Relating gastric scintigraphy and symptoms to motility capsule transit and pressure findings in suspected gastroparesis

BACKGROUND

Wireless motility capsule (WMC) findings are incompletely defined in suspected gastroparesis. We aimed to characterize regional WMC transit and contractility in relation to scintigraphy, etiology, and symptoms in patients undergoing gastric emptying testing.

METHODS

A total of 209 patients with gastroparesis symptoms at NIDDK Gastroparesis Consortium centers underwent gastric scintigraphy and WMCs on separate days to measure regional transit and contractility. Validated questionnaires quantified symptoms.

KEY RESULTS

Solid scintigraphy and liquid scintigraphy were delayed in 68.8% and 34.8% of patients; WMC gastric emptying times (GET) were delayed in 40.3% and showed 52.8% agreement with scintigraphy; 15.5% and 33.5% had delayed small bowel (SBTT) and colon transit (CTT) times. Transit was delayed in ≥2 regions in 23.3%. Rapid transit was rarely observed. Diabetics had slower GET but more rapid SBTT versus idiopathics (P ≤ .02). GET delays related to greater scintigraphic retention, slower SBTT, and fewer gastric contractions (P ≤ .04). Overall gastroparesis symptoms and nausea/vomiting, early satiety/fullness, bloating/distention, and upper abdominal pain subscores showed no relation to WMC transit. Upper and lower abdominal pain scores (P ≤ .03) were greater with increased colon contractions. Constipation correlated with slower CTT and higher colon contractions (P = .03). Diarrhea scores were higher with delayed SBTT and CTT (P ≤ .04).

CONCLUSIONS & INFERENCES

Wireless motility capsules define gastric emptying delays similar but not identical to scintigraphy that are more severe in diabetics and relate to reduced gastric contractility. Extragastric transit delays occur in >40% with suspected gastroparesis. Gastroparesis symptoms show little association with WMC profiles, although lower symptoms relate to small bowel or colon abnormalities.

Diabetic and idiopathic gastroparesis is associated with loss of CD206-positive macrophages in the gastric antrum

BACKGROUND

Animal studies have increasingly highlighted the role of macrophages in the development of delayed gastric emptying. However, their role in the pathophysiology of human gastroparesis is unclear. Our aim was to determine changes in macrophages and other cell types in the gastric antrum muscularis propria of patients with diabetic and idiopathic gastroparesis.

METHODS

Full thickness gastric antrum biopsies were obtained from patients enrolled in the Gastroparesis Clinical Research Consortium (11 diabetic, 6 idiopathic) and 5 controls. Immunolabeling and quantitative assessment was done for interstitial cells of Cajal (ICC) (Kit), enteric nerves protein gene product 9.5, neuronal nitric oxide synthase, vasoactive intestinal peptide, substance P, tyrosine hydroxylase), overall immune cells (CD45) and anti-inflammatory macrophages (CD206). Gastric emptying was assessed using nuclear medicine scintigraphy and symptom severity using the Gastroparesis Cardinal Symptom Index.

RESULTS

Both diabetic and idiopathic gastroparesis patients showed loss of ICC as compared to controls (Mean [standard error of mean]/hpf: diabetic, 2.28 [0.16]; idiopathic, 2.53 [0.47]; controls, 6.05 [0.62]; P=.004). Overall immune cell population (CD45) was unchanged but there was a loss of anti-inflammatory macrophages (CD206) in circular muscle (diabetic, 3.87 [0.32]; idiopathic, 4.16 [0.52]; controls, 6.59 [1.09]; P=.04) and myenteric plexus (diabetic, 3.83 [0.27]; idiopathic, 3.59 [0.68]; controls, 7.46 [0.51]; P=.004). There was correlation between the number of ICC and CD206-positive cells (r=.55, P=.008). Enteric nerves (PGP9.5) were unchanged: diabetic, 33.64 (3.45); idiopathic, 41.26 (6.40); controls, 46.80 (6.04).

CONCLUSION

Loss of antral CD206-positive anti-inflammatory macrophages is a key feature in human gastroparesis and it is associates with ICC loss.

Nausea and vomiting in gastroparesis: similarities and differences in idiopathic and diabetic gastroparesis

BACKGROUND

Nausea and vomiting are classic symptoms of gastroparesis. It remains unclear if characteristics of nausea and vomiting are similar in different etiologies of gastroparesis. The aims of this article were as follows: to describe characteristics of nausea and vomiting in patients with gastroparesis and to determine if there are differences in nausea and vomiting in diabetic (DG) and idiopathic gastroparesis (IG).

METHODS

Gastroparetic patients enrolling in the NIDDK Gastroparesis Registry underwent assessment with history and questionnaires assessing symptoms, quality of life, and a questionnaire characterizing nausea and vomiting.

KEY RESULTS

Of 159 gastroparesis patients (107 IG, 52 DG), 96% experienced nausea, whereas 65% experienced vomiting. Nausea was predominant symptom in 28% and vomiting was predominant in 4%. Nausea was severe or very severe in 41%. PAGI-SYM nausea/vomiting subscore was greater with increased vomiting severity, but not nausea severity in DG than IG. Nausea was related to meals in 71%; lasting most of the day in 41%. Increasing nausea severity was related to decreased quality of life. Nausea often preceded vomiting in 82% of patients and vomiting often relieved nausea in 30%. Vomiting was more common in DG (81%) compared to IG (57%; p = 0.004). Diabetic patients more often had vomiting in the morning before eating, during the night, and when not eating.

CONCLUSIONS & INFERENCES

Nausea is present in essentially all patients with gastroparesis irrespective of cause and associated with decreased quality of life. In contrast, vomiting was more prevalent, more severe, and occurred more often in DG than IG. Thus, characteristics of vomiting differ in IG vs DG.

Evaluation of the pylorus with concurrent intraluminal pressure and EndoFLIP in patients with nausea and vomiting

BACKGROUND

Nausea and vomiting occurs in gastroparesis due to diabetes mellitus or unknown causes. The aim of this study was to compare (i) pyloric distensibility to pyloric manometric pressure in patients with nausea and vomiting and (ii) to correlate distensibility with delays in gastric emptying.

METHODS

Sleeve manometry and EndoFLIP were performed sequentially during the same endoscopy on 114 patients with nausea and vomiting (47 with diabetes mellitus and 67 with idiopathic cause) after a standardized gastric emptying study. The sleeve manometer was positioned fluoroscopically, and the EndoFLIP was placed endoscopically. Manometric pressure using a water-perfused catheter and distensibility using an EndoFLIP filled with 40 cc of saline were measured from the pylorus.

KEY RESULTS

The basal pyloric pressure was elevated (>10 mmHg) in 34 patients and was normal in 80 patients. The basal and peak pressures were similar in patient with normal and delayed gastric emptying (p > 0.05). There was a significant decrease in distensibility (8.0 ± 1.0 mm(2) /mmHg) in patients with gastric retention (>20% at 4 h) compared with patients (12.4 ± 1.4 mm(2) /mmHg) (p < 0.01) with normal gastric retention (<10%). Pressure measurements from the sleeve manometer and the EndoFLIP correlated (r = 0.29) (p < 0.002), and increased EndoFLIP balloon pressure (19.4 ± 1.4 mmHg) (p < 0.01) was associated with a severe delay in gastric emptying.

CONCLUSIONS & INFERENCES

Elevated basal pyloric pressure occurs in 42% of patients with nausea and vomiting and delayed emptying. Decreased pyloric distensibility occurs with nausea, vomiting, and delayed gastric emptying. The EndoFLIP is a useful tool in the evaluation of pyloric function in symptomatic patients.

Factors related to abdominal pain in gastroparesis: contrast to patients with predominant nausea and vomiting

BACKGROUND

Factors associated with abdominal pain in gastroparesis are incompletely evaluated and comparisons of pain vs other symptoms are limited. This study related pain to clinical factors in gastroparesis and contrasted pain/discomfort- with nausea/vomiting-predominant disease.

METHODS

Clinical and scintigraphy data were compared in 393 patients from seven centers of the NIDDK Gastroparesis Clinical Research Consortium with moderate-severe (Patient Assessment of Upper Gastrointestinal Disorders Symptoms [PAGI-SYM] score ≥ 3) vs none-mild (PAGI-SYM < 3) upper abdominal pain and predominant pain/discomfort vs nausea/vomiting.

