Effects of short chain fatty acids and carbon dioxide on magnesium transport across sheep rumen epithelium

Leonhard-Marek, S.; Gäbel, Gotthold; Martens, H.

doi:10.1113/expphysiol.1998.sp004098

Cited by 39 publications

(34 citation statements)

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“…Part of the Mg 2ϩ influx is K ϩ sensitive and may represent electrodiffusive Mg 2ϩ uptake by an ion channel (35). The greater part (62%) is, however, K ϩ insensitive, and previous experiments carried out with isolated rumen epithelium and isolated ruminal epithelial cells (REC) in our laboratory have established that ruminal fermentation products [short-chain fatty acids (SCFA), CO 2 ] stimulate transepithelial Mg 2ϩ absorption (23) and Mg 2ϩ influx into REC (37). Initially, it was assumed that the stimulation of Mg 2ϩ transport was via Mg 2ϩ /H ϩ exchange in the apical membrane (23), by means of the proton load resulting from the absorption of SCFA in their protonized form and the intracellular hydration of CO 2 .…”

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confidence: 96%

“…The greater part (62%) is, however, K ϩ insensitive, and previous experiments carried out with isolated rumen epithelium and isolated ruminal epithelial cells (REC) in our laboratory have established that ruminal fermentation products [short-chain fatty acids (SCFA), CO 2 ] stimulate transepithelial Mg 2ϩ absorption (23) and Mg 2ϩ influx into REC (37). Initially, it was assumed that the stimulation of Mg 2ϩ transport was via Mg 2ϩ /H ϩ exchange in the apical membrane (23), by means of the proton load resulting from the absorption of SCFA in their protonized form and the intracellular hydration of CO 2 . More direct investigations with isolated REC have provided evidence for a symport of Mg 2ϩ with anions and confirmed that SCFA and CO 2 activate H ϩ efflux by the Na ϩ /H ϩ exchanger (37).…”

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Anion-dependent Mg²⁺influx and a role for a vacuolar H⁺-ATPase in sheep ruminal epithelial cells

Schweigel

Martens

2003

American Journal of Physiology-Gastrointestinal and Liver Physi

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The K+-insensitive component of Mg2+ influx in primary culture of ruminal epithelial cells (REC) was examined by means of fluorescence techniques. The effects of extracellular anions, ruminal fermentation products, and transport inhibitors on the intracellular free Mg2+ concentration ([Mg2+]i), Mg2+ uptake, and intracellular pH were determined. Under control conditions (HEPES-buffered high-NaCl medium), the [Mg2+]i of REC increased from 0.56 ± 0.14 to 0.76 ± 0.06 mM, corresponding to a Mg2+ uptake rate of 15 μM/min. Exposure to butyrate did not affect Mg2+ uptake, but it was stimulated (by 84 ± 19%) in the presence of [Formula: see text]. In contrast, Mg2+ uptake was strongly diminished if REC were suspended in [Formula: see text]-buffered high-KCl medium (22.3 ± 4 μM/min) rather than in HEPES-buffered KCl medium (37.5 ± 6 μM/min). After switching from high- to low-Cl– solution, [Mg2+]i was reduced from 0.64 ± 0.09 to 0.32 ± 0.16 mM and the [Formula: see text]-stimulated Mg2+ uptake was completely inhibited. Bumetanide and furosemide blocked the rate of Mg2+ uptake by 64 and 40%, respectively. Specific blockers of vacuolar H+-ATPase reduced the [Mg2+]i (36%) and Mg2+ influx (38%) into REC. We interpret this data to mean that the K+-insensitive Mg2+ influx into REC is mediated by a cotransport of Mg2+ and Cl– and is energized by an H+-ATPase. The stimulation of Mg2+ transport by ruminal fermentation products may result from a modulation of the H+-ATPase activity.

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confidence: 96%

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confidence: 99%

Anion-dependent Mg²⁺influx and a role for a vacuolar H⁺-ATPase in sheep ruminal epithelial cells

Schweigel

Martens

2003

American Journal of Physiology-Gastrointestinal and Liver Physi

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“…This variable interaction between K 1 intake and Mg 21 absorption has been quantified, permitting the prediction of Mg absorption (Weiss, 2004). The K 1 -insensitive Mg 21 absorption in the presence of high ruminal potassium is due to a second, electroneutral mechanism of Mg 21 absorption (Leonhard-Marek and Martens, 1996;Leonhard-Marek et al, 1998b Leonhard-Marek et al, 1998a, Leonhard-Marek, 1999Schweigel and Martens, 2003 (Schweigel and Martens, 2003;Etschmann et al, 2006).…”

Section: Absorption Of Magnesiummentioning

confidence: 99%

Transport of cations and anions across forestomach epithelia: conclusions from in vitro studies

