Asymmetrical, agonist-induced fluctuations in local extracellular [Ca(2+)] in intact polarized epithelia.

We recently proposed that extracellular Ca(2+) ions participate in a novel form of intercellular communication involving the extracellular Ca(2+)-sensing receptor (CaR). Here, using Ca(2+)-selective microelectrodes, we directly measured the profile of agonist-induced [Ca(2+)]ext changes in restricted domains near the basolateral or luminal membranes of polarized gastric acid-secreting cells. The Ca(2+)-mobilizing agonist carbachol elicited a transient, La(3+)-sensitive decrease in basolateral [Ca(2+)] (average approximately 250 microM, but as large as 530 microM). Conversely, carbachol evoked an HgCl2-sensitive increase in [Ca(2+)] (average approximately 400 microM, but as large as 520 microM) in the lumen of single gastric glands. Both responses were significantly reduced by pre-treatment with sarco-endoplasmic reticulum Ca(2+) ATPase (SERCA) pump inhibitors or with the intracellular Ca(2+) chelator BAPTA-AM. Immunofluorescence experiments demonstrated an asymmetric localization of plasma membrane Ca(2+) ATPase (PMCA), which appeared to be partially co-localized with CaR and the gastric H(+)/K(+)-ATPase in the apical membrane of the acid-secreting cells. Our data indicate that agonist stimulation results in local fluctuations in [Ca(2+)]ext that would be sufficient to modulate the activity of the CaR on neighboring cells.

Effect of growth hormone on intestinal Na+/glucose cotransporter activity.

BACKGROUND: Growth hormone (GH) has been used alone or as part of a defined regimen in the treatment of patients with short bowel syndrome; however its mode of action remains unclear. Growth hormone has been shown to increase amino acid, water, and electrolyte absorption from the small intestine. The acute effect of growth hormone on intestinal sugar transport has not been described previously. METHODS: Mucosal preparations of rat jejunum were mounted in the Ussing chamber. Growth hormone (2 x 10(-6) M or 8 x 10(-6) M) or vehicle was added to the serosal chamber 1, 3, or 5 hours later. Twenty or 40 minutes after growth hormone addition, 30 mmol/L 3-O-methylglucose was added to both chambers, and the change in short-circuit current (deltaIsc) was recorded. In separate experiments, tissues were pretreated with phloridzin, an inhibitor of Na+/glucose cotransport, before the addition of 3-O-methylglucose. In the final set of experiments, kinetic studies were performed. RESULTS: GH did not induce any alterations in baseline electrical parameters. Only tissues left in the chambers for 5 hours, but not 1 or 3 hours, before GH treatment displayed a greater 3-O-methylglucose-induced deltaIsc than controls (p < .05). The increase in Isc induced by 3-O-methylglucose was 100% phloridzin-inhibitable. Kinetic analysis showed that growth hormone administration is associated with an increase in Na+/glucose cotransporter maximal velocity (Vmax) but no significant change in carrier affinity for substrate (Km). CONCLUSIONS: Growth hormone increases intestinal sugar transport, but only in tissue that has not been exposed to endogenous GH for over 3 hours.

Luminal osmolarity downregulates gene expression of Na+/H+ exchanger (NHE3) in rat colon mucosa.

Water-coupled Na&sup+ absorption in the colon is mediated principally by Na+/H+ exchange (isoforms NHE2 and NHE3). To determine whether luminal ion composition or osmolarity influences NHE expression in colon mucosa, two groups (n = 6 in each) of adult male Sprague-Dawley rats underwent sham laparotomy or loop ileostomy. In these studies, diversion did not markedly alter mRNA levels for NHE2, NHE3, or Na+/K+, at 8 or 21 days, indicating that loss of luminal volume does not alter NHE gene expression. To evaluate the effects of specific luminal components, we infused equal volumes of half-normal (154 mOsm) or iso-osmolar (308 mOsm) solutions of saline and mannitol into the diverted colon. All solutions elicited significant (45% to 60%; P <0.05) decreases in mRNA levels for NHE3, with iso-osmolar mannitol eliciting the greatest changes. Decreases in NHE2 and Na+/K+ mRNA levels were observed following these infusions but were not as marked as the changes for NHE3. These findings suggest that (1) loss of luminal Na+ is not, in itself, a signal that regulates NHE expression and (2) infusion of any solute, including Na+ itself, provides a signal to downregulate expression of NHE3 in colon mucosa.