KEY RESULTS

Upper abdominal pain was moderate-severe in 261 (66%). Pain/discomfort was predominant in 81 (21%); nausea/vomiting was predominant in 172 (44%). Moderate-severe pain was more prevalent with idiopathic gastroparesis and with lack of infectious prodrome (P ≤ 0.05) and correlated with scores for nausea/vomiting, bloating, lower abdominal pain/discomfort, bowel disturbances, and opiate and antiemetic use (P < 0.05), but not gastric emptying or diabetic neuropathy or control. Gastroparesis severity, quality of life, and depression and anxiety were worse with moderate-severe pain (P ≤ 0.008). Factors associated with moderate-severe pain were similar in diabetic and idiopathic gastroparesis. Compared to predominant nausea/vomiting, predominant pain/discomfort was associated with impaired quality of life, greater opiate, and less antiemetic use (P < 0.01), but similar severity and gastric retention.

CONCLUSIONS & INFERENCES

Moderate-severe abdominal pain is prevalent in gastroparesis, impairs quality of life, and is associated with idiopathic etiology, lack of infectious prodrome, and opiate use. Pain is predominant in one fifth of gastroparetics. Predominant pain has at least as great an impact on disease severity and quality of life as predominant nausea/vomiting.

Clinical-histological associations in gastroparesis: results from the Gastroparesis Clinical Research Consortium

BACKGROUND

Cellular changes associated with diabetic (DG) and idiopathic gastroparesis (IG) have recently been described from patients enrolled in the Gastroparesis Clinical Research Consortium. The association of these cellular changes with gastroparesis symptoms and gastric emptying is unknown. The aim of this study was to relate cellular changes to symptoms and gastric emptying in patients with gastroparesis.

METHODS

Earlier, using full thickness gastric body biopsies from 20 DG, 20 IG, and 20 matched controls, we found decreased interstitial cells of Cajal (ICC) and enteric nerves and an increase in immune cells in both DG and IG. Here, demographic, symptoms [gastroparesis cardinal symptom index score (GCSI)], and gastric emptying were related to cellular alterations using Pearson's correlation coefficients.

KEY RESULTS

Interstitial cells of Cajal counts inversely correlated with 4 h gastric retention in DG but not in IG (r = -0.6, P = 0.008, DG, r = 0.2, P = 0.4, IG). There was also a significant correlation between loss of ICC and enteric nerves in DG but not in IG (r = 0.5, P = 0.03 for DG, r = 0.3, P = 0.16, IG). Idiopathic gastroparesis with a myenteric immune infiltrate scored higher on the average GCSI (3.6 ± 0.7 vs 2.7 ± 0.9, P = 0.05) and nausea score (3.8 ± 0.9 vs 2.6 ± 1.0, P = 0.02) as compared to those without an infiltrate.

CONCLUSIONS & INFERENCES

In DG, loss of ICC is associated with delayed gastric emptying. Interstitial cells of Cajal or enteric nerve loss did not correlate with symptom severity. Overall clinical severity and nausea in IG is associated with a myenteric immune infiltrate. Thus, full thickness gastric biopsies can help define specific cellular abnormalities in gastroparesis, some of which are associated with physiological and clinical characteristics of gastroparesis.

Long-term safety of tegaserod in patients with constipation-predominant irritable bowel syndrome

BACKGROUND

Tegaserod is a 5-hydroxytryptamine-4 receptor partial agonist. Oral administration causes gastrointestinal effects resulting in increased gastrointestinal motility and attenuation of visceral sensation.

AIM

: To determine the long-term safety and tolerability of tegaserod in patients suffering from irritable bowel syndrome with constipation as the predominant symptom of altered bowel habits.

METHOD

A multicentre, open-label study with flexible dose titration of tegaserod in out-patients suffering from constipation-predominant irritable bowel syndrome.

RESULTS

A total of 579 patients with constipation-predominant irritable bowel syndrome were treated with tegaserod. Of these, 304 (53%) completed the trial. The most common adverse events, classified as related to tegaserod for any dose, were mild and transient diarrhoea (10.1%), headache (8.3%), abdominal pain (7.4%) and flatulence (5.5%). Forty serious adverse events were reported in 25 patients (4.4% of patients) leading to discontinuation in six patients. There was one serious adverse event, acute abdominal pain, classified as possibly related to tegaserod. There were no consistent differences in adverse events between patients previously exposed to tegaserod and those treated de novo. No pattern-forming tegaserod-related abnormalities in haematological and biochemical laboratory tests, urinalysis, blood pressure, pulse rate or electrocardiograms were found.

CONCLUSIONS

Tegaserod appears to be well tolerated in the treatment of patients with constipation-predominant irritable bowel syndrome. The adverse event profile, clinical laboratory evaluations, vital signs and electrocardiogram recordings revealed no evidence of any unexpected adverse events, and suggest that treatment is safe over a 12-month period.

Role of colonic motility in guiding therapy in patients with constipation

Constipation is a common condition defined by less than three bowel movements per week. Often constipation is secondary to altered motility of the colon. Tests that measure colonic motility lead the clinician to appropriate therapy. Colonic transit measured with either radionuclides or radio-opaque markers determine whether the transit through the colon is truly slow, and then identify the potential region of the colon that impedes the movement of intraluminal contents. Patients with normal colonic transit do not require further evaluation of their colonic motor function. Colonic and anorectal manometry differentiate patients in to 3 groups: (1) functional anal outlet obstruction; (2) uncoordinated distal colonic phasic contractions, and (3) colonic inertia. Functional outlet obstruction may be treated successfully by increasing the water content of their stools and biofeedback. Antispasmodics including anticholinergics, nitrates and calcium channel blockers may decrease the functional obstruction caused by phasic colonic contractions. The prokinetics such as cisapride have successfully improved constipation due to colonic inertia, Parkinson's disease or spinal cord injury as well as idiopathic inertia. Occasionally patients with inertia may require colectomy with ileorectal anastomosis to treat severe constipation.

Effect of leuprolide acetate in treatment of abdominal pain and nausea in premenopausal women with functional bowel disease: a double-blind, placebo-controlled, randomized study

We have previously reported impressive results in using a gonadotropin-releasing hormone analog, leuprolide acetate (Lupron), in the treatment of moderate to severe symptoms (especially abdominal pain and nausea) in patients with functional bowel disease (FBD). Pain is the hallmark of patients with FBD, and there is no consistent therapy for the treatment of these patients. The purpose of the present study was to expand the investigation to study similar patients (menstruating females) in a multicenter, double-blind, placebo-controlled, randomized study using Lupron Depot (which delivers a continuous dose of drug for one month), 3.75 mg (N = 32) or 7.5 mg (N = 33), or placebo (N = 35) given intramuscularly every four weeks for 16 weeks. Symptoms were assessed using daily diary cards to record abdominal pain, nausea, vomiting, early satiety, anorexia, bloating, and altered bowel habits. Additional assessment tools were quality of life questionnaires, psychological profile, oral-to-cecal transit using the hydrogen breath test, antroduodenal manometry, reproductive hormone levels, and global evaluations by both patient and investigator. Patients in both Lupron Depot-treated groups showed consistent improvement in symptoms; however, only the Lupron Depot 7.5 mg group showed a significant improvement for abdominal pain and nausea compared to placebo (P < 0.001). Patient quality of life assessments and global evaluations completed by both patient and investigators were highly significant compared to placebo (P < 0.001). All reproductive hormone levels significantly decreased for both Lupron Depot-treated groups by week 4 and were significantly different compared to placebo at week 16 (P < 0.001). This study shows that leuprolide acetate is effective in controlling the debilitating symptoms of abdominal pain and nausea in patients with FBD.

