Regulatory role of cAMP in transport of Na+, Cl- and short-chain fatty acids across sheep ruminal epithelium

Gäbel, Gotthold; Butter, Heidrun; Martens, Holger

doi:10.1017/s0958067099017583

Cited by 7 publications

(16 citation statements)

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“…An initial decrease in I sc could be seen in the presence and absence of mucosal cations and has already been reported in previous studies (5,7,38). It can be explained with an inhibitory impact of cAMP on the electroneutral Na ϩ /H ϩ exchanger in the apical membrane and a reduced electrogenic extrusion via Na ϩ -K ϩ -ATPase (5). A secondary increase in I sc could only be seen in the mucosal absence of Ca 2ϩ , i.e., when the relative contribution of the divalent cation-sensitive pathway to total sodium transport was enhanced (Fig.…”

Section: Regulation Of Ruminal Mg 2ϩ /Na ϩ Exchange and Transepithelisupporting

confidence: 86%

“…Previous studies (5,38) have shown that elevation of cAMP suppresses sodium transport through ruminal epithelium, possibly by inhibition of electroneutral sodium transport via the apical sodium proton exchanger. On the other hand, cAMP has been shown to stimulate Na ϩ /Mg 2ϩ exchange in various tissues, including the ruminal epithelium (3,10,23,25), decreasing the level of cytosolic magnesium.…”

Section: Effect Of Mucosal Replacement Of Ca 2ϩ and Mg 2ϩ On I Scmentioning

confidence: 94%

“…cAMP has been shown to decrease electroneutral Na ϩ absorption via Na ϩ /H ϩ exchange in rumen epithelium (5). This leads to an increase in pH at the epithelial surface (S. Leonhard-Marek and R. Busche, unpublished observation).…”

Section: Effect Of Mucosal Replacement Of Ca 2ϩ and Mg 2ϩ On I Scmentioning

confidence: 94%

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Basolateral Mg²⁺/Na⁺ exchange regulates apical nonselective cation channel in sheep rumen epithelium via cytosolic Mg²⁺

Leonhard-Marek¹,

Stumpff²,

Brinkmann³

et al. 2005

American Journal of Physiology-Gastrointestinal and Liver Physi

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High potassium diets lead to an inverse regulation of sodium and magnesium absorption in ruminants, suggesting some form of cross talk. Previous Ussing chamber experiments have demonstrated a divalent sensitive Na(+) conductance in the apical membrane of ruminal epithelium. Using patch-clamped ruminal epithelial cells, we could observe a divalent sensitive, nonselective cation conductance (NSCC) with K(+) permeability > Cs(+) permeability > Na(+) permeability. Conductance increased and rectification decreased when either Mg(2+) or both Ca(2+) and Mg(2+) were removed from the internal or external solution or both. The conductance could be blocked by Ba(2+), but not by tetraethylammonium (TEA). Subsequently, we studied this conductance measured as short-circuit current (I(sc)) in Ussing chambers. Forskolin, IBMX, and theophylline are known to block both I(sc) and Na transport across ruminal epithelium in the presence of divalent cations. When the NSCC was stimulated by removing mucosal calcium, an initial decrease in I(sc) was followed by a subsequent increase. The cAMP-mediated increase in I(sc) was reduced by low serosal Na(+) and serosal addition of imipramine or serosal amiloride and depended on the availability of mucosal magnesium. Luminal amiloride had no effect. Flux studies showed that low serosal Na(+) reduced (28)Mg fluxes from mucosal to serosal. The data suggest that cAMP stimulates basolateral Na(+)/Mg(2+) exchange, reducing cytosolic Mg. This increases sodium uptake through a magnesium-sensitive NSCC in the apical membrane. Likewise, the reduction in magnesium uptake that follows ingestion of high potassium fodder may facilitate sodium absorption, as observed in studies of ruminal osmoregulation. Possibly, grass tetany (hypomagnesemia) is a side effect of this useful mechanism.

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Section: Regulation Of Ruminal Mg 2ϩ /Na ϩ Exchange and Transepithelisupporting

confidence: 86%

Section: Effect Of Mucosal Replacement Of Ca 2ϩ and Mg 2ϩ On I Scmentioning

confidence: 94%

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Basolateral Mg²⁺/Na⁺ exchange regulates apical nonselective cation channel in sheep rumen epithelium via cytosolic Mg²⁺

Leonhard-Marek¹,

Stumpff²,

Brinkmann³

et al. 2005

American Journal of Physiology-Gastrointestinal and Liver Physi

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“…On the other hand, the shift from milk to solid feed has to be accompanied by qualitative and quantitative changes in absorptive and/or secretory functions of the developing rumen wall including transport mechanisms for electrolytes such as Na + and Cl -. Regarding this, it is well known that the rumen is an important site of active Na + absorption which is strongly interrelated with the permeation of Cl - (Martens et al, 1991;Gäbel et al, 1999), and in principle this could also be shown for 1 and 3 week-old lambs (Scharrer et al, 1981(Scharrer et al, , 1983.…”

Section: Introductionmentioning

confidence: 96%

Research Note: Postnatal Development of Electrolyte Transport in Calf Rumen as Affected by Weaning Time