Intercellular communication mediated by the extracellular calcium-sensing receptor.

Agonist-evoked, intracellular Ca2+-signalling events are associated with active extrusion of Ca2+ across the plasma membrane, implying a local increase in Ca2+ concentration ([Ca2+]) at the extracellular face of the cell. The possibility that these external [Ca2+] changes may have specific physiological functions has received little consideration in the past. Here we show that, at physiological ambient [Ca2+], Ca2+ mobilization in one cell produces an extracellular signal that can be detected in nearby cells expressing the extracellular Ca2+-sensing receptor (CaR), a cell-surface receptor for divalent cations with a widespread tissue distribution. The CaR may therefore mediate a universal form of intercellular communication that allows cells to be informed of the Ca2+-signalling status of their neighbours.

Diversion colitis in patients with myelopathy: clinical, endoscopic, and histopathological findings.

OBJECTIVE: One of the problems with a diverting colostomy, applied in patients with myelopathy for complications of the neuropathic large bowel, is diversion colitis. A clinical, endoscopic, and histological survey was conducted to describe the problem in these patients. METHODS: 19 patients with myelopathy who have had colostomies (68% of those available) participated in the survey. History of rectal discharge and perineal ulceration plus colonoscopic and biopsy observations were recorded. 20 patients with myelopathy who have not had colostomies, with clinically indicated colonoscopic examinations, were compared for skin breakdown and endoscopic appearance. RESULTS: 15 patients who had colostomies (79%) reported rectal discharge, and 9 (47%) sustained perineal ulceration, 2 being recurrent and refractory. None of the 20 patients who had not had colostomies had perineal ulceration (p = 0.04). Colonoscopy revealed mucosal erythema and friability in 18 patients (94%) with a predominance in the rectosigmoid colon. 1 of 20 without colostomy presented with this picture (p < 0.001). Mucosal biopsies of diverted colon revealed chronic inflammation in all patients, severe inflammation in 13 of 19 subjects at < or = 20 cm from the anus, and in 3 of 10 at > 20 cm (p = 0.06). No difference in the severity of inflammation with time, 0 to 2 years versus > 2 to 18 years post colostomy, could be demonstrated. CONCLUSIONS: Diversion colitis is a frequent, persistent, and sometimes problematic complication in patients with myelopathy who have also had colostomies.

Symptomatic gallstones in patients with spinal cord injury.

Patients with spinal cord injury (SCI) have an increased prevalence of cholelithiasis. The goal of this study was to clarify the presentation and management of symptomatic gallstone disease in patients with SCI. We performed a retrospective study of presentation of gallstone complications in patients with SCI who underwent cholecystectomy for complications of gallstone disease. The West Roxbury Veterans Administration Medical Center SCI registry (605 patients) was searched for patients who had undergone cholecystectomy more than 1 year after SCI (35 patients). Gallbladder disease profiles for the 35 patients undergoing cholecystectomy for complications of gallstone disease were prepared, including demographics, clinical presentation, diagnostic studies, operative and pathologic findings, and postoperative complications. All patients were white. Thirty-four were male and the mean age was 50 years (range 35 to 65 years). The majority of patients (66%) complained of right upper quadrant abdominal pain, even those patients with SCI at high (i.e., cervical) levels. Of the 35 patients in our study group, 22 (63%) had biliary colic and chronic cholecystitis, nine (26%) had acute cholecystitis (gangrenous cholecystitis in two), two (6%) had choledocholithiasis symptoms or cholangitis, and two (6%) had gallstone pancreatitis. Major perioperative morbidity occurred in two (6%) of the 35 patients (pulmonary embolus; intraoperative hemorrhage), and there were no deaths. In the great majority of patients with SCI, cholelithiasis presents with chronic pain and not with life-threatening complications. Our findings suggest that presentation is no more acute in patients with SCI than in the general population. Characteristic symptoms and signs are not necessarily obscured by SCI injury, regardless of the level.