Role of motility measurements in managing upper gastrointestinal dysfunction

Nausea, vomiting, and abdominal pain are common symptoms that suggest many diagnoses. The patient's symptoms may be related to an anatomical defect such as a peptic ulcer or a mechanical small bowel obstruction. However, no anatomical abnormality may be identified despite radiological, endoscopic, or laboratory studies. The cause of the patient's symptoms may have significant impact on the patient's quality of life (nonulcer dyspepsia) and life span (intestinal pseudo-obstruction). Abnormal antroduodenal motility may be the underlying cause of the patient's symptoms. Normally, coordinated phasic contractions in the stomach and small intestine maintain digestion and absorption of food. A prolonged set of phasic contractions (phase 3 of the migrating complex) begins in the stomach and propagates down the small intestine to excrete nondigestible foods, bacteria, and dead cells. Any disturbance in the normal motility pattern can lead to maldigestion and symptoms of upper intestinal dysfunction. Objective tests of motility disturbances in the stomach and small intestine include measurement of gastric emptying, intestinal transit, contractions of the stomach and duodenum, and electrogastrography. Abnormal antroduodenal motility may be secondary to an abnormality in the smooth muscle (myopathy) or the nerves in controlling smooth muscle contractions (neuropathy). Antroduodenal motility measurements may help identify a partial small bowel obstruction, the cause of small intestinal overgrowth, and the cause of chronic abdominal visceral pain. Motility studies may suggest useful drugs for correcting the underlying pathophysiology and relieving symptoms.

Clinical considerations in GERD (gastroesophageal reflux disease) therapy: focus on cisapride

Heartburn, the major symptom of gastrointestinal reflux disease (GERD), is a common condition that is usually self-treated with over-the-counter products. For patients with severe or recurrent symptoms of GERD, pharmacologic therapy includes acid suppression with H2-receptor antagonists and proton pump inhibitors, and, alternatively, the use of prokinetic agents. While all of these are efficacious, given its high efficacy in nonerosive and mild-to-moderate erosive esophagitis, the prokinetic agent cisapride deserves significant consideration in this patient population.

Managing the patient with atypical chest pain

Since angina and heartburn can feel the same, excluding cardiac disease may be the first order of business. That done, clinical findings and laboratory tests can help identify the esophageal disturbance. Gastric acid reflux, motility disorders, and visceral nerve hypersensitivity--alone or in combination--can cause chest pain, and each may call for a different pharmacologic regimen.

Expression of insulin-like growth factor I receptors and binding proteins by colonic smooth muscle cells

We recently demonstrated upregulation of insulin-like growth factor I (IGF-I) binding sites in the smooth muscle layer of inflamed rat colon. The increase in binding sites was due to increased expression of IGF binding proteins (IGFBPs), which modulate the effects of IGF. To further study the role of IGF in the colon, we investigated whether cultured colonic smooth muscle cells (SMC) express IGF-I receptors and IGFBPs. SMC were isolated by collagenase digestion from rat colonic smooth muscle and grown in primary culture. Equilibrium binding experiments using (125)I-labeled IGF-I showed the presence of an IGF-I receptor with a dissociation constant of 1.96 nM and a maximal binding constant of 53,000 receptors/cell. Competition binding studies with IGF-II and insulin, together with chemical cross-linking experiments, corroborated this conclusion. Western ligand blotting of conditioned medium and Northern analysis of total RNA demonstrated that the cells expressed and secreted IGFBP-4, -5, and -3 with molecular masses of 25, 31, and 45 kDa, respectively. These results, together with our in vivo studies in the rat, support a role for IGF in tissue fibrosis and stricture formation during chronic intestinal inflammation.

Antibodies in patients with inflammatory bowel disease and the apparent influence of medications

Patients with inflammatory bowel disease (IBD) are known to have increased antibodies to several food and bacterial antigens. To assess selected isotype contributions in greater detail, we examined the concentrations of IgA, IgG, IgE, and IgG4 antibodies to five selected antigens, two of bacterial and three of food origin. Thirty patients with IBD and thirty matched healthy controls were studied. Most antibodies were increased in IBD patients compared to controls. Statistically significant increases were more frequent in Crohn's disease (CD) than in ulcerative colitis (UC). An unexpected finding was that IBD patients treated with sulfasalazine had statistically higher levels of most IgA antibodies than healthy controls, while steroid treated patients had lower levels. These findings suggest differing effects on the immune systems of IBD patients by each of these commonly used drugs.

Antroduodenal manometry in children and adults with severe non-ulcer dyspepsia

BACKGROUND

Nonulcer dyspepsia is common in adults but has been recognized only recently in children.

METHODS

We compared signs, symptoms, and antroduodenal motility findings in 34 children and 35 adults with severe nonulcer dyspepsia.

RESULTS

Symptoms and signs were similar in the two groups. Ten children (29%) and one adult (3%) required tube feedings (p = 0.01). Abdominal surgery had been performed on 6 of 34 (18%) children and 18 of 35 adults (51%) (p < 0.01), without relief of symptoms. Esophageal manometry was abnormal in 5 of 23 (22%) children and 6 of 31 (19%) adults. Antroduodenal manometry was suggestive of neuropathy in 25 children and 26 adults and of myopathy in 3 children and 2 adults. Absence of phase 3 of the migrating motor complex was found in 4 children and 17 adults (p = 0.01). Antroduodenal manometry was normal in six children and seven adults.

CONCLUSION

Signs, symptoms, and discrete manometric abnormalities of childhood nonulcer dyspepsia resembled those of adult nonulcer dyspepsia. Manometric findings in nonulcer dyspepsia resembled those reported in chronic intestinal pseudo-obstruction, suggesting that these conditions are on a continuum of enteric neuromuscular diseases.

Current concepts in the management of the irritable bowel syndrome

In the irritable bowel syndrome gastrointestinal tract motility is disturbed from the esophagus to the colon, causing pain and altered function. When colonic motility is abnormal, the patient can experience either constipation or diarrhea in addition to abdominal pain and bloating. In constipated patients the postprandial colonic motility can increase normally after eating or the colon can remain motionless. Generally propagating contractions are absent in patients with constipation predominant irritable bowel syndrome. Propagating contractions are increased in frequency in patients with diarrhea, although the phasic contractions are decreased. Questionnaires discriminate between patients with structural disease such as ulcerative colitis and patients with functional disease, however they cannot differentiate between the different subgroups of patients with constipation predominant irritable bowel syndrome. Treatment strategies are beginning to focus on the underlying pathophysiologic abnormality.

Colonic manometry in children with chronic intestinal pseudo-obstruction

Pressure changes were evaluated in the transverse, descending, and rectosigmoid colon of 30 children with chronic intestinal pseudo-obstruction. Twenty two had severe lifelong constipation and eight had symptoms suggesting a motility disorder exclusively of the upper gastrointestinal tract. Based on prior antroduodenal manometry, 24 children were diagnosed as having a neuropathic and six a myopathic form of intestinal pseudo-obstruction. On the day of study, endoscopy was used to place a manometry catheter into the transverse colon and intraluminal pressure was recorded for more than four hours. After a baseline recording, we gave a meal to assess the gastrocolonic response. Colonic contractions were noted in 24 children. The six children with no colonic contractions had a hollow visceral myopathy and constipation. In the children with colonic contractions, fasting motility did not differentiate children with and without constipation. After the meal, in all eight children without constipation there was (1) an increase in motility index (3.2 (SEM 0.3) mm Hg/min basal v 8.4 (SEM 1.1) mm Hg/min postprandial; p < 0.001), and (2) at least one high amplitude propagated contraction (HAPC). In the 16 constipated children with colonic contractions the motility index did not significantly increase after the meal (2.1 (SEM 0.3) mm Hg/min basal v 3.1 (SEM 0.4) mm Hg/min postprandial) and 12 of them had no HAPCs (p < 0.01 v group without constipation). In summary, in children with a clinical diagnosis of chronic intestinal pseudo-obstruction, constipation is associated with absence of HAPCs, and the gastrocolonic response or with total absence of colonic contractions. It is concluded that studies of colonic manometry are feasible in children and may document discrete abnormalities in those with intestinal pseudo-obstruction with colonic involvement.

