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PubMed1994

Effects of the agents affecting cyclic nucleotide metabolism on the bradykinin- and des-Arg9-bradykinin-induced relaxations and contractions in isolated rat duodenum.

1. Bradykinin and related kinins possess two different types of action (consisting of relaxation and contraction) in the isolated rat duodenum via their specific receptors. However, the mechanisms of these actions have not been fully elucidated. The present study was undertaken to investigate the effects of the agents affecting cyclic nucleotide metabolism on bradykinin-induced relaxations and on bradykinin- and des-Arg9-bradykinin-induced contractions. 2. Des-Arg9-bradykinin, B1 receptor agonist, and high concentrations of bradykinin elicited dose-dependent contractile responses in the rat duodenum, while low concentrations of bradykinin caused a dose-dependent relaxation in this tissue. 3. Nicotinic acid, an inhibitor of adenylate cyclase, inhibited the relaxation of rat duodenum induced by bradykinin at low concentrations in a non-competitive manner. However, the inhibitory efficacy of nicotinic acid against bradykinin was limited by 39.9% and this inhibition was not further increased by higher concentrations of nicotinic acid up to 10(-3) M. 4. Imidazole, an activator of cyclic nucleotide phosphodiesterase, caused a slight inhibition of the relaxant responses to low concentrations of bradykinin and of the contractile responses to des-Arg9-bradykinin and high concentrations of bradykinin in isolated rat duodenum. These inhibitions were also limited in efficacies and not increased by higher concentrations of imidazole. 5. Methylene blue, an agent that inhibits soluble guanylate cyclase, suppressed the contractions of rat duodenum induced by des-Arg9-bradykinin and high concentrations of bradykinin in a non-competitive manner. Again, these inhibitions were limited and further increase in the inhibitory efficacy was not observed in spite of increasing the methylene blue concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed2005

Nuclear receptor and target gene mRNA abundance in duodenum and colon of dogs with chronic enteropathies.

Nuclear receptors (NR), such as constitutive androstane receptor (CAR), pregnane X receptor (PXR) and peroxisome proliferator-associated receptors alpha and gamma (PPARalpha, PPARgamma) are mediators of inflammation and may be involved in inflammatory bowel disease (IBD) and food responsive diarrhea (FRD) of dogs. The present study compared mRNA abundance of NR and NR target genes [multi drug-resistance gene-1 (MDR1), multiple drug-resistance-associated proteins (MRD2, MRD3), cytochrome P450 (CYP3A12), phenol-sulfating phenol sulfotransferase (SULT1A1) and glutathione-S-transferase (GST A3-3)] in biopsies obtained from duodenum and colon of dogs with IBD and FRD and healthy control dogs (CON; n=7 per group). Upon first presentation of dogs, mRNA levels of PPARalpha, PPARgamma, CAR, PXR and RXRalpha in duodenum as well as PPARgamma, CAR, PXR and RXRalpha in colon were not different among groups (P>0.10). Although mRNA abundance of PPARalpha in colon of dogs with FRD was similar in both IBD and CON (P>0.10), PPARalpha mRNA abundance was higher in IBD than CON (P<0.05). Levels of mRNA of MDR1 in duodenum were higher in FRD than IBD (P<0.05) or CON (P<0.001). Compared with CON, abundances of mRNA for MRP2, CYP3A12 and SULT1A1 were higher in both FRD and IBD than CON (P<0.05). Differences in mRNA levels of PPARalpha and MRP2 in colon and MDR1, MRP2, CYP3A12 and SULT1A1 in duodenum may be indicative for enteropathy in FRD and (or) IBD dogs relative to healthy dogs. More importantly, increased expression of MDR1 in FRD relative to IBD in duodenum may be a useful diagnostic marker to distinguish dogs with FRD from dogs with IBD.

Animals↗

PubMed2006

Loss of extracellular E-cadherin in the normal mucosa of duodenum and colon of patients with familial adenomatous polyposis.