Leonhard-Marek

Stumpff

Martens

2010

Animal

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Secretion of saliva as well as absorptive and secretory processes across forestomach epithelia ensures an optimal environment for microbial digestion in the forestomachs. Daily salivary secretion of sodium (Na 1 ) exceeds the amount found in plasma by a factor of 2 to 3, while the secretion of bicarbonate (HCO 3 2 ) is 6 to 8 times higher than the amount of HCO 3 2 in the total extracellular space. This implies a need for efficient absorptive mechanisms across forestomach epithelia to allow for an early recycling. While Na 1 is absorbed from all forestomachs via Na 1 /H 1 exchange and a non-selective cation channel that shows increased conductance at low concentrations of Mg 21 , Ca 21 or H 1 in the luminal microclima and at low intracellular Mg 21 , HCO 3 2 is secreted by the rumen for the buffering of ingesta but absorbed by the omasum to prevent liberation of CO 2 in the abomasum. Fermentation provides short chain fatty acids and ammonia (NH 3 ) that have to be absorbed both to meet nutrient requirements and maintain ruminal homeostasis of pH and osmolarity. The rumen is an important location for the absorption of essential minerals such as Mg 21 from the diet. Other ions can be absorbed, if delivered in sufficient amounts (Ca 21 , P i , K 1 , Cl 2 and NH 4 1 ). Although the presence of transport mechanisms for these electrolytes has been described earlier, our knowledge about their nature, regulation and crosstalk has increased greatly in the last years. New transport pathways have recently been added to our picture of epithelial transport across rumen and omasum, including an apical non-selective cation conductance, a basolateral anion conductance, an apical H 1 -ATPase, differently expressed anion exchangers and monocarboxylate transporters.Keywords: ruminants, sodium potassium magnesium and calcium, short chain fatty acids, chloride and bicarbonate, channels transporters and exchangers ImplicationsThe improved knowledge of ruminal ion transport clearly underlines its physiological meaning for the whole animal. For example, magnesium absorption is markedly reduced at low Mg and high K intake and the effect of potassium is diminished at high Mg intake. This variable interaction has been quantified recently permitting the prediction of Mg absorption. Great progress has also been made in understanding the interactions between the absorptive pathways for Na, short chain fatty acids and ammonium. The new findings on structure and regulation of various ion transporters will allow a better understanding of the challenges that different diets pose to the maintenance of homeostatic conditions within the rumen and within the cells of the surrounding epithelium, with the implications for the investigation of ruminal adaptation to different diets. Future studies on transport pathways should include the barrier function of rumen epithelium and its possible impairment under harsh feeding conditions.

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“…Three forms of Na ϩ -independent cation transport have been described: a Ca 2ϩ /Mg 2ϩ antiport in liver cells of the rat (Cefaratti et al 1998), where it appears to be restricted to the apical membrane of the cells; a Mg 2ϩ /choline exchange in rat erythrocytes (Ebel et al 2002); and a H ϩ -driven Mg 2ϩ extrusion in form of a 1 Mg 2ϩ /2 H ϩ antiport in epithelial cells from the colon and cecum of the rat (Scharrer and Lutz 1990) and possibly in the rumen of sheep (Leonhard-Marek et al 1998;see, however, Schweigel et al 2000).…”

Section: Introductionmentioning

confidence: 99%

Mg²⁺-Malate Co-Transport, a Mechanism for Na⁺-Independent Mg²⁺Transport in Neurons of the LeechHirudo medicinalis

Günzel

Hintz²,

Durry³

et al. 2005

Journal of Neurophysiology

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Effects of short chain fatty acids and carbon dioxide on magnesium transport across sheep rumen epithelium

Abstract: SUMMARYShort chain fatty acids (SCFAs)

Cited by 39 publications

References 23 publications

Anion-dependent Mg²⁺influx and a role for a vacuolar H⁺-ATPase in sheep ruminal epithelial cells

Anion-dependent Mg²⁺influx and a role for a vacuolar H⁺-ATPase in sheep ruminal epithelial cells

Transport of cations and anions across forestomach epithelia: conclusions from in vitro studies

Mg²⁺-Malate Co-Transport, a Mechanism for Na⁺-Independent Mg²⁺Transport in Neurons of the LeechHirudo medicinalis

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Effects of short chain fatty acids and carbon dioxide on magnesium transport across sheep rumen epithelium

Abstract: SUMMARYShort chain fatty acids (SCFAs)

Cited by 39 publications

References 23 publications

Anion-dependent Mg2+influx and a role for a vacuolar H+-ATPase in sheep ruminal epithelial cells

Anion-dependent Mg2+influx and a role for a vacuolar H+-ATPase in sheep ruminal epithelial cells

Transport of cations and anions across forestomach epithelia: conclusions from in vitro studies

Mg2+-Malate Co-Transport, a Mechanism for Na+-Independent Mg2+Transport in Neurons of the LeechHirudo medicinalis

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Anion-dependent Mg²⁺influx and a role for a vacuolar H⁺-ATPase in sheep ruminal epithelial cells

Anion-dependent Mg²⁺influx and a role for a vacuolar H⁺-ATPase in sheep ruminal epithelial cells

Mg²⁺-Malate Co-Transport, a Mechanism for Na⁺-Independent Mg²⁺Transport in Neurons of the LeechHirudo medicinalis