Postnatal changes in receptor-mediated rabbit gastric smooth muscle relaxation

The aims of this study were to identify mediators of relaxation in rabbit proximal gastric circular smooth muscle and to assess age-dependent changes in tissue response. Vasoactive intestinal peptide (VIP), adenosine, and norepinephrine induced tetrodotoxin-insensitive, concentration-dependent relaxation in bethanechol-precontracted (3 microM) gastric muscle strips from newborns and weanlings. Maximally effective concentrations of 10 microM VIP induced complete relaxation in newborns, but only 30% relaxation in weanlings (p < 0.01). Maximally effective concentrations of adenosine induced complete relaxation at both ages. Adenosine (ED50 3 microM) was more potent than adenosine triphosphate, indicating the presence of P1 purinergic receptors. In newborns norepinephrine induced complete relaxation (ED50 0.5 microM). The response to norepinephrine changed in age-dependent increments from relaxation in newborns to strong contraction in weanlings. In weanlings phentolamine inhibited norepinephrine-stimulated contraction, revealing persistent propranolol-sensitive relaxation. Tetrodotoxin and atropine had no effect on norepinephrine-stimulated contraction. In summary, in rabbit gastric circular smooth muscle: (1) VIP, adenosine, and norepinephrine induce relaxation; (2) VIP loses efficacy with age; (3) there is a beta-adrenergic receptor mediating relaxation in the newborn which persists, and (4) an alpha-adrenergic receptor mediating contraction emerges early in postnatal life. Age-dependent changes in response to VIP and norepinephrine may contribute to the postnatal maturation of the gastric motility.

Characterization of colonic circular smooth muscle cells in culture

The receptor-binding properties of isolated rabbit colonic circular smooth muscle cells in primary culture have been investigated. In intact smooth muscle, acetylcholine, acting through M2 muscarinic receptors, and vasoactive intestinal polypeptide (VIP), acting through VIP receptors, are two of the principal neurotransmitters mediating contraction and relaxation, respectively. The muscarinic receptor was present in very high levels (600,000 receptors/cell) on freshly isolated colonic smooth muscle cells as shown by binding of the muscarinic receptor antagonist N-methylscopolamine (NMS). However, NMS binding sites decreased rapidly when the cells were placed in primary culture. After 21 h in culture, specific binding of [3H]NMS decreased to 20%, and after 48 h to less than 10% that of preculture values. This loss was not associated with a change in receptor affinity, since Kd was unchanged for the receptors still present. In contrast, high-affinity VIP receptors were expressed on cultured smooth muscle cells but could not be detected on freshly isolated cells. Cultured cells responded to VIP with an increase in intracellular adenosine 3',5'-cyclic monophosphate (cAMP), indicating that the VIP receptors were functionally coupled to adenylate cyclase. Cultured cells also responded to calcitonin gene-related peptide (CGRP) and forskolin with increased production of intracellular cAMP. In contrast, neither VIP nor CGRP elicited an increase in intracellular cAMP when added to freshly isolated cells. Furthermore, freshly isolated cells had a greatly diminished response to forskolin, suggesting that the isolation procedure not only destroyed cell surface receptors for VIP and CGRP, but also damaged the cells sufficiently to decrease cellular adenylate cyclase activity.(ABSTRACT TRUNCATED AT 250 WORDS)

An abnormal rate of actin myosin cross-bridge cycling in colonic smooth muscle associated with experimental colitis

Previous studies showed that colonic smooth muscle develops less contractile force to neurohumoral stimulation when associated with mucosal inflammation. This study evaluated 1) the Ca2+ dependence for colonic smooth muscle contraction, 2) the maximum velocity of muscle shortening (Vmax), and 3) changes in 20-kDa myosin light-chain (MLC) phosphorylation in distal circular colonic muscle from healthy rabbits and from rabbits with experimental colitis, induced by Formalin and immune complexes. The isometric tension of unskinned muscle stimulated with bethanechol or KCl was less (P less than 0.05) in animals with colitis compared with the control group. In saponin-skinned muscle, the amplitude of the maximal tension at [Ca2+] of 3 x 10(-7) M was decreased (P less than 0.05) in colitis animals (4.3 +/- 0.9 x 10(4) N/m2, n = 7) compared with healthy animals (10.5 +/- 2.4 x 10(4) N/m2, n = 6). However, the ED50 for Ca2+ stimulation was similar (P greater than 0.05) in both groups. When MLC was thiophosphorylated with ATP gamma S, the tension development was decreased in colitis (2.1 +/- 0.3 x 10(4) N/m2, n = 5; P less than 0.01) compared with normals (5.0 +/- 1.4 x 10(4) N/m2, n = 5). In healthy animals, phosphorylation of 20-kDa MLC increased rapidly to 51.2 +/- 3.1% within 15 s after stimulation and subsequently declined to 19.0 +/- 2.1% at 5 min. Vmax was maximal (0.14 Lo/s) 13 s after stimulation and declined before maximal active isometric stress. In colitis animals, the 20-kDa MLC phosphorylation (P less than 0.05) and the Vmax (P less than 0.01) were decreased.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of cell culture on rabbit colonic smooth muscle bradykinin receptors

The aim of this study was to assess the effect of cell culture on the bradykinin receptor of rabbit colon myocytes. In longitudinal muscle strips prepared from distal colon, bradykinin stimulated dose-dependent contraction that was 62% of the maximal response to bethanecol. At 4 degrees C, [3H]bradykinin binding to fresh muscle homogenates from the distal colon was time dependent, saturable, and linearly related to tissue concentration. Specific binding of 0.6 nmol/L [3H]bradykinin was 80% +/- 2% of total binding. In competitive binding studies, Hill coefficients approached unity, suggesting the presence of a single class of receptors. The order of potency was bradykinin greater than [D-Phe7]bradykinin much greater than des-Arg9, [Leu8]bradykinin, which is consistent with results of a B2 receptor subclass. Colon myocytes from the longitudinal muscle layer achieved confluence and were harvested for studies after 12-14 days in culture. Bradykinin receptors were of high affinity [disassociation constant (Kd) = 672 pmol/L] and numbered 10,217 +/- 2567/cell. To show that the receptors on cultured myocytes were functional, the effect of bradykinin was measured (a) on intracellular calcium concentration using Fura 2 and (b) on prostaglandin E2 concentration in the culture media using radioimmunoassay. In cells grown to confluence on cover slips and preloaded with Fura 2, bradykinin stimulated the threshold response at 1 nmol/L and maximal response (increased intracellular calcium concentration from 229 to 633 nmol/L) at 1 mumol/L. Bradykinin, 100 nmol/L, increased Prostaglandin E2 in the culture media threefold. In summary, colon myocytes express functioning bradykinin receptors, which, unlike muscarinic receptors, persist in culture. Bradykinin appears to be a suitable agonist for studies of receptor-mediated intracellular events in cultured colon myocytes.

Postnatal changes in the substance P receptor on rabbit gastric smooth muscle

We used radioligand binding to tissue homogenates and isometric contraction of muscle strips to characterize the substance P (SP) receptor on gastric smooth muscle from 1- (newborn) and 7-day-old and 4- and 11-wk-old (weanling) rabbits. Scatchard analysis for newborns was curvilinear, suggesting the presence of multiple binding sites. In newborns the dissociation constant (Kd) of high-affinity binding site was 2.2 +/- 0.3 nM, and the maximum binding (Bmax) was 0.57 +/- 0.06 pmol/mg DNA. The number of high-affinity binding sites decreased with age, disappearing by 11 wk. The Kd for the low-affinity site was more than two orders of magnitude greater than that of the high-affinity site. In competitive binding studies with [3H]SP, the order of potency for the neurokinins was SP much greater than neurokinin A (NKA) greater than neurokinin B (NKB), suggesting that the high-affinity binding sites were NK-1 receptors. [125I]NKA is also bound to newborn tissue homogenate with high affinity. With [125I]NKA the order was NKA greater than SP greater than NKB, suggesting that NK-2 receptors were also present. In contraction studies, atropine and tetrodotoxin had no effect on tachykinin-stimulated contraction, suggesting solely myogenic tachykinin effects on this tissue. In newborn rabbits, the potency and efficacy of SP and NKA were similar. The half-maximal effective dose (ED50) of SP was nearly two orders of magnitude less in newborn rabbits than in weanlings; the potency of NKA did not change.(ABSTRACT TRUNCATED AT 250 WORDS)

