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  • Deoxycholate  (3)
  • Calcium transport  (2)
  • Electrolyte transport  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Forskolin induced chloride secretion across the isolated mucosa of rat colon descendens (1983)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 323 (1983), S. 355-360 
    Details
    ISSN: 1432-1912
    Keywords: Forskolin ; Chloride secretion ; Rat colon ; Electrolyte transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effects of forskolin, a diterpene reported to stimulate adenylate cyclase, on electrolyte transport across the isolated colonic mucosa of rat colon descendens were investigated. Forskolin, over a concentration range of 10−7–10−5 M, dose-dependently increased short circuit current (Isc) and transmural potential differences (Vms). The nearly 2-fold increase in Isc and Vms caused by forskolin was accompanied by a small increase in transmural conductance (Gt). The effects of forskolin were rapid and completely reversible without any loss in tissue sensitivity. Forskolin (5x10−6 M) inhibited the absorption of Na+ and reversed Cl− absorption to secretion. These effects were due to an inhibition of the mucosal-to-serosal fluxes of Na+ and Cl−. Ion substitution experiments revealed that the effects of forskolin were both Na+ and Cl− dependent and these ions were required in the serosal solution. Furosemide (10−4 M) as well as scilliroside (10−4 M) reversed and prevented the increase in Isc caused by forskolin. Adenylate cyclase activity in homogenates of colonic mucosa was increased 3-fold by forskolin. These results with rat colon are compared with those reported for rabbit colon and ileum and the mechanism of cyclic-AMP induced Cl− secretion in these epithelia is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00512476
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  • 2
    Electronic Resource
    Electronic Resource
    Pathway of sodium moving from blood to intestinal lumen under the influence of oxyphenisatin and deoxycholate (1976)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 293 (1976), S. 31-37 
    Details
    ISSN: 1432-1912
    Keywords: Colonic mucosa ; Oxyphenisatin ; Deoxycholate ; Sodium ; Intercellular pathway
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary 1. The transfer of 51CrEDTA and inulinsubstances which are distributed only in the extracellular space-across the rat colonic mucosa in vivo is increased by oxyphenisatin O (3.5 · 10−5 M) and deoxycholate D (3 · 10−3 M). 2. O and D do not change the size of the intra- and extracellular fluid compartments of the mucosa as measured with 51CrEDTA from the blood side. The sodium and potassium content of the mucosal tissue is not altered. Therefore the calculated intracellular concentrations of sodium and potassium remain constant. 3. The time course of the 22Na uptake into the mucosal epithelium is not influenced by O and D up to 5 min after i.v. injection. The specific activity of sodium, however, in the luminal fluid increases under the influence of O (twofold) and D (fivefold). The uptake of 22Na into the mucosal tissue after administration of 22Na into the intestinal lumen is not changed in presence of O and D. 4. We conclude that the net transport of sodium and water from blood to lumen under the influence of O and D occurs mainly via the intercellular way.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00498868
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  • 3
    Electronic Resource
    Electronic Resource
    Transfer of sodium and water through isolated rat colonic mucosa under the influence of deoxycholate and oxyphenisatin (1977)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 297 (1977), S. 185-190 
    Details
    ISSN: 1432-1912
    Keywords: Isolated rat colon ; Sodium transfer ; Water transfer ; Oxyphenisatin ; Deoxycholate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary 1. The influence of oxyphenisatin (OP), a diphenolic laxative, and deoxycholate (DC) on the transfer of sodium and water in an everted sac preparation of stripped rat colon was investigated. 2. OP (10−5 M, mucosal side) and DC (3×10−4 M, mucosal side) completely blocked net water and sodium absorption. Net movements from the serosal to the mucosal side could not be induced by higher concentrations of the drugs. 3. Unidirectional sodium movements in both directions were increased by OP and DC. 4. The effect of DC on the sodium flux from the serosal to the mucosal side was reversible. 5. The potassium content of the mucosal epithelium was not changed by DC and OP. 6. The integrity of the epithelium, as judged by light microscopy, was not disturbed by either drug under the experimental conditions. 7. It is concluded that DC and OP do not interfere with active transport mechanisms but increase the permeability of the epithelium to sodium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00499929