The duodenum is the main site for (pre-) malignant extracolonic manifestations in patients with familial adenomatous polyposis (FAP). Changes in the E-cadherin/beta-catenin complex play a pivotal role in the development of malignancies. Loss of E-cadherin has been described in association with loss of SMAD4. To elucidate the pathways leading to the development of duodenal adenomas in patients with FAP, the distributions of E-cadherin, SMAD4, and beta-catenin were analyzed. Furthermore, differences between the duodenum and colon were evaluated. Normal FAP duodenum (n = 13) and FAP duodenal adenomas (n = 50; total, 21 patients) were compared with non-FAP duodenal adenomas (n = 7) and normal non-FAP duodenum (n = 15) by immunohistochemical staining for extracellular and intracellular E-cadherin, beta-catenin, and SMAD4. Colonic biopsies of 10 patients with FAP were also studied, as well as non-FAP colonic adenomas (n = 26) and non-FAP normal colon (n = 12). Compared with the intracellular component of E-cadherin that was present in all cases, a significant loss of extracellular E-cadherin was observed in both duodenal and colonic adenomas and normal tissue of patients with FAP. Nuclear localization of beta-catenin was more often observed in duodenal FAP adenomas compared with non-FAP adenomas. Loss of nuclear SMAD4 was seen in the duodenum and, to a higher degree, in the colon of patients with FAP, as well as non-FAP patients. The loss of extracellular E-cadherin in the normal duodenal and colonic mucosa of patients with FAP might play a role in the high susceptibility of these tissues for (pre-) malignant transformation.

Adenoma↗

PubMed2005

Central vagal stimulation activates enteric cholinergic neurons in the stomach and VIP neurons in the duodenum in conscious rats.

The influence of central vagal stimulation induced by 2h cold exposure or intracisternal injection of thyrotropin-releasing hormone (TRH) analog, RX-77368, on gastro-duodenal enteric cholinergic neuronal activity was assessed in conscious rats with Fos and peripheral choline acetyltransferase (pChAT) immunoreactivity (IR). pChAT-IR was detected in 68%, 70% and 73% of corpus, antrum and duodenum submucosal neurons, respectively, and in 65% of gastric and 46% of duodenal myenteric neurons. Cold and RX-77368 induced Fos-IR in over 90% of gastric submucosal and myenteric neurons, while in duodenum only 25-27% of submucosal and 50-51% myenteric duodenal neurons were Fos positive. In the stomach, cold induced Fos-IR in 93% of submucosal and 97% of myenteric pChAT-IR neurons, while in the duodenum only 7% submucosal and 5% myenteric pChAT-IR neurons were Fos positive. In the duodenum, cold induced Fos in 91% of submucosal and 99% of myenteric VIP-IR neurons. RX-77368 induces similar percentages of Fos/pChAT-IR and Fos/VIP-IR neurons. These results indicate that increased central vagal outflow activates cholinergic neurons in the stomach while in the duodenum, VIP neurons are preferentially stimulated.

Animals↗

PubMed2006

The pancreatic polypeptide family and the migrating motor complex of the rat: differential effects in the duodenum and jejunum.

AIM: To investigate the effects of members of the pancreatic polypeptide family on migrating myoelectric complexes in rats in vivo. METHODS: Rats were supplied with bipolar electrodes at 5 (duodenum), 15 and 25 cm (jejunum) distal to pylorus for electromyography. The natural ligands neuropeptide Y, pancreatic polypeptide, peptide YY1-36 and peptide YY3-36 were infused IV at doses of 0.5-400 pmol kg(-1) min(-1). The mechanisms of action were studied after pre-treatment with N(omega)-nitro-L-arginine (L-NNA) 1 mg kg(-1), guanethidine 3 mg kg(-1) and in bilaterally vagotomized animals. RESULTS: PP inhibited myoelectrical activity dose-dependently in both the duodenum (ED50 5.8 pmol kg(-1) min(-1)) and jejunum (2.6 pmol kg(-1) min(-1)). PYY1-36 and PYY3-36 also had inhibitory effect in the jejunum (4.4 and 130 pmol kg(-1) min(-1), respectively). PYY1-36 had no significant effect in the duodenum, whereas PYY3-36 stimulated myoelectrical activity at the highest doses. NPY was without effect. In the jejunum neither L-NNA, guanethidine or vagotomy had any significant influence on the inhibitory effects of PP, PYY1-36 and PYY3-36. In the duodenum, the effect of PP was inhibited by guanethidine, but not L-NNA or vagotomy. The stimulatory effect of PYY3-36 in the duodenum was blocked by L-NNA and vagotomy, whereas guanethidine was without effect. CONCLUSION: Peptides of the PP family modulate small bowel motility differentially. Whereas their general effect is inhibitory in the jejunum, the mixing duodenal compartment is stimulated by PYY3-36, suggested to reflect receptor distribution distinction in the gut. This implicates distribution of distinct receptors in the gut being activated by either peptide.