Mechanisms of cAMP-mediated relaxation of distal circular muscle in rabbit colon

Photolytic release of free adenosine 3',5'-cyclic monophosphate (cAMP) from its caged form was used to evaluate the physiological role of several proposed mechanisms of cAMP-mediated relaxation of circular smooth muscle in the distal rabbit colon. Photolysis of caged cAMP produced a rapid relaxation of bethanechol-contracted distal circular muscle strips that was dependent on ultraviolet exposure time. An increase in release of free cAMP, associated with increased ultraviolet exposure, was confirmed with high-performance liquid chromatography. Vanadate (an ATPase inhibitor) (3 mM) caused a 48% decrease in cAMP-mediated relaxation, while ouabain and a zero K+ bath solution failed to affect relaxation. cAMP-mediated relaxation of KCl-contracted strips was significantly less effective than that of bethanechol-contracted strips. Although this finding suggested that cAMP-mediated relaxation may involve K+ channel modulation, specific (glibenclamide, charybdotoxin) and nonspecific (TEA) K+ channel blockade failed to affect cAMP-mediated relaxation of bethanechol-contracted strips. The photolytic release of cAMP failed to relax Ca(2+)-contracted saponin skinned muscle strips. These studies suggest 1) modulation of Ca2+ pumps plays an important role in this model of relaxation of distal colonic circular muscle in the rabbit colon, 2) modulation of the Na+ pump or sarcolemmal K+ channels may not play an important physiological role in relaxation induced by a rapid rise in intracellular cAMP, and 3) cAMP does not seem to have a significant physiological effect on the Ca2+ sensitivity contractile apparatus.

Defect in colonic smooth muscle contraction in patients with ulcerative colitis

Patients with ulcerative colitis have decreased postprandial colonic contractions. The purpose of this study was to determine whether the smooth muscle from patients with ulcerative colitis responds abnormally in vitro to different stimuli. Circular colonic smooth muscle strips from patients with ulcerative colitis, acute diverticular disease, or adenocarcinoma were stretched to the optimal length and stimulated with electrical field stimulation (EFS), bethanechol, or increased concentrations of extracellular K+. The EFS-stimulated on-contraction was similar in each group, but the off-contraction was decreased in patients with colitis compared with patients with cancer (P less than 0.02) or diverticular disease (P less than 0.01). Bethanechol stimulated a dose-dependent colonic contraction, which was less in the strips from patients with colitis compared with cancer (P less than 0.02) or diverticular disease (P less than 0.05). The response to increased extracellular K+ was less in muscle from patients with colitis (P less than 0.01) than in the other tissues. Muscle from diverticular disease developed greater stress to K+ stimulation than did muscle from cancer (P less than 0.05). These studies suggest that there is a decrease in the force of muscle contraction in colonic muscle obtained from patients with colitis compared with normal muscle resected from patients with cancer or with muscle associated with diverticular disease of the colon. The similar relatively low amplitude of the on-contraction in each group suggests the physiological release of an inhibitory neurotransmitter.

Colonic motility and transit in health and ulcerative colitis

Preprandial and postprandial colonic motility and transit (scintigraphy), with respect to the splenic flexure, were studied in 10 patients with ulcerative colitis and in 9 healthy subjects. The healthy subjects had a postprandial increase in intraluminal pressure that was significantly (P less than 0.03) greater in the descending colon than in other regions of the colon. In ulcerative colitis, the pressure was decreased in all regions compared with healthy subjects, with no significant pressure gradient among different regions. In normal subjects, transit was quiescent during fasting; eating stimulated both antegrade and retrograde transit. In ulcerative colitis, transit was variable before as well as after the meal. Both healthy subjects and patients with ulcerative colitis had more rapid emptying from the splenic flexure into the sigmoid than into the transverse colon. More frequent, low-amplitude, postprandial propagating contractions occurred in ulcerative colitis (P less than 0.05) than in healthy subjects. Propagating contractions were always antegrade and caused a rapid movement of the tracer into the sigmoid. In conclusion, ulcerative colitis is characterized by (a) decreased contractility, (b) increased low-amplitude propagating contractions, and (c) variable transit. These disturbances may accentuate the diarrhea in ulcerative colitis.

Effect of eating on colonic motility and transit in patients with functional diarrhea. Simultaneous scintigraphic and manometric evaluations

The aim of this study was to correlate colonic motility with transit in 8 patients with functional diarrhea compared to 12 healthy subjects. Intraluminal pressure was measured with perfused catheter ports in the transverse colon, splenic flexure, and descending and sigmoid colons. Transit of the luminal contents was measured by following the movement of 99mTC-diethylenetriaminepentaacetic acid instilled as a bolus in the splenic flexure. In patients with diarrhea, the intraluminal marker moved in and out of the transverse and sigmoid colon regions of interest during fasting, unlike healthy subjects, in whom the marker remained in the splenic flexure. After eating, radioactivity immediately increased in both the transverse and sigmoid colons in healthy subjects. In the patients with diarrhea, eating did not alter the marker movement into the different regions of the colon compared with fasting. Within 100 minutes of eating, the intraluminal marker almost disappeared from the regions of interest in patients with diarrhea. Postprandial colonic nonpropagating contractions increased in each region of the colon in healthy subjects; there was only a small postprandial increase in colonic motility in patients with diarrhea. However, the numbers of fasting and postprandial propagating contractions were increased in patients with diarrhea compared with healthy subjects (P less than 0.02). Each propagating contraction moved more tracer in patients with diarrhea than in healthy subjects (P less than 0.05). These studies suggest that (a) in patients with diarrhea, the fluctuation of marker in both transverse and sigmoid colons during the fasting and postprandial periods is associated with decreased nonsegmenting contractions and frequent propagating contractions; and (b) in healthy subjects, the intraluminal marker moved after eating because of a pressure gradient caused by nonpropagating contractions.

Active idiopathic ulcerative colitis in a patient with ongoing HIV-related immunodepression

It is suspected that immune mechanisms are important in the pathogenesis of ulcerative colitis. The following is a case report of a patient with human immunodeficiency virus-related immunodeficiency whose ulcerative colitis ran a course independent of the depression of his peripheral CD4 cells. Thus, peripheral CD4 cells may have little role in the pathogenesis of ulcerative colitis.

U.S. experience with omeprazole in duodenal ulcer. Multicenter double-blind comparative study with ranitidine. The Omeprazole DU Comparative Study Group

To assess the comparative efficacy of omeprazole 20 mg, a proton pump inhibitor, versus ranitidine 150 mg twice a day, an H2-receptor antagonist, in healing duodenal ulcers we performed a randomized, double-blind, multicenter trial in 309 patients with endoscopically diagnosed ulcers. Patients were treated for up to four weeks and were seen at week 2 and at week 4, if unhealed at week 2, for determination of ulcer status by endoscopy, review of daily self-assessment symptom diaries, and clinical laboratory including fasting serum gastrin. Gastrin levels were repeated two weeks after cessation of study medication. Evaluation of baseline demographic and laboratory parameters demonstrated no significant differences between the two groups at entry. At week 2, 42% of the omeprazole and 34% of the ranitidine-treated patients were healed (P = NS). At week 4, there was a 19% advantage in ulcer healing for the omeprazole-treated patients in comparison to those treated with ranitidine (82% vs 63%, respectively, P less than 0.05). Healing of ulcers greater than or equal to 1.0 cm occurred in 83% of those treated with omeprazole versus 37% treated with ranitidine (P less than 0.01). There were no significant differences in rate of pain relief or incidence of clinical laboratory abnormalities. Mean fasting serum gastrin value during treatment increased over the baseline in both groups, (P less than 0.05). The percent change was significantly greater with omeprazole but few patients had elevations above the upper limit of normal for the assay. Both drugs were well tolerated. Omeprazole 20 mg demonstrated superiority in healing duodenal ulcers at four weeks in comparison to ranitidine 150 mg twice daily and was more effective in healing ulcers greater than or equal to 1.0 cm.

The role of a colonic motility disturbance in ulcerative colitis

Alterations in colonic motility appear to exacerbate the symptom of increased frequency of bowel movements in patients with ulcerative colitis. Decreased segmenting contractions allow rapid forward movement of luminal contents accentuating the diarrhea. The decrease in segmenting colonic motility is further exacerbated by increased numbers of propagating contractions. The rapid transport of intraluminal contents with a propagating contractions into a nondistensible rectum may be one explanation for the relative high incidence of fecal incontinence in these patients. The pathogenesis of the decreased segmenting contractions appears due to an electromechanical dissociation resulting from inhibition of myosin light chain phosphorylation. It is possible that several inflammatory mediators including free oxygen radicals decrease smooth muscle cell function.