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  • 4
    Electronic Resource
    Electronic Resource
    Comparative study of the effect of cholera toxin and sodium deoxycholate on the paracellular permeability and on net fluid and electrolyte transfer in the rat colon (1980)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 312 (1980), S. 91-97 
    Details
    ISSN: 1432-1912
    Keywords: Rat colon mucosa ; Cholera toxin ; Deoxycholate ; Permeability ; Morphology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary 1. The effect of deoxycholate and cholera toxin on the transfer of water, sodium, potassium and chloride and on mucosal permeability was studied in perfusion experiments on rat colon in vivo. The influence of both secretagogues on surface morphology was assessed by scanning electron microscopy. 2. Deoxycholate turned the absorption of water, sodium and chloride to secretion and enhanced potassium secretion. Cholera toxin induced water and sodium secretion, inhibited chloride absorption and enhanced potassium secretion. 3. Deoxycholate increased reversibly the mucosal permeability as measured by the colonic clearance of 51CrEDTA and glucose, whereas cholera toxin decreased the colonic 51CrEDTA clearance. 4. Deoxycholate caused protrusion of the luminal cell surface and an increase of exfoliation of epithelial cells. The epithelial continuity was preserved. The only change induced by cholera toxin was an enhanced mucus extrusion. 5. Our results are consistent with the view that deoxycholate causes fluid secretion by filtration whereas cholera toxin enhances the secretory activity of the epithelium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00502580
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  • 5
    Electronic Resource
    Electronic Resource
    The role of the paracellular pathway in the net transport of calcium across the colonic muscosa (1986)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 334 (1986), S. 525-530 
    Details
    ISSN: 1432-1912
    Keywords: Colon ; Calcium transport ; Dexamethasone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Concentration dependent calcium fluxes across the colon descendens of the rat were measured in a modified Ussing chamber. Mucosa (m) to serosa (s) calcium flux showed a saturable component, whereas s to m calcium flux was linearly related to the calcium concentration. At low calcium concentrations net absorption and at concentration above 2.5 mmol/l net secretion of calcium was observed. The results obtained from the unidirectional calcium fluxes when clamping the transepithelial electrical potential agree well with those of the concentration dependence of the calcium fluxes: (1) Only m to s flux has a voltage independent component. (2) Calcium s to m movement is totally voltage dependent. (3) Diffusional s to m calcium flux is greater than the diffusional fraction of the m to s calcium flow. Dexamethasone, known to stimulate water absorption in the colon descendens by an activation of sodium transport, had no effect on the cellular mediated m to s calcium transport but significantly increased paracellular s to m flux parallel to that of the extracellular marker mannitol. This increase in paracellular s to m calcium and mannitol flux was completely abolished by amiloride, which is known to suppress the dexamethasone-induced stimulation in sodium and water absorption. The results demonstrate that the increased paracellular s to m calcium and mannitol flow is oppositely directed to the dexamethasone-induced net fluid movement as it could be expected on the basis of Ussing's “anomalous solvent drag” effect.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00569396
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  • 6
    Electronic Resource
    Electronic Resource
    Cellular and paracellular calcium transport in the rat ileum and the influence of 1α,25-dihydroxyvitamin D3 and dexamethasone (1987)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 336 (1987), S. 117-124 
    Details
    ISSN: 1432-1912