Animals↗

PubMed2006

Immune responses in Eimeria acervulina infected one-day-old broilers compared to amount of Eimeria in the duodenum, measured by real-time PCR.

T-cell responses are supposed to be the major immune reactions in broilers infected with Eimeria. The nature of such T-cell responses is influenced by the species of Eimeria involved, age of the host, amount of parasites and the preceding infection history. In young chicks the intestine is still developing in length while the lymphocyte populations in the gut develop and differentiate. In chicks infected at young age the immune response may be different in quality as compared to responses in adults. We investigated the (T-cell) immune responses of young broilers to a primary Eimeria acervulina infection in relation to the number of parasites used for infection. In our experiment we infected one-day-old broilers with a low (5 x 10(2) oocysts) and a high (5 x 10(4) oocysts) dose of E. acervulina. We used a newly developed species specific real-time PCR to quantify total amount of parasites in the duodenum as the number of oocysts in faeces may not be representative for the exposure of the gut immune system. We characterized T-cell subsets in the duodenum by means of FACS-analyses, lymphocyte proliferation assays with spleen lymphocytes and the mRNA profiles of different cytokines (TGF-beta2, -4, IFN-gamma, IL-2, -6, -8 and -18) in the duodenum by means of real-time PCR. From day 5 p.i. broilers with a high dose of E. acervulina had a significantly lower body weight than the control group. No increase in CD4(+) cells, but a strong increase in CD8(+) cells was observed at days 7 and 9 p.i. in the duodenum of broilers infected with a high dose E. acervulina. IL-8 mRNA responses were observed after infection with low and with high infection doses, but no IFN-gamma and TGF-beta mRNA responses were found in the duodenum. The specific proliferative T-cell responses to a low infectious dose were not significantly different as compared to the control group. In conclusion, based on the kinetics of observed responses a primary infection with a high dose of E. acervulina in one-day-old broilers seems to generate an immune response that shows a peak at the time of oocyst excretion, whereas the immune response to a low dose is less explicit.

Animals↗

PubMed2001

Age-associated changes in gene expression patterns in the duodenum and colon of rats.

In humans, decreased intestinal motility, compromised nutritional status and increased risk of colon cancer are commonly associated with aging. Here, we used the cDNA microarray analysis to detect age-associated changes in duodenal and colonic gene expression in male Fischer 344 rats. The primary finding of this study is that the magnitude and direction of age-associated changes in gene expression differs in the colon and duodenum. In the colon, 56 genes showed altered expression, whereas expression of only 25 genes was altered in the duodenum. The magnitude of change was greater in the colon than in the duodenum. The direction of change also differed; in the aged colon, expression of 51 genes increased and only five genes decreased. In contrast, in the aged duodenum, only seven genes increased, whereas 18 genes decreased in expression. In the duodenum of aged rats, expression of genes involved in ATP-generating pathways is decreased. In contrast, in the colon of aged rats, expression of genes involved in energy generating pathways and in lipid oxidation is increased. In addition, in the aging colon, an increased expression of genes that show an aberrant regulation in colon cancer, including CD44, ras, and maspin is observed. Collectively, these findings provide clues to molecular events that may be related to compromised intestinal function and the high incidence of colon cancer in the aged population.

Aging↗

PubMed2002

Expression and localization of AQP5 in the stomach and duodenum of the rat.

The expression, localization, and regulation of aquaporin 5 (AQP5), a member of the water channel family of proteins, was investigated in tissues of the rat gastrointestinal tract. Reverse transcriptase--polymerase chain reaction (RT--PCR) detected AQP5 mRNA in the lower stomach and duodenum. DNA sequencing confirmed that the cDNA fragment amplified had the complete sequence of the AQP5 cDNA fragment. Western blot analysis indicated the expression of a 27 kDa molecular mass AQP5 protein in the lower stomach and duodenum, which size was the same as that found for the protein in the submandibular gland and lungs. By immunohistochemistry using the IgG affinity-purified AQP5 antibody, the pyloric gland and Brunner's gland were primarily stained in the lower stomach and duodenum, respectively; a strong staining appeared in the apical and lateral membranes in both glands. These results indicate that AQP5 is present in the rat lower stomach and duodenum where it may be involved in a water transport mechanism. These results also support the idea that AQP5, and probably other aquaporins, are involved in water secretion in the stomach and duodenum although the volume of water transported via AQPs is unclear.