Anatomic contribution to differences in rabbit colonic muscle contraction

The aim of this study was to determine if differences in the force of contraction in different regions of the rabbit colon are associated with variations in the histology of the corresponding muscle tissues. Circular and longitudinal muscles were isolated from strips of proximal and distal colonic muscle. Muscle strips stretched to L0 were either stimulated to contract or were processed for electron microscopy. Cross-sections of the smooth muscle cells of the taenia coli had a larger perimeter (P less than 0.001) and were surrounded by increased extracellular matrix (28% of the standardized box) compared with the muscle cells from the other sites in the colon (7%-13%) (P less than 0.001). Cross-sections of the proximal circular muscle cells had a smaller perimeter and were present in a greater number than the cells from other areas of the colon. The distal circular muscle generated a larger force than the other muscles after stimulation with bethanechol or K+ (P less than 0.05). The taenia developed less force than the other muscles (P less than 0.05). Bethanechol was a less potent stimulant for the longitudinal muscles than for the circular muscles (P less than 0.05). This study suggests that (1) the decreased efficacy of bethanechol and K+ stimulation of the taenia coli is caused in part by the smaller number of cells that are available to contract and (2) the increased efficacy for the stimulation of the distal circular muscle compared with the proximal circular muscle is unrelated to the mass of muscle and seems to be related to an inherent property of the muscle.

Developmental changes in agonist-mediated colonic smooth muscle contraction in the rabbit

We studied smooth muscle strips from rabbit distal colon to determine age-related changes in length-tension properties and agonist-mediated contraction. Strips from newborn (1-d-old) and weanling (11-wk-old) rabbits were oriented to measure isometric tension in longitudinal muscle. Active tension comprised 47 +/- 4 and 75 +/- 5% of the total tension in the newborn and weanling, respectively. Total and active tensions in the weanling were greater than in the newborn (p less than 0.001). Although the potencies for bethanechol were similar, the maximal response was nearly 9-fold greater in weanlings (6900 +/- 292 mN/cm2) versus newborns (753 +/- 112 mN/cm2), p less than 0.001. Maximal stress increased with age for bethanechol, high extracellular potassium, substance P, neurokinin A, cholecystokinin octapeptide, bombesin, and serotonin. ED50 for bethanechol, substance P, neurokinin A, and bombesin did not change with age. Serotonin was 12 times more potent in newborns versus weanlings (p less than 0.05). In contrast, cholecystokinin octapeptide was five times less potent in newborns (18.6 nM versus 3.4 nM, respectively, p less than 0.05). Substance P-induced contractions were inhibited partially by atropine. We conclude that length-tension properties of longitudinal colonic smooth muscle differ, and responses to agonists increase with age.

Substance P and CGRP mediate motor response of rabbit colon to capsaicin

Primary afferent nerve terminals located in the mammalian gut wall may play a role in region-specific modulation of gastrointestinal motility. In the present study, we sought to characterize the effect of neuropeptides released from these afferents by capsaicin (CAP) on contractile activity of smooth muscle from the distal rabbit colon. CAP caused a release of acetylcholine and immunoreactivity for substance P (SP) and calcitonin gene-related peptide (CGRP) from the muscle coat. CAP caused a dose-dependent transient stimulation of longitudinal muscle contractions, followed by prolonged inhibition of spontaneous but not stimulated contractile activity. The initial stimulation was abolished by the SP antagonist spantide and by atropine. The inhibitory effect was reduced by repeated exposure of muscle to CGRP. The effect of CGRP on spontaneous contractions differed between longitudinal and circular muscle. In longitudinal muscle, a stimulation was preceded by a transient inhibition, whereas in circular muscle, only inhibition was seen. Both effects were resistant to tetrodotoxin. Repeated exposure of circular but not longitudinal muscle to CGRP resulted in a disappearance of the peptide's inhibitory effect. Exogenously applied CGRP was only a weak antagonist of contractions stimulated by SP and bethanechol. These findings suggest that in the rabbit colon at least the following two neuropeptides are released from CAP-sensitive nerve fibers: a neurokinin peptide from nerve terminals located within the myenteric plexus and CGRP from terminals probably located within the circular muscle layer.

Neurokinin inhibition of cholinergic myenteric neurons in canine antrum

Neurokinins regulate gastrointestinal motility by interacting with receptors on both muscle layers and on myenteric plexus neurons. To determine if specific neurokinin (NK) receptor agonists can mediate inhibitory effects on myenteric neurons, we studied the effect of the NK-1 agonist substance P methylester (SPME) and the putative endogenous NK-2 receptor ligand neurokinin A (NKA) on [3H]acetylcholine [( 3H]ACh) release induced by electrical field stimulation from muscle strips cut from the canine gastric antrum. SPME but not NKA caused a dose-dependent inhibition of stimulated [3H]ACh release in tissues containing the myenteric plexus. The inhibition was not seen in longitudinal muscle without myenteric plexus. Pretreatment of tissues with indomethacin or antiserum to vasoactive intestinal polypeptide (VIP) but not naloxone or adrenergic or cholingergic blockade abolished the SPME-induced inhibition. Exogenous VIP stimulated the release of prostaglandin E2 (PGE2) from full thickness strips, and both VIP and PGE2 inhibited [3H]ACh release induced by electrical depolarization. These findings suggest that NK-1 receptor agonists can selectively inhibit stimulated [3H]ACh release and that this inhibition may involve the release of VIP and PGE2 from neurons within the myenteric plexus.

The activation of calcium and calcium-activated potassium channels in mammalian colonic smooth muscle by substance P

1. The regulation of Ca2(+)-activated K+ channels by the agonist substance P in freshly dissociated smooth muscle cells from the rabbit longitudinal colonic muscle was characterized using the patch clamp technique. 2. In the cell-attached recording mode, when pipette and bath solutions contained equal [K+] (126 mM), the Ca2(+)-activated K+ channels showed a linear current-voltage relationship (between -50 mV and 50 mV) with a slope conductance of 210 +/- 35 pS (n = 12). Reversal potential measurements indicated that the channel was highly selective for K+ over Na+ (PK/PNa = 110). 3. Channels were activated by depolarizing membrane voltages and cytosolic Ca2+, and in inside-out patches channel activation depended sigmoidally on voltage and [Ca2+]. The potential for half-activation at a cytosolic [Ca2+] of 5 x 10(-6) M was 0 mV. A tenfold increase in cytosolic Ca2+ resulted in a 60 mV shift of the sigmoidal voltage activation curve to more negative potentials. 4. Threshold concentrations of substance P (10(-12) M), which did not result in cell contraction, caused a prolonged activation of K+ channels. The K+ channels were observed to open in clusters: simultaneous opening of multiple channels was interrupted by complete, prolonged channel closure. 5. Lowering bath [Ca2+] to submicromolar concentrations abolished the effect of substance P. The activation of K+ channels by substance P (10(-12) M) was also inhibited by the dihydropyridine nifedipine (10(-6) M), a blocker of L-type Ca2+ channels. 6. In the whole-cell recording mode, with the pipette solution containing 126 mM-KCl, 0.77 mM-EGTA and 1 mM-ATP, depolarization from a holding potential of -70 mV elicited outward currents which increased to steady-state values. These were K+ currents as they were blocked by TEA (tetraethylammonium, 30 mM) and Ba2+ (1 mM) and were abolished when pipette K+ was replaced by Cs+. 7. The depolarization-activated outward current was not affected by lowering extracellular [Ca2+] or by the Ca2+ channel antagonists Cd2+ (200 microM), nifedipine (10(-6)-10(-5) M) or verapamil (10(-6) M). The current was greatly reduced when the EGTA concentration in the pipette solution was increased from 0.77 to 10 mM. 8. When the pipette solution contained CsCl, membrane depolarization activated inward currents. The peak inward current was identified as current through L-type Ca2+ channels based on its voltage- and time-dependent kinetics, and its modulation by dihydropyridines.(ABSTRACT TRUNCATED AT 400 WORDS)

