions. Because patients with IBS have been shown to differ significantly from non-IBS patients in their desire to seek medical care, one cannot consider solely the cost differential in medical costs for IBS and non-IBS patients. The present study examines a set of patients who have been diagnosed with IBS and seek medical care for IBS.

Surgical removal of a granulosa cell tumor from a heifer.

A twelve month old, noncycling Holstein-Friesian heifer, was examined because of abnormal udder development. Rectal palpation revealed a tense right uterine horn. A solid mass in the right abdomen was detected by ballottement. A granulosa cell tumor of the right ovary was removed and nine months later the animal conceived.

Interdigestive intestinal motility in dogs with chronic exclusion of bile from the digestive tract.

To elucidate the role of bile delivery into the duodenum on the regulation of plasma motilin and on the interdigestive migrating complex, three dogs were operated upon to ligate the main bile duct and divert the biliary flow into the urinary bladder via a Foley catheter. After the operation, despite the chronic diversion of bile from the digestive tract, all animals maintained an excellent health status and exhibited recurrent periods of phase III motor activity migrating from the duodenum to the ileum, which were associated with cyclic increases in plasma motilin. Following the infusion of pooled dog bile (1 mL/min for 10 min) into the duodenum, a premature phase III and a concomitant rise in plasma motilin were observed. These results suggest, that although bile delivery into the duodenum can induce motilin increase in plasma and period of phase III activity in the gut, this phenomenon does not constitute an essential stimulus for the release of motilin and for the induction of the phase III of the interdigestive migrating complex.

Abdominal surgery-induced inhibition of gastric emptying is mediated in part by interleukin-1 beta.

The role of interleukin-1 beta (IL-1 beta) in abdominal surgery-induced inhibition of gastric emptying was investigated. Abdominal surgery was performed under halothane anesthesia, and 5 min later, the 20-min rate of gastric emptying was measured by the phenol red method in conscious animals. In nonoperated animals, intravenous IL-1 beta dose dependently decreased gastric emptying from 55.1 +/- 1.7% in controls to 8.0 +/- 3.5% (P < 0.05) after treatment with 1 microgram IL-1 beta. Prior administration of IL-1 beta receptor antagonist (IL-1 beta ra; 200 micrograms) completely abolished the inhibitory effects of IL-1 beta. Surgery inhibited gastric emptying by 83.4% compared with rats receiving anesthesia alone. IL-1 beta ra (200 micrograms) reversed the inhibition of gastric emptying by 34.8% (P < 0.05) in the early (30 min) postoperative period and by 32.3% (P < 0.05) in the late (120 min) postoperative period. Use of calcitonin gene-related peptide-(8-37) [CGRP-(8-37)] in combination with IL-1 beta ra in operated animals resulted in no further reversal in the inhibition of gastric emptying: CGRP-(8-37)-treated animals = 42.1 +/- 4.1%; CGRP-(8-37) + IL-1 beta ra = 38.0 +/- 4.4% (not significant). Moreover, in nonoperated animals, CGRP-(8-37) completely abolished the effects of intravenous IL-1 beta on gastric emptying: IL-1 beta-treated animals = 11.1 +/- 2.0%; IL-1 beta + CGRP-(8-37) = 40.6 +/- 6.4% (P < 0.05). These results suggest that IL-1 beta is mediating part of the gastric ileus observed after abdominal surgery through the release of CGRP from the visceral afferents.

Calcitonin gene-related peptide in viscerosensitive response to colorectal distension in rats.

The role of calcitonin gene-related peptide (CGRP) on colorectal distension-induced visceral pain was investigated in conscious rats. Intracolonic administration of acetic acid (0.6%) resulted in a significantly increased number of abdominal contractions in response to colorectal balloon distension from 5.8 +/- 1.2 in controls to 16.6 +/- 1.0 in acetic acid-treated animals (P < 0.05), evidencing sensitization of visceral afferent pathways and subsequently visceral hyperalgesia. This sensitization phenomenon was not observed in animals previously treated with systemic capsaicin. Likewise, in animals not treated with capsaicin, use of an intravenous antagonist for CGRP [human CGRP-(8-37)], completely reversed the sensitizing effects of acetic acid. Furthermore, intravenous administration of CGRP dose dependently increased the number of abdominal contractions in response to colorectal distension from 3.0 +/- 1.1 (CGRP 250 ng) to 17.0 +/- 1.2 (CGRP 500 ng, P < 0.05), as previously observed in acetic acid-treated animals. Finally, intrathecal administration of hCGRP-(8-37) (mid-lumbar) also resulted in a total dose-dependent reversal of CGRP (500 ng) or acetic acid-induced visceral hypersensitivity. These results demonstrate that CGRP plays a major role in this model of visceral afferent nerve sensitization from gastrointestinal origin.

Intravenous interleukin-1-beta-induced inhibition of gastric emptying: involvement of central corticotrophin-releasing factor and prostaglandin pathways in rats.

The role of corticotrophin-releasing factor (CRF) and prostaglandin in interleukin-1 beta (IL-1 beta)-induced delayed gastric emptying was investigated. Gastric emptying was monitored 20 min after orogastric delivery of a methylcellulose phenol red solution in fasted rats injected intravenously with IL-1 beta at the ED50 dose (3 ng/rat) 30 min before the non-caloric solution. The IL-1 receptor antagonist (IL-1ra) injected intravenously (3 micrograms/rat) or intracisternally (100 ng/rat) reversed the IL-1 beta-induced 47% inhibition of gastric emptying by 100% and 62%, respectively. The new CRF antagonist [DPhe12, Nle21,38, C alpha MeLeu37]-CRF12-41 (20 micrograms/rat), injected intracisternally, or indomethacin (5 mg/kg i.p.) completely abolished IL-1 beta (3 ng/rat i.v.)-induced gastric stasis. The CRF antagonist injected intravenously (20 micrograms/rat) did not influence the IL-1 beta inhibitory action. None of the pretreatments given alone influenced basal gastric emptying. These data suggest that peripheral IL-1 beta-induced inhibition of gastric emptying is mediated by specific IL-1 receptor interactions and brain CRF pathways requiring the integrity of eicosanoid-cyclooxygenase pathways.

Aniline hydroxylation and 7-ethoxycoumarin O-deethylation activities in solubilized and partially resolved liver cytochromes P-450 from ethanol-fed rats.

Chronic ethanol administration in female rats enhances the apparent molar activity of liver microsomes for aniline hydroxylation and 7-ethoxycoumarin O-deethylation. Microsomal cytochromes P-450 from ethanol-fed and control rats have been solubilized and partially resolved in six fractions by anion-exchange chromatography. Induction of aniline hydroxylase activity by ethanol was associated with marked increases in the turnover numbers of the more basic cytochrome P-450 containing fractions in a reconstituted aniline hydroxylation system. Cytochrome P-450, exhibiting by far the highest 7-ethoxycoumarin O-deethylase activity, was eluted in a relatively acidic fraction; its turnover number with 7-ethoxycoumarin after ethanol consumption, however, did not differ significantly from that of the corresponding fraction from control microsomes. These observations suggest that induction of liver microsomal mixed function oxidases by ethanol may reflect the contribution of more than one cytochrome P-450 isozyme.