Animals↗

PubMed1997

Influence of age on 1,25(OH)2-vitamin D3 activation of protein kinase C in rat duodenum.

We have studied age-related changes in the non-genomic regulation of protein kinase C (PKC) by 1,25-dihydroxy-vitamin D3 [1,25(OH)2D3] and their role in 1,25(OH)2D3-dependent calcium uptake in the rat duodenum. Treatment of duodenal mucosae from 3 month-old (young) rats with hormone physiological concentrations (0.1 nM) induced an acute and transient stimulation of total tissue PKC activity which was maximal at 1 min (+80%). The responses were evidenced up to 10 nM 1,25(OH)2D3. The duodenum from 22 to 24 month old (aged) rats exhibited higher basal PKC activity which was not significantly modified after addition of the hormone. In the young duodenum PKC activation by 1,25(OH)2D3 was dependent on extracellular Ca2+ influx as it could be abolished to a great extent by EGTA and the Ca2+ channel blocker verapamil. In addition, the Ca2+ ionophore A23187 elicited a marked stimulation of duodenal mucosae PKC in young rats but was without effects in aged animals. 1,25(OH)2D3 increased the influx of 45Ca2+ in duodenal mucosae of young rats in a dose-(0.1-1 nM) and time-(1-10 min) dependent fashion. This response to the hormone was impaired in aged animals. Similarly as 1,25(OH)2D3, the PKC activator dioctanoylglycerol (DOG) rapidly (1-5 min) increased [45Ca2+] influx in duodena from young rats whereas the response to DOG was blunted in senescent animals. Furthermore, PKC inhibitors (bisindolylmaleimide, staurosporine and compound H7) abolished 1,25(OH)2D3 stimulation of Ca2+ uptake in the young duodenum. These results suggest that 1,25(OH)2D3 regulates PKC activity in the mammalian duodenum by a non-genomic mechanism which involves the rapid influx of extracellular Ca2+, and that activation of PKC, in turn, mediates hormone stimulation of intestinal Ca2+ uptake. The data also indicates that 1,25(OH)2D3 regulation of Ca2+ transport through the PKC messenger system is impaired with aging.

Age Factors↗

PubMed1999

MRI of normal and abnormal duodenum using Half-Fourier Single-Shot RARE and gadolinium-enhanced spoiled gradient echo sequences.

The objective of this research was two-fold: First, to describe the normal and abnormal MR appearances of the duodenum using combined Half-Fourier Acquisition Single Shot RARE (HASTE) and gadolinium-enhanced standard and fat suppressed spoiled gradient echo (SGE) sequences. The second objective was to assess the ability of these combined sequences to detect and characterize duodenal diseases. MR examinations were performed on fifty consecutive patients with no clinical history of duodenal diseases, who were 1) imaged with HASTE and gadolinium-enhanced standard and fat suppressed SGE sequences and 2) referred to MR examination for reasons other than duodenal diseases, and were reviewed retrospectively to determine the normal MR appearances of the duodenum. A second population of patients with abnormal duodenum who were imaged with the same MR sequences were included in the second part of this study. This population was composed of 20 consecutive patients with subsequently proven duodenal abnormalities, including: malrotation (2), diverticula (4), intussusception (1), sprue (1), polyps (2), neurofibroma (1), lymphoma (1), Zollinger Ellison syndrome (1), metastatic disease (1), Crohn's disease (1), and wall thickening and duodenitis (5). Normal measurements of the duodenum are described. Abnormalities of wall thickness and duodenal masses required combined HASTE and gadolinium-enhanced SGE images to evaluate well. Abnormalities of the bowel lumen (e.g., diverticula and intussusception), and developmental variants (e.g., malrotation), were sufficiently visualized on HASTE images alone. Bowel inflammation was best shown on gadolinium-enhanced fat suppressed SGE images. HASTE and gadolinium-enhanced fat suppressed SGE sequences are complementary techniques for the demonstration of normal and abnormal duodenum. The combined use of both sequences allows evaluation of different aspects of bowel diseases; abnormalities of position, lumen, and contents are well shown on HASTE, while inflammation is best shown on gadolinium enhanced fat suppressed SGE, and wall thickening and masses are best evaluated with the combined use of both techniques.

Adolescent↗

PubMed2001

Strangulation of the duodenum by the uterus during late pregnancy in two cows.

