Functional role of bicarbonate in propionate transport across guinea‐pig isolated caecum and proximal colon.

Engelhardt, W; Gros, Gerolf; Burmester, Marion; Hansen, Katrine Bagge; Becker, Geórgia Franco; Rechkemmer, Gerhard

doi:10.1113/jphysiol.1994.sp020198

Cited by 37 publications

(37 citation statements)

References 16 publications

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“…However, this finding tallies with the finding of von Engelhardt & Rechkemmer (1992) and von Engelhardt, Burmester, Hansen, Becker & Rechkemmer (1993), who showed that the fraction of short chain fatty acids taken up in the form of undissociated acid is considerably greater in the distal than in the proximal colon. Thus, if we follow the postulate of Mascolo, Rajendran & Binder (1991) and von Engelhardt, Gros, Burmester, Hansen, Becker & Rechkemmer (1994), that the remainder of short chain fatty acid uptake occurs via a transport mechanism exchanging bicarbonate for short chain fatty acid anions, we would indeed expect that the proximal colon needs a larger transport capacity for bicarbonate than the distal colon.…”

Section: Discussionmentioning

confidence: 99%

Mass spectrometric determination of HCO₃⁻ permeability and carbonic anhydrase activity in intact guinea‐pig colon epithelium

Böllert

Peters

Engelhardt³

et al. 1997

The Journal of Physiology

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A mass spectrometric method originally used in red blood cells was applied to suspensions of isolated colonocytes and intact colonic epithelium to measure the exchange of 18O between HCO3−, CO2 and H2O to determine intracellular carbonic anhydrase activity (Ai) and membrane bicarbonate permeability (P). In suspensions of isolated guinea‐pig colon epithelial cells, colonocytes, we found significantly higher values of Ai and P for cells derived from the proximal colon than for cells from the distal colon. In the case of Ai, this confirms earlier reports. When the 18O exchange process was observed across the mucosal (apical) side of intact colon mucosa, the estimated values of Ai were identical to those obtained for isolated colonocytes, for both the proximal and the distal part of the colon. This is considered to be strong evidence that this method can be applied to a layer of intact epithelium as well as to cell suspensions. The values of P obtained from the apical side of intact colon mucosa were 6 times higher than those estimated from measurements with isolated colonocytes. This indicates that the basolateral membrane of colon epithelium, which participates in the 18O exchange process in isolated colonocytes but not in the 18O exchange process across the apical side of intact mucosa, has a markedly lower bicarbonate permeability than the apical membrane. When the 18O exchange process was observed across the serosal (basolateral) side of intact colon mucosa, the P values, as expected, were low compared with the apical side of intact mucosa. However, rather unexpectedly, the Ai values derived from these measurements were 2–3 times lower than those obtained with isolated colonocytes. It appears possible that the latter finding is an artifact due to the submucosal tissue markedly slowing down CO2 diffusion from the bathing medium into the epithelial cells, thus causing an apparent fall in Ai. A i decreased and P increased with increasing temperature, as expected, when studied on the mucosal side of intact colon. This provides additional support for the validity of the method.

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Section: Discussionmentioning

confidence: 99%

Mass spectrometric determination of HCO₃⁻ permeability and carbonic anhydrase activity in intact guinea‐pig colon epithelium

Böllert

Peters

Engelhardt³

et al. 1997

The Journal of Physiology

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“…Maintenance and treatment of the animals was as described previously (Engelhardt et al, 1994). After decapitation, between 8.00-9.00·a.m., the abdomen was opened and the large intestine removed, cut into the different segments (caecum, proximal colon and distal colon) and rinsed with 25·mmol·l -1 Tris-SO 4 pH·8.7 to remove luminal contents.…”

Section: Animals Guinea Pigsmentioning

confidence: 99%

A distinct carbonic anhydrase in the mucus of the colon of humans and other mammals

Kleinke

Wagner

John³

et al. 2005

Journal of Experimental Biology

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SUMMARY We have collected gastrointestinal, mainly colonic, mucus from humans,guinea pigs, rats, and normal and carbonic anhydrase II (CAII)-deficient mice. In the mucus of all species, substantial CA activity was present. Using antibodies against human CA isoforms we found that the human mucus CA differs from cytosolic CAI and CAII, membrane-bound CAIV, and the secreted CAVI of saliva. The high sensitivity of mucus CA to acetazolamide rules out its identity with cytosolic CAIII. Partial sequences obtained from the purified human mucus CA show similarity, but not identity, with human CAI, and clear differences from the other known CAs. Additional evidence concerning the CA isoform present in mucus was obtained for the mucus CA of other species and was derived from: (1) the mucus of CAII-deficient mice, whose high CA activity confirms that it is not CAII that is responsible; (2) the inhibitory effect of iodide, which shows that mucus CA from mice, guinea pig and humans does not have the high anion sensitivity of CAI; (3) the inactivating effect of 0.2%SDS on guinea pig, mouse and human mucus CA, ruling out the SDS-resistant CAIV; and (4) the partitioning of guinea-pig mucus CA into the water phase in Triton X114 phase separation experiments, which also argues against its identity with membrane-bound CAs, such as CAIV. A comparison of colonic mucus CA activity in normal and germ-free rats indicates that the mucus CA is not of bacterial origin but is produced by the gastrointestinal tissues. We conclude(from its immunoreactivity, from iodide inhibition and from partial amino acid sequences) that mucus CA of human origin probably represents an isozyme, which is specific for mucus and is not identical with the known CA isozymes. The results obtained for mucus CA of other species collectively point in the same direction.