Relation of surgical volume to outcome in eight common operations: results from the VA National Surgical Quality Improvement Program.

OBJECTIVE: To examine, in the Veterans Health Administration (VHA), the relation between surgical volume and outcome in eight commonly performed operations of intermediate complexity. SUMMARY BACKGROUND DATA: In multihospital health care systems such as VHA, consideration is often given to closing low-volume surgical services, with the assumption that better surgical outcomes are achieved in hospitals with larger surgical volumes. Literature data to support this assumption in intermediate-complexity operations are either limited or controversial. METHODS: The VHA National Surgical Quality Improvement Program data on nonruptured abdominal aortic aneurysmectomy, vascular infrainguinal reconstruction, carotid endarterectomy (CEA), lung lobectomy/pneumonectomy, open and laparoscopic cholecystectomy, partial colectomy, and total hip arthroplasty were used. Pearson correlation, analysis of variance, mixed effects hierarchical logistic regression, and automatic interaction detection analysis were used to assess the association of annual procedure/specialty volume with risk-adjusted 30-day death (and stroke in CEA). RESULTS: Eight major surgical procedures (68,631 operations) were analyzed. No statistically significant associations between procedure or specialty volume and 30-day mortality rate (or 30-day stroke rate in CEA) were found. CONCLUSIONS: In VHA hospitals, the procedure and surgical specialty volume in eight prevalent operations of intermediate complexity are not associated with risk-adjusted 30-day mortality rate from these operations, or with the risk-adjusted 30-day stroke rate from CEA. Volume of surgery in these operations should not be used as a surrogate for quality of surgical care.

Selective decreases in levels of mRNA encoding a water channel (AQP3) in ileal mucosa after ileostomy in the rat.

Water channels (aquaporins) provide pathways for water permeation in a variety of epithelia. Aquaporin-3 (AQP3) has been localized to the basolateral membranes of epithelial cells in the small intestine, but mechanisms that regulate its expression and function have not been explored. To determine whether luminal content may influence intestinal AQP3 gene expression, adult Sprague-Dawley rats underwent sham laparotomy (N = 11) or loop ileostomy (N = 9) and were killed 8 days after procedures. Northern blot analysis was used to measure messenger RNA (mRNA) levels for AQP3 and the Na(+)/K(+) ATPase, a housekeeping transporter that regulates cellular levels of Na(+) and K(+). At sacrifice, histologic examination revealed only minimal changes in mucosal morphology. In sham animals, Na/K mRNA levels increased moderately in distal regions of the small intestine. Ileostomy did not alter these levels in any region. In contrast, in sham animals, AQP3 mRNA levels increased along the length of the intestine and were markedly higher in the distal ileum. Diversion of luminal contents decreased AQP3 mRNA levels in the postileostomy region by 30% to 50%. These findings indicate regional variations in expression of the AQP3 water channel in mucosa of the small intestine. In addition, they suggest that AQP3 gene expression may depend on the presence of luminal contents.

Gastrin-mediated effects of omeprazole on rat colon mucosa.