Two Swiss Braunvieh cows in late pregnancy underwent surgery because of a rare form of ileus due to strangulation of the duodenum at its caudal flexure by the gravid uterus. The whole uterus had passed through a gap between the mesoduodenum and duodenum and with increasing weight had led to strangulation of the duodenum. This was possible since the mesoduodenum and both walls of the greater omentum adjacent to its caudal edge were not connected with the duodenum, probably due to a congenital inhibitory malformation. A transsection and an end-to-end anastomosis of the duodenum were necessary in both cases since it was impossible to retract the gravid uterus through the defect. Postoperative recovering was uneventful in both cows, which were discharged after seven and five days respectively and calved normally about two months later.

Anastomosis, Surgical↗

PubMed1998

Murine duodenum does not go through a "solid core" stage in its embryological development.

Embryological development of duodenum is believed to go through a "solid core" stage which subsequently vacuolizes. Failure of vacuolization is thought to be the cause of duodenal atresia. This study examines the embryological development of rat duodenum. Thirty-six time-mated Sprague-Dawley rats were studied. Six fetal duodenal specimens were obtained for each gestational day from day 9 to day 20. These specimens were fixed with formalin, sectioned, stained with haematoxylin and eosin and examined under microscope. The duodenal diameters and the lumen diameters at each gestational date were measured. The foregut started to form at the gestation stage of day 10. The lumen was narrowest on days 12 and 13, but the duodenum did not become a "solid core". No vacuolization was detected through out the development of the duodenum. Embryological development of rat duodenum did not go through a "solid core" stage.

Animals↗

PubMedDate not supplied

Operative approach in traumatic injuries of the duodenum.

BACKGROUND: The management of duodenal traumas remains controversial. The experience of Ankara Numune Training and Research Hospital Emergency Surgery Department with duodenal injuries during a 10-year period was analyzed to identify trends in operative management and sources of duodenum-related morbidity and mortality. METHODS AND RESULTS: Between 1994 and 2003, 1799 patients with blunt abdominal trauma were operated on and the incidence of duodenal trauma was 2.8% (50 patients). The injuries were penetrating in 31 (62%) patients and blunt in 19 (38%). Primary repair (PR) of injury was performed in 24 (48%) patients, primary repair and tube duodenostomy (PRTd) in 8 (16%) patients, complex repair (CR) in 11 (22%) patients, and exploration only without a duodenal procedure in 5 (10%) patients. Two of the patients died during laparotomy. The mortality rate was 12% and the incidence of duodenum-related morbidity was 12%. The overall morbidity rate was 40% (20 patients). The most commonly injured portion of the duodenum was DII (58%), and the most frequent cause of duodenum-related and overall morbidity in our series was Grade III duodenal injury. CONCLUSION: Our experience suggests that the use of primary repair in grade III injury may be associated with higher duodenum-related morbidity. Our recommendation is to use complex repair for grade III duodenal injuries.

Abdominal Injuries↗

PubMed1985

[Protein and amino acid metabolism in the digestive tract of growing young bulls. 2. Feed protein flow into the duodenum determined with 2,6-diaminopimelic acid as a marker for crude bacterial protein].

The experimental ascertainment of the pure feed protein flowing into the duodenum on the basis of the calculation of the difference between the NH3-free crude protein flowing into the duodenum and the bacterial crude protein determined by means of DAPA showed the following results after the testing of 28 different rations at a dry matter intake adequate to the production level: With a variation of the pure protein in the crude protein content of the ration between 40 and 90%, the quota of feed protein flowing into the duodenum is 52.5%, and with a variation of the pure protein in the crude protein content between 80 and 90% it is 40.6%. The quota of feed protein flowing into the duodenum shows a negative correlation to the apparent digestibility of the organic matter (y=231.7 -2.52x +/- 14.5). With a DM-intake adequate to the production level the quota of feed protein flowing into the duodenum is neither influenced by the flow rate (kg digesta/kg DM-intake) nor by the 'dilution rate' (g bacteria-free DMD/kg live weight 0.75/h).

Amino Acids↗

PubMed1986

Adaptation of the duodenum and ileum of the rat to mid-gut resection: enzyme activity and trace metal status.