Developmental changes in agonist-mediated gastric smooth muscle contraction in the rabbit

We studied smooth muscle strips from rabbit proximal stomach to explore the age-related changes in agonist-mediated contraction. Strips from neonatal (1 d) and weanling (11 wk) rabbits were oriented to measure isometric tension in circular muscle. Bethanechol stimulated maximal tension in both age groups. Although the potencies for bethanechol were similar (ED50 approximately 5 microM), the maximal response was nearly 4-fold greater in weanling (1140 +/- 73 mN/cm2) versus neonate (305 +/- 54 mN/cm2), p less than 0.001. Maximum stress increased with age for bethanechol, high extracellular K+, and substance P, but not for serotonin, cholecystokinin octapeptide, neurotensin, or bombesin. Only bombesin stimulated larger contraction in neonates (152 +/- 37 mN/cm2) versus weanlings (86 +/- 20 mN/cm2), p less than 0.05. Potencies did not change with age, except for substance P and serotonin. Substance P and serotonin induced early phasic and prolonged tonic contractions, which were unaffected by tetrodotoxin or atropine. ED50 for the phasic and tonic components of substance P-stimulated contraction in neonates were 1.8 and 7.7 nM. Substance P was 60-70 times more potent in neonates versus weanlings (p less than 0.001). ED50 for serotonin-stimulated contraction in neonates (33 and 22 nM, respectively) were 20-30 times more potent than in weanlings (p less than 0.05). Motilin, morphine, epidermal growth factor, and gastrin did not stimulate contraction at either age. We conclude that age-dependent changes in agonist potency and efficacy may be one factor to explain in part the changes that occur in gastric motility during postnatal development.

The effect of methylcellulose on symptoms of constipation

The efficacy of methylcellulose was evaluated in 538 patients with a history of constipation. The patients were seen both by primary care physicians and by consultants. Patients were selected on the basis of passage of fewer than three stools per week. Frequency, consistency, and ease of passage of the stools were measured before and after one to three tablespoonsful per day of methylcellulose. The frequency of bowel movements as well as the consistency and ease of passage of the stools returned to normal with methylcellulose treatment; 61% of the patients were judged to have less constipation. The response to methylcellulose was not altered by the sex or age of the patients nor by the presence of colonic diverticular disease. This study suggests that methylcellulose is beneficial for the treatment of chronic and acute constipation.

Development of calcium channels in gastric smooth muscle

We used [3H]nitrendipine to characterize dihydropyridine sensitive calcium channels on cells isolated from neonatal (1 d) and weanling (11 wk) rabbit gastric fundic and antral smooth muscle. Incubating with and without nifedipine 20 microM, specific binding was 56 +/- 4% of total binding at 0.1 nM [3H]nitrendipine. Specific binding was saturable, reversible, achieved equilibrium by 10 min at 4 degrees C, and was linearly related to cell concentration. The affinity constant for [3H]nitrendipine was higher in weanling fundus (kd = 243 +/- 121 pM) versus antrum (kd = 771 +/- 190 pM), p less than 0.05. There were no age-related changes in affinity. In the antrum, the number of binding sites (Bmax) increased from 6,000 +/- 266/cell in neonates to 27,500 +/- 8,440/cell in weanlings (p less than 0.05). In the fundus Bmax was 7,750 +/- 2,100/cell in neonates, and there was no age-related change. To assess function, we compared isometric stress in full thickness muscle strips oriented to the circular layer. Bethanechol stimulated dose-dependent tonic contractions in the fundus and phasic contractions in the antrum. Maximal stress increased with age from 305 +/- 54 mN/cm2 to 1140 +/- 73 mN/cm2 (p less than 0.05) in the fundus and from 72 +/- 20 mN/cm2 to 154 +/- 30 mN/cm2 (p less than 0.05) in the antrum. Preincubation and incubation without calcium resulted in reversible inhibition of contraction at both ages. Nifedipine 10-microM inhibited 100% of bethanechol-stimulated contraction in the antrum, but only 25% in the fundus at both ages.(ABSTRACT TRUNCATED AT 250 WORDS)

Differences in the response of proximal and distal rabbit colonic muscle after electrical field stimulation

Electrical field stimulation (EFS) was performed on rabbit proximal and distal circular colonic smooth muscle to study the mechanisms of neural control of the colon. Electrical pulses were applied with parallel silver plate electrodes to muscle that had been stretched to Lo. The proximal muscle demonstrated an on-contraction during EFS. In distal muscle, EFS initiated an on-relaxation, followed by an on-contraction and an off-contraction. The time delay for the on-contraction of distal muscle was longer by 2.5 +/- 0.5 s than was the delay in proximal muscle (p less than 0.02). The amplitudes of the on- and off-contraction were dependent on the frequency of the EFS. The on- and off-responses were completely inhibited by 3 x 10(-6) M tetrodotoxin. Atropine inhibited the distal on-contraction at all EFS frequencies and the proximal on-response at EFS frequencies less than 16 Hz. Atropine had a partial inhibitory effect on the distal off-response (approximately 30%). Bombesin and substance P were released during prolonged EFS. Desensitization of the distal colonic muscle to bombesin did not affect the distal off-contraction. However, desensitization of the tissue to substance P and exposure to substance P antagonists inhibited the distal off-contraction. These studies suggest that (a) acetylcholine mediates the on-contraction of the distal circular colonic muscle, and a major part of the on-contraction for the proximal muscle, and (b) substance P is responsible for the off-contraction of the distal muscle.

Involvement of substance P in noncholinergic excitation of rabbit colonic muscle

Neurokinins have been implicated as noncholinergic excitatory neurotransmitters in the mammalian gastrointestinal tract. To characterize the myogenic and neurogenic response of colonic muscle to neurokinins we studied the mechanical response of muscle strips from proximal and distal colon and the release of [3H]acetylcholine in response to substance P (SP), neurokinin A (NKA) and neurokinin B (NKB). All neurokinins caused a dose-dependent inotropic response. SP was 80 times more potent in distal compared with proximal longitudinal muscle. The rank order of potencies in proximal longitudinal muscle was NKA greater than SP = NKB and in distal muscle NKA = SP = NKB. Desensitization to SP or pretreatment with a SP antagonist inhibited the mechanical response to SP and the atropine-resistant inotropic off response to electrical stimulation. Only longitudinal muscle from distal colon had an atropine- and hexamethonium-sensitive inotropic component to SP. In contrast, all three peptides were equipotent in releasing [3H]acetylcholine from longitudinal muscle strips preincubated with [3H]choline. These results suggest the following: 1) SP is a potent agonist of rabbit colon with a proximal distal gradient in biological potency; 2) the myogenic response of the distal colon appears to be mediated through a NK-1 receptor; and 3) SP is a major mediator of the noncholinergic component of the off response in distal longitudinal muscle.

Effect of prostaglandin E2 on rabbit colonic smooth muscle cell contraction

Isolated circular smooth muscle cells from the rabbit distal colon were used to study the effect of prostaglandin E2 (PGE2) on bethanechol-stimulated smooth muscle cell contraction. Contraction was expressed as the percentage decrease in mean cell length compared with unstimulated cells. Incubation with different concentrations of PGE2 (10(-10)-10(-6) M) did not cause contraction or relaxation of unstimulated smooth muscle cells. Bethanechol stimulated a dose-dependent contraction that was maximal at 30 s. The threshold for bethanechol-stimulated contraction was 10(-11) M; the ED50 was 10(-10) M; and the maximum contraction (23.0 +/- 1.8%) occurred at 10(-8) M. Preincubation with PGE2 reduced both the efficacy and potency of bethanechol-stimulated contraction. Preincubation with 8-bromoadenosine 3',5'-cyclic monophosphate (8-BrcAMP) or dibutyryl-cAMP reduced the efficacy of bethanechol-stimulated contraction without affecting potency. Increasing concentrations of PGE2 stimulated a dose-dependent increase in the production of intracellular cAMP (P less than 0.05). These studies show that PGE2 inhibits bethanechol-stimulated contraction of isolated colonic circular myocytes and is associated with increased production of intracellular cAMP. There is also a cAMP-independent effect of PGE2 on the potency of bethanechol stimulation.