BACKGROUND: Omeprazole increases circulating gastrin levels, which in turn may affect the growth and differentiation of colon mucosa. Chloride transport mechanisms in normal colon were analyzed as markers for possible trophic actions of endogenous hypergastrinemia. METHODS: Four groups of Fischer rats were studied for 10 days. Group 1 (baseline) received no treatment. Group 2 received omeprazole only. Group 3 received omeprazole plus vehicle. Group 4 received omeprazole plus CCK-B gastrin receptor antagonist (GRA) L740,093 in vehicle. On day 10 serum gastrin was assayed. Colon mucosa was analyzed for protein and DNA content. Semiquantitative Northern analysis measured levels of messenger RNA (mRNA) encoding for key Cl- transporters: Na-K-Cl cotransporter (Cl- secretion in crypts), Cl-/HCO3- exchanger (Cl- absorption in villi), and Na/K adenosine triphosphatase (not directly involved in Cl- transport). RESULTS: Omeprazole increased gastrin levels, which were not altered by vehicle or GRA. Omeprazole increased protein, DNA, and Na/K adenosine triphosphatase mRNA levels, with no effect by GRA. In contrast, omeprazole decreased Na-K-Cl and Cl-/HCO3- mRNA levels, effects that were partly reversed by GRA. CONCLUSIONS: Omeprazole augments growth index values of colon mucosa independent of serum gastrin. Against a background of omeprazole-induced achlorhydria hypergastrinemia appears to influence differentiation rather than growth of normal colon mucosa.

Expression of an extracellular calcium-sensing receptor in rat stomach.

BACKGROUND & AIMS: Circulating levels of Ca2+ can influence secretory functions and myoelectrical properties of the stomach. A Ca2+-sensing receptor (CaR) has recently been identified in tissues that regulate systemic Ca2+ homeostasis. The aim of this study was to evaluate expression of CaR in the stomach of the rat. METHODS: In forestomach and glandular stomach, reverse-transcription polymerase chain reaction was used to amplify a 380-base pair product, which is 99% homologous with transcripts obtained in parathyroid and kidney. RESULTS: Northern analysis of gastric mucosal polyA+ RNA revealed 7. 5- and 4.1-kilobase transcripts, similar to those obtained in rat parathyroid and kidney. Immunohistochemistry revealed CaR expression in regions of the submucosal plexus and myenteric neurons. In sections of intact tissue, preparations of primary culture surface cells and surgically dissected gastric glands, staining was observed consistently in epithelial cells of the gastric glands and in gastric surface cells. In parietal cells in isolated gastric glands, intracellular levels of Ca2+ responded to conditions that are known to activate CaR. CONCLUSIONS: These are the first reported observations that CaR is expressed in different epithelial cells of mammalian gastric mucosa and its enteric nerve regions. The effects of extracellular Ca2+ on gastric function may be attributable to activation of CaR.

Selective increase in gastric mucosal mRNA encoding basolateral Na-K-2C1 cotransporter following ileostomy in the rat.

Results of previous studies suggest that major surgical resections or reconstructions of the distal small intestine can alter morphologic and functional properties of the stomach. Little is known about the effect of lesser surgical alterations such as construction of an ileostomy, on the morphology and transport properties of the gastric mucosa. To evaluate the effects of ileostomy, Sprague-Dawley rats underwent sham laparotomy (n = 10) or loop ileostomy construction (n = 10). After body weights had stabilized ( approximately 21 days) the animals were killed. Gastric mucosal scrapings were prepared for Northern blot analysis of messenger RNA levels for (1) H/K ATPase, found in parietal cells; (2) Na-K-2C1 cotransporter, found in both parietal and surface cells; and (3)Na/K ATPase, found in all gastric mucosal cells. Gastric mucosa from ileostomy animals was visibly hypertrophied compared to sham-operated animals. There was a 145% increase in the mRNA levels of the Na-K-2Cl cotransporter in gastric mucosa of the ileostomy group but no significant changes in H/K ATPase or Na/K ATPase mRNA levels. Construction of an ileostomy selectively enhances expression of the Na-K-C1 cotransporter in the gastric mucosa. Further studies are required to understand the neurohumoral stimuli underlying this selective response.

Broncholithiasis and thoracoabdominal actinomycosis from dropped gallstones.

We report a case of successfully managed invasive, thoracoabdominal actinomycosis caused by the intraperitoneal spillage of gallstones during laparoscopic cholecystectomy. The infected gallstones traversed the diaphragm, migrated into the lung parenchyma, and obstructed a segmental bronchus, causing pneumonia. Treatment involved retrieval of the obstructing stone, debridement and drainage of the pleuroperitoneal phlegmon/abscess, and intravenous antibiotics. The case illustrates the need to remove gallstones at the time of cholecystectomy.