Activities of the enzymes lactase, sucrase, maltase, alkaline phosphatase, and superoxide dismutase (SOD) were measured in mucosa of duodenum and ileum of the rat after 70% resection of mid-small intestine or sham operation (transection). We also measured the concentrations of zinc, copper, and manganese in several tissues to assess trace metal homeostasis postresection. Resection resulted in decreased specific activities of disaccharidases and alkaline phosphatase in duodenum, while specific activities remained unchanged in ileum. Specific activity of total SOD (the sum of Cu-Zn and Mn SOD) and Mn SOD was the same in duodenum after resection but was markedly increased in ileum. Tissue trace metal concentrations changed minimally. Because of postresection mucosal growth, total segmental activity of disaccharidases and alkaline phosphatase was the same in duodenum and increased in ileum of resected compared to transected rats. Segmental activity of total SOD and Mn SOD doubled in duodenum and trebled in ileum of resected as compared to transected rats. Thus, total segmental enzyme activity is maintained or increased postresection by increased enterocyte proliferation rate and mucosal growth.

Alkaline Phosphatase↗

PubMed1978

Retrograde movement of digesta in the duodenum of the chick: extent, frequency, and nutritional implications.

Movement of digesta from the duodenum to the gizzard of chicks was assessed by injection of 99mTc-diethyl-triamino-pentaacetic acid via an indwelling cannula in the hepatic bile duct. The change in location of isotope with time was followed with a Gamma Camera. About 40% of the injected isotope refluxed to the gizzard within 2 minutes of injection. Clearance of the isotope from the gizzard had a T1/2 of some 20 minutes. Some possible implications of retrograde movement of digesta were examined. Cholesterol, bile salts and pancreatic enzymes were found in the gizzard at 10% to 20% of duodenal concentrations. The proteolysis and lipolysis in the gizzard and duodenum were determined in chicks fed a duet containing 91Y as a non-absorbed reference substance. Thirty percent of the feed triglycerides were found hydrolysed in the gizzard as compared to 50% to 60% in the duodenum. Proteins were 30% to 50% trichloroacetic acid soluble in the gizzard reaching almost 70% in the duodenum. A small net secretion of both fatty acids and protein was observed in the gizzard, probably due to reflux of endogenous secretions from the duodenum. The nutritional significance of these results is discussed.

Animal Nutritional Physiological Phenomena↗

PubMed1975

Villous tumors of the duodenum.

Villous tumors of the duodenum are rare, but treatment may be problematic because of their association with invasive adenocarcinoma. Two cases of villous tumor of the duodenum are described and 39 other reported cases are reviewed. Presenting symptoms were bleeding 27%; obstruction 24%; jaundice 22% and vague dyspepsia 20%. Diagnosis may be made by radiographic barium contrast evaluation of the duodenum, especially with the addition of air contrast hypotonic studies and by fibro-optic endoscopy. Twenty-seven per cent of villous tumors of the duodenum are associated with adenocarcinoma. Invasive tumor is more common in patients over 50 years old (35%), in tumors of the third and fourth portions of the duodenum (44%) and in tumors over 4 cm in diameter (30%). Local excision is the treatment of choice for benign lesions. Pancreatico-duodenectomy is recommended for tumors which include invasive carcinoma in patients without distal metastases.

Adenocarcinoma↗

PubMed2004

Expression of Mg2+-dependent, HCO3- -stimulated adenine triphosphatase in the human duodenum.

BACKGROUND AND AIM: Mg2+-dependent, HCO3- -stimulated adenine triphosphatase (Mg2+-HCO3- -ATPase) is an enzyme that catabolizes ATP in the presence of HCO3- and Mg2+. The activity of this ATPase is known to be present in the duodenum, but its physiological role remains unclear. In the present study, the aim was to study the distribution and biochemical profiles of Mg2+-HCO3- -ATPase in the human duodenum. METHODS: The histochemistry of Mg2+-HCO3- -ATPase, its localization using electron microscopy (EMS), and the measurement of enzyme activity were carried out by using mucosal samples of the bulb, and the second and third portions of the duodenum, obtained from six volunteers by endoscopic biopsy. RESULTS: The Mg2+-HCO3- -ATPase was detected in the brush border along the luminal surface of human duodenal epithelial cells. The EMS confirmed its localization to the surface of microvilli. The activity of Mg2+-HCO3- -ATPase was higher in the distal portions of the human duodenum than in the bulb. Its maximal activity was obtained under a pH of 8.5, and in the presence of 1.0 mmol/L MgCl2 and 50 mmol/L NaHCO3, but the activity was undetectable in pH <7.4 or >9.5. CONCLUSION: The results of the present study suggested that Mg2+-HCO3- -ATPase may work for luminal alkalization in the distal portions of the human duodenum and may contribute to maintaining the activity of pancreatic digestive enzymes.

Ca(2+) Mg(2+)-ATPase↗