Characterization of the effects of neurokinins on canine antral muscle

The excitation of longitudinal antral muscle by substance P (SP) involves both a myogenic and a cholinergic effect. To examine if these responses are mediated by different neurokinin receptors, we studied the mechanical response and the release of [3H]acetylcholine from antral muscle strips in response to SP, substance P methylester (SPME), neurokinin A (NKA), neurokinin B (NKB), and several non-mammalian tachykinins. All peptides studied showed a dose-dependent inotropic and chronotropic effect on spontaneous phasic contractions. This ionotropic effect in longitudinal muscle was partially atropine sensitive for SPME, SP, and NKB but not for NKA, whereas neither atropine nor tetrodotoxin had an effect in circular muscle. In longitudinal muscle, all three neurokinins were equipotent. In longitudinal muscle treated with atropine and in circular muscle, the rank order of potency for the inotropic response was NKA greater than NKB greater than SP greater than SPME. For the chronotropic response the rank order was SPME, SP greater than NKA greater than NKB. NKA, NKB, and SP caused a dose-dependent, tetrodotoxin-sensitive increase in [3H]acetylcholine release from strips preincubated with [3H]choline. NKA was significantly more potent to release [3H]acetylcholine than either NKB or SP. The stimulated release was inhibited by [D-Ala2,D-Met5]methionine enkephalinamide and the SP antagonist, spantide. These results are consistent with the hypothesis that NKA is the natural ligand mediating the myogenic inotropic response in both muscle layers and the cholinergic response in longitudinal muscle.

Choledochal fungal ball. An unusual cause of biliary obstruction

A 31-year-old patient with sickle-cell disease who had previous cholecystectomy developed acute onset of jaundice and abdominal pain. An endoscopic retrograde cholangiography demonstrated multiple filling defects within the bile ducts. Microscopic examination of "calculi" removed at surgery revealed that a fungal ball composed of Candida was the cause of biliary obstruction in this case. The patient eventually recovered after removal of the fungal masses and intrabiliary instillation of amphotericin.

Cultured circular smooth muscle from the rabbit colon

Although cultured vascular smooth muscle cells have been extensively characterized and investigated, there are very few studies of cultured intestinal smooth muscle cells. The aim of this study was to culture colonic smooth muscle (CSM) cells from the rabbit colon. Freshly isolated CSM cells from the circular muscle layer of the distal colon were prepared by collagenase digestion. In primary culture, CSM cells attached to the culture vessels by 48 to 72 h, proliferated by 3 to 7 d, and reached confluency by 14 to 17 d with a "hill-and-valley" pattern. Spontaneous contractions were not observed at any time at 21 degrees or 37 degrees C. Confluent primary cultures were greater than 95% CSM cells, as identified by intensely positive immunofluorescent staining to smooth muscle actin-specific CGA7 and muscle-specific HHF-35 monoclonal antibodies. Transmission electron microscopy of freshly isolated and proliferating CSM cells revealed ultrastructural features consistent with smooth muscle cells. We successfully cultured CSM cells of the rabbit from freshly isolated cells and validated these CSM cells by electron microscopy and immunocytochemical staining. These highly pure primary cultures may be used to investigate numerous aspects of CSM cell metabolism and physiology.

Sources of calcium for contraction of distal circular muscle or taenia coli in the rabbit

Studies were performed on proximal taenia coli and distal circular muscle from the rabbit to determine if the source of Ca2+ required for bethanechol stimulation of contraction was similar after permeabilizing the tissues with saponin. The EC50 for Ca2+ stimulation of contraction was pCa 6.1 +/- 0.1 for both tissues. The peak response occurred at pCa 4.5. The addition of 1 microM calmodulin did not alter the Ca2+ EC50 or the peak response. Caffeine (20 mM) stimulated contraction of both taenia coli and distal circular muscle. The caffeine-stimulated contractile response was threefold greater in the taenia than in the distal circular muscle (P less than 0.05). Perfusion of thin strips of colonic muscle with buffer, containing 10(-7) M Ca2+, reduced the amplitude of bethanechol-stimulated contraction. The perfusion time to reduce the contraction by 50% was greater in the proximal muscle (2.4 +/- 0.1 min) than in the distal muscle (1.1 +/- 0.5 min) (P less than 0.001). These data suggest that 1) the intracellular Ca2+ concentration necessary for contraction is similar in the proximal and distal colon and 2) the intracellular Ca2+ stores appear to be greater in proximal taenia coli compared with distal circular muscle.

Development of the muscarinic receptor in rabbit gastric smooth muscle

We used binding of [N-methyl-3H]scopolamine ( [3H]-NMS) to tissue homogenates and isometric contraction of muscle strips to characterize perinatal changes in the muscarinic receptor on rabbit gastric smooth muscle. In homogenates from fetal (28 days of gestation), 1-, 3-, and 7-day, 4- and 11-wk-old rabbits, specific binding was saturable and temperature dependent, achieved equilibrium by 10 min at 30 degrees C, and was linearly related to tissue concentration. Specific binding was 80 +/- 2% of total binding at 0.2 nM [3H]NMS. The number of binding sites was 120,000 receptors/cell, maximal during the first week of life compared with the fetus or older animals. Affinity of [3H]NMS was highest in the first week of life (Kd = 345 +/- 24 pM, 1 day old). Age did not affect Hill coefficients or Ki values; secoverine and 4-diphenylacetoxy-N-methylpiperidine methiodide were 50-fold more potent than pirenzepine. In muscle strips, bethanechol stimulated dose-dependent atropine-inhibitable isometric contraction. The doses required for half-maximal contraction were similar in both age groups (5-6 microM), but maximal contraction was fivefold greater in weanlings compared with neonates. Increasing extracellular potassium concentration resulted in similar differences, suggesting that the differences were not receptor related. These results suggest that well-differentiated M2-muscarinic receptors are functional on rabbit gastric smooth muscle during the perinatal period.

Role of inflammatory mediators in colonic smooth muscle function in ulcerative colitis

Patients with ulcerative colitis have a decrease in colonic motility which may increase their diarrheal symptoms. Studies in patients with ulcerative colitis showed that the postprandial spike response was slightly decreased and the intraluminal pressure response was absent. In vitro studies showed that the circular smooth muscle, obtained from patients with ulcerative colitis or from a rabbit model of experimental colitis, generated decreased force compared to muscle not associated with mucosal inflammation. The decrease in muscle contraction was observed with bethanechol stimulation or electrical field stimulation. Since the response to an increased extracellular concentration of potassium [( K+]0) was also diminished, the decreased response appears to be caused by an abnormality in the intrinsic contractile mechanism of colonic smooth muscle. Further studies are necessary to determine if metabolic abnormalities are present in the colonic muscle in patients with colitis.

[3H]QNB binding and contraction of rabbit colonic smooth muscle cells

We used radioligand binding and studies of cell contraction to characterize muscarinic receptors on dispersed smooth muscle cells from rabbit proximal and distal colon. Cells obtained after serial incubations in collagenase were used to measure binding of tritiated quinuclidinyl benzilate [( 3H]QNB). AT 37 degrees C, specific [3H]QNB binding was saturable and linearly related to cell number. Nonlinear regression analysis was used to determine the affinity of [3H]QNB for its receptor. In the distal colon the Kd was 60 pM, and the mean number of receptors was 1.2 X 10(6)/cell. Compared with cells from the distal colon, cells from the proximal colon had a lower affinity (Kd = 337 pM) but similar numbers of receptors. The concentrations of the antagonists atropine, secovorine, and pirenzepine, which were required for inhibition of 50% [3H]QNB binding (IC50), were 8, 5, and 870 nM, respectively, suggesting that the receptors are of the M2-muscarinic subclass. Hill coefficients for these agents were 1.1, 0.9, and 1.1, suggesting binding to a single receptor. The IC50 for the muscarinic agonists bethanechol and oxotremorine were 80 and 0.57 microM, respectively. Hill coefficients were 0.67 for both, suggesting more complex interactions involving receptors of different affinities. In studies of cell contraction, bethanechol stimulated a dose-dependent decrease in cell length with half the maximal contraction occurring at 100 pM. These results suggest that 1) contraction is mediated by binding of bethanechol to M2-muscarinic receptors and that 2) there are a large number of spare receptors in colonic smooth muscle.