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“…It is obvious that a CA that is attached to the membrane itself is ideally suited for such a task. 25,26) Given the importance of CA in pH regulation in stomach tissues, the effect of increasing concentrations of omeprazole, famotidine, and ranitidine on bovine stomach outer peripheral CA, cytosolic CA, inner peripheral CA and integral CA was undertaken in this study. Outer peripheral, cytosolic, inner peripheral and integral stomach carbonic anhydrase isoenzymes from bovine stomach were separated 27) and then purified by Sepharose 4B-L-tyrosine-sulfanylamide affinity chromatography ( Table 1).…”

Section: Resultsmentioning

confidence: 99%

Effects of Omeprazole, Famotidine, and Ranitidine on the Enzyme Activities of Carbonic Anhydrase from Bovine Stomach in Vitro and Rat Erythrocytes in Vivo

Demir

Nadaroğlu

Demir

2004

Biological & Pharmaceutical Bulletin

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Carbonic anhydrase (carbonate hydrolyase, E.C. 4.2.1.1) isozymes are a family of zinc metalloenzymes that catalyze the interconversion of CO 2 and HCO 3 .Ϫ1,2) The enzyme is abundantly present in mammalian red blood cells and to a lesser extent in different types of tissues and secretory organs. 3,4) In addition, carbonic anhydrase have been obtained and characterized from plant, yeast and bacteria. [4][5][6][7][8][9][10] The important roles of the enzyme in various cell types have been extensively reviewed. 4,5,10) Human and most mammalian red blood cell carbonic anhydrases are known to comprise two isozymes, I and II, however, ruminants and cats have only one isozyme II. 4)Carbonic anhydrases facilitate the one-for-one electroneutral exchange of Cl Ϫ for HCO 3 Ϫ and thereby contribute to pH regulation, CO 2 metabolism, volume regulation, and maintenance of Cl Ϫ and HCO 3 Ϫ levels. 11) In our stomach lining the play a role in secreting acid, while the same enzymes help to make pancreatic juices alkaline and our saliva neutral. Thus, carbonic anhydrase isozymes perform different functions at their specific locations, and their absence or malfunction can lead to diseased states, ranging from the loss of acid production to stomach failure. 12,13) Therefore, we examined the effects of omeprazole, famotidine, and ranitidine on stomach CA and erythrocyte CA, and compared the results for the 3 drugs with each other.It has been reported that the activity levels of CA isoenzymes in human erythrocytes vary considerably under certain pathological and physiological conditions. Changes in CA activity have been associated with metabolic diseases such as diabetes mellitus and hypertension.14,15) It has been reported that the inhibition of CA was found to impair proton secretion into the proximal tubule lumen and thereby decreased bicarbonate reabsorption. At the same time, inhibition of CA was also found to decrease the rate of acidification of urine, producing alkaline urine and eventually metabolic acidosis. 16) Omeprazole is a specific inhibitor of the H ϩ , K ϩ -ATPase or 'proton pump' in parietal cells. This enzyme is responsible for the final step in the process of acid secretion; omeprazole blocks acid secretion in response to all stimuli. It has also been shown to be highly effective in healing ulcers which have failed to respond to H 2 -receptor antagonists, and has been extremely valuable in treating patients with Zollinger-Ellison syndrome.17) Famotidine and ranitidine are H 2 blockers. They are available in prescription strength and over the counter. These drugs provide short-term relief, but over doses H 2 blockers. 18)In the present study, the in vitro effects of omeprazole on CA isoenzymes purified from bovine stomach and the in vivo effects on the CA enzyme from rat erythrocytes were investigated. Furthermore, in vitro and in vivo studies were performed with famotidine and ranitidine, which are used as H 2 blockers. Using the I 50 values obtained (causing 50% inhibition of enzyme activity), clinically, undesir...

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Functional role of bicarbonate in propionate transport across guinea‐pig isolated caecum and proximal colon.

Cited by 37 publications

References 16 publications

Mass spectrometric determination of HCO₃⁻ permeability and carbonic anhydrase activity in intact guinea‐pig colon epithelium

Mass spectrometric determination of HCO₃⁻ permeability and carbonic anhydrase activity in intact guinea‐pig colon epithelium

A distinct carbonic anhydrase in the mucus of the colon of humans and other mammals

Effects of Omeprazole, Famotidine, and Ranitidine on the Enzyme Activities of Carbonic Anhydrase from Bovine Stomach in Vitro and Rat Erythrocytes in Vivo

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Functional role of bicarbonate in propionate transport across guinea‐pig isolated caecum and proximal colon.

Cited by 37 publications

References 16 publications

Mass spectrometric determination of HCO3− permeability and carbonic anhydrase activity in intact guinea‐pig colon epithelium

Mass spectrometric determination of HCO3− permeability and carbonic anhydrase activity in intact guinea‐pig colon epithelium

A distinct carbonic anhydrase in the mucus of the colon of humans and other mammals

Effects of Omeprazole, Famotidine, and Ranitidine on the Enzyme Activities of Carbonic Anhydrase from Bovine Stomach in Vitro and Rat Erythrocytes in Vivo

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Mass spectrometric determination of HCO₃⁻ permeability and carbonic anhydrase activity in intact guinea‐pig colon epithelium

Mass spectrometric determination of HCO₃⁻ permeability and carbonic anhydrase activity in intact guinea‐pig colon epithelium