    Keywords: Ileal mucosa ; Calcium transport ; 1α,25-Dihydroxyvitamin D3 ; Dexamethasone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Concentration dependence of unidirectional calcium fluxes across the rat ileum freed from the serosa and the muscularis externa were measured in a modified Ussingchamber. Mucosa (m) to serosa (s) calcium flux showed a saturable component, whereas s to m calcium flux was linearly related to the calcium concentration between 0.125 mmol/1 and 5 mmol/1. At all calcium concentrations used net secretion of calcium was observed. The s to m flux of the simultaneously measured paracellular marker mannitol at all calcium concentrations was remarkably higher than the m to s flux, resulting in net mannitol secretion. The results obtained from the calcium fluxes when clamping the transepithelial electrical potential agree well with those of the concentration dependence of the calcium fluxes: 1. Only m to s flux has a voltage independent, transcellular component. 2. Calcium s to m flux is totally voltage dependent, i.e. diffusive. 3. Diffusional s to m calcium flux is about 80% greater than the diffusional fraction of the m to s flux. Omitting glucose from the bathing solution effected a decrease of the transepithelial electrical potential and of the short circuit current by 91% and 85% respectively; net calcium secretion was almost abolished and net mannitol secretion remarkably reduced. Addition of glucose, which stimulates water absorption in the ileum as a metabolic substrate, activated m to s but significantly more pronounced s to m calcium flux parallel to that of mannitol. Dexamethasone, known to stimulate sodium and water absorption in the ileum by activation of the Na,K-ATPase, effected an increase of the transepithelial electrical potential difference and of the short circuit current by about 100% but had no influence on tissue resistance; m to s and more pronounced s to m calcium flux was stimulated after the induction by dexamethasone and net calcium secretion was increased by 70%. After pretreatment with 1α,25-dihydroxyvitamin D3 tissue resistance was decreased by about 42%. The vitamin had no effect on net calcium or mannitol secretion but significantly increased bidirectional calcium and mannitol fluxes. Flux measurements in clamped preparations revealed: 1. 1α,25-dihydroxyvitamin D3 and dexamethasone has no effect on the cellular-mediated m to s calcium transport; 2. diffusive calcium flux in m to s and in the opposite direction, from s to m, is increased by the vitamin and by the hormone. In conclusion the net ileal calcium and mannitol secretion is the consequence of an asymmetry of the paracellular flux with a prevalence of the s to m flux over that in m to s direction. It is hypothesized that this prevalence is caused by an anomalous solvent drag effect. Paracellular calcium flux in both directions is increased by 1α,25-dihydroxyvitamin D3 and dexamethasone by different mechanisms, as indicated by the changes in the electrical parameters of the tissue.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00177761
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  • 7
    Electronic Resource
    Electronic Resource
    Storage of glycogen in rat colonic epithelium during induction of secretion and absorption in vitro (1990)
    Springer
    Cell & tissue research 261 (1990), S. 195-203 
    Details
    ISSN: 1432-0878
    Keywords: Intestine (large) ; Glycogen ; Electrolyte transport ; Electric field stimulation ; Forskolin ; Tetrodotoxin ; Rat (Wistar)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Changes induced in the ultrastructure of the epithelium of the rat colon descendens by long-term electric field stimulation (EFS) in an Ussing chamber were investigated. The anion secretion, which was induced by EFS and was measured by the short-circuit current, fell continuously during a 5 h stimulation. At the end of the stimulation period, small particles were observed in the epithelium; these did not appear in unstimulated control tissue. They were localized predominantly in the apical part of the cell. By staining with periodic acidthiosemicarbazide-silver proteinate and because of their sensitivity to α-amylase, they were identified as glycogen deposits. This storage of glycogen was time-dependent and was first visible after an EFS of 2 h. It did not appear if glucose was substituted in the bathing solution by sodium butyrate. Glycogen particles were also observed after addition of forskolin, which in contrast to EFS causes a high secretory activity that is stable over several hours. The surface cells contained significantly more glycogen than the crypt cells when secretion was stimulated by EFS or forskolin. The formation of glycogen during EFS was not prevented by tetrodotoxin (TTX). In contrast, TTX itself, which causes maximal absorptive activity by blocking secretomotor neurons, induced the appearance of glycogen in the enterocytes without EFS. However, in the presence of TTX, the amount of glycogen was the same in surface and crypt cells. The results demonstrate that the capacity to synthesize and store glycogen, which has up to now only been observed in embryonic or tumor epithelial cells, is still present in adult colonic mucosa. Procedures carried out to change the functional state of the epithelium seem to induce, at least in vitro, a disinhibition of this capacity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00329452
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