Breves

Žitňan

Schröder

et al. 2002

Archiv für Tierernaehrung

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In a previous study we found a positive correlation between early weaning in calves and morphological parameters which were indicative of ruminal development, i.e. the length and width of the papillae. The objective of the present study was to determine to what extent this observation could be reflected by modulations of absorptive and secretory functions of the rumen mucosa. For this purpose the short-circuit currents (Isc) as a measure of electrogenic net ion fluxes and the transepithelial conductances (G(T)) as a measure of the overall tissue permeability were measured in vitro applying the Ussing-chamber technique. Simultaneously, the unidirectional flux rates of sodium and chloride across rumen wall epithelia were determined in the absence of electrochemical gradients. Under these conditions, significant positive net flux rates (Jnet) clearly indicate active mechanisms for electrolyte absorption. For the experiments 12 male Holstein calves 7 d of age were assigned to three groups of 4 animals each: milk group (I, slaughtered after 6 weeks of age), late weaning group (II, slaughtered after 9 weeks of age) and early weaning group (II, weaned after 6 weeks of age and slaughtered after 9 weeks of age). Whereas G(T) values remained unaffected by different age and feeding, Isc values were significantly affected by early weaning but were not influenced by age. Irrespective of weaning time active absorption of Na+ tended to be higher by about 60% in 9 weeks old animals. Active absorption of chloride was significantly increased in milk fed 9 weeke old calves and this effect was further stimulated by early weaning. In conclusion, the data show an increasing active Na+ absorption with age in calf rumen that could not be influenced by early weaning. Similarly, active Cl- absorption was initially increased during postnatal development and this effect could be stimulated further by early weaning.

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“…The importance of the undisturbed metabolism of SCFA for the health and performance of ruminants can hardly be overestimated, with their production in cattle reaching more than 100 mol/day and accounting for more than 75% of the total metabolizable energy in these animals [5,8,9]. Most of the SCFA are absorbed by the ruminal epithelium [10][11][12], and although a large fraction of butyrate is metabolized intracellularly [4,[13][14][15], both in vivo [14][15][16] and in vitro studies [17][18][19][20][21] have demonstrated that considerable amounts of acetate and propionate cross the basolateral membrane of the rumen in an unmetabolized state.…”

Section: Introductionmentioning

confidence: 99%

Cultured ruminal epithelial cells express a large-conductance channel permeable to chloride, bicarbonate, and acetate

Stumpff

Martens

Bilk

et al. 2008

Pflugers Arch - Eur J Physiol

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The absorption of short-chain fatty acids (SCFA) from the rumen requires efficient mechanisms for both apical uptake and basolateral extrusion. Previous studies suggest that the rumen expresses a basolateral chloride conductance that might be permeable to SCFA. In order to characterize this conductance in more detail, isolated cultured ruminal epithelial cells were studied with the patch-clamp technique, revealing a whole-cell conductance with p(Cl(-)) approximately p(NO(3) (-)) > p(HCO(3) (-)) > p(acetate(-)) > p(gluconate(-)). Currents could be blocked by diisothiocyanato-stilbene-2,2'-disulfonic acid (1 mmol l(-1) > 100 micromol l(-1)), 5-nitro-2-(3-phenylpropyl-amino)benzoic acid (50 micromol l(-1)), niflumic acid (100 micromol l(-1)), and p-chloromercuribenzoate (1 mmol l(-1)). Single-channel conductance was 350 +/- 7 pS for chloride and 142 +/- 7 pS for acetate. Open probability could be fitted with a three-state gating model. We propose a role for this channel in mediating the permeation of chloride, bicarbonate, and acetate across the basolateral membrane of the ruminal epithelium.

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Regulatory role of cAMP in transport of Na+, Cl- and short-chain fatty acids across sheep ruminal epithelium

Cited by 7 publications

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Basolateral Mg²⁺/Na⁺ exchange regulates apical nonselective cation channel in sheep rumen epithelium via cytosolic Mg²⁺

Basolateral Mg²⁺/Na⁺ exchange regulates apical nonselective cation channel in sheep rumen epithelium via cytosolic Mg²⁺

Research Note: Postnatal Development of Electrolyte Transport in Calf Rumen as Affected by Weaning Time

Cultured ruminal epithelial cells express a large-conductance channel permeable to chloride, bicarbonate, and acetate

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Regulatory role of cAMP in transport of Na+, Cl- and short-chain fatty acids across sheep ruminal epithelium

Cited by 7 publications

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Basolateral Mg2+/Na+ exchange regulates apical nonselective cation channel in sheep rumen epithelium via cytosolic Mg2+

Basolateral Mg2+/Na+ exchange regulates apical nonselective cation channel in sheep rumen epithelium via cytosolic Mg2+

Research Note: Postnatal Development of Electrolyte Transport in Calf Rumen as Affected by Weaning Time

Cultured ruminal epithelial cells express a large-conductance channel permeable to chloride, bicarbonate, and acetate

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Basolateral Mg²⁺/Na⁺ exchange regulates apical nonselective cation channel in sheep rumen epithelium via cytosolic Mg²⁺

Basolateral Mg²⁺/Na⁺ exchange regulates apical nonselective cation channel in sheep rumen epithelium via cytosolic Mg²⁺