Ruminal transport and metabolism of short-chain fatty acids (SCFA) in vitro: effect of SCFA chain length and pH

Sehested, Jakob; Diernæs, L; Møller, Per; Skadhauge, Erik

doi:10.1016/s1095-6433(99)00074-4

Cited by 51 publications

(62 citation statements)

References 28 publications

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“…This finding is in agreement with a recent fluorescence study (45) and previous suggestions (12,24). Most likely, the thick stratum corneum of the ruminal epithelium (32) creates an unstirred layer with a pH distinct from the bulk of the ruminal solution; this might play a role in the diffusional uptake of H-SCFA (24,45,75,93).…”

Section: Effect Of Scfa On the Intraepithelial Ph Of The Intact Ruminsupporting

confidence: 91%

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Modulation of urea transport across sheep rumen epithelium in vitro by SCFA and CO₂

Abdoun

Stumpff

Rabbani

et al. 2010

American Journal of Physiology-Gastrointestinal and Liver Physi

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Urea transport across the gastrointestinal tract involves transporters of the urea transporter-B group, the regulation of which is poorly understood. The classical stimulatory effect of CO2 and the effect of short-chain fatty acids (SCFA) on the ruminal recycling of urea were investigated by using Ussing chamber and microelectrode techniques with isolated ruminal epithelium of sheep. The flux of urea was found to be phloretin sensitive and passive. At a luminal pH of 6.4, but not at 7.4, the addition of SCFA (40 mmol/l) or CO2/HCO 3 Ϫ (10% and 25 mmol/l) led to a fourfold increase in urea flux. The stepwise reduction of luminal pH in the presence of SCFA from 7.4 to 5.4 led to a bell-shaped modification of urea transport, with a maximum at pH 6.2. Lowering the pH in the absence of SCFA or CO2 had no effect. Inhibition of Na ϩ /H ϩ exchange increased urea flux at pH 7.4, with a decrease being seen at pH 6.4. In experiments with double-barreled, pH-sensitive microelectrodes, we confirmed the presence of an apical pH microclimate and demonstrated the acidifying effects of SCFA on the underlying epithelium. We confirm that the permeability of the ruminal epithelium to urea involves a phloretin-sensitive pathway. We present clear evidence for the regulation of urea transport by strategies that alter intracellular pH, with permeability being highest after a moderate decrease. The well-known postprandial stimulation of urea transport to the rumen in vivo may involve acute pH-dependent effects of intraruminal SCFA and CO2 on the function of existing urea transporters. pH i; urea transporter-B; short-chain fatty acids; microclimate; volatile fatty acid UREA, POSSIBLY BECAUSE OF its small size, was long thought to move passively across epithelia, depending only on the rate of delivery via blood. The urea permeability of cellular membranes has now been established to be several orders of magnitude above that of lipid membranes (11,92) and is coupled to the expression of specific urea-transporting proteins with channel-like kinetics (7,46,71,81,82,95). Whereas the role that these proteins play in the elegant renal concentrating mechanism has received much attention, their function and regulation in other parts of the body, such as the gut (39), continues to be poorly understood.In contrast to the paucity of our knowledge concerning extrarenal urea transport in humans, we have long known of the ability of camels, cows, or sheep to shift the excretion of urea from the kidney (62, 72) to the gastrointestinal tract (79). The transport of urea through the rumen epithelium was first demonstrated many years ago in vivo and in vitro (16,29,79,89) and the physiological significance is clear: in the rumen, dietary cellulose is broken down by bacteria that utilize ureanitrogen for the synthesis of microbial proteins. After passage into the duodenum, the amino acids of these proteins are absorbed and reach the liver, where new urea for secretion into the rumen can be formed. Recycling of nitrogen via urea secretion into the rumen thus ...

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Section: Effect Of Scfa On the Intraepithelial Ph Of The Intact Ruminsupporting

confidence: 91%

“…These data thus confirm the presence of an apical microclimate above the transporting layer of cells (24,45,75,93). Lowering the mucosal pH has slow acidifying effects on the cytosolic pH.…”

Section: Microelectrode Experimentssupporting

confidence: 76%

Modulation of urea transport across sheep rumen epithelium in vitro by SCFA and CO₂

Abdoun

Stumpff

Rabbani

et al. 2010

American Journal of Physiology-Gastrointestinal and Liver Physi

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“…Recent results obtained with the temporarily isolated washed rumen method in both sheep and steers (Kristensen and Harmon, 2006) support the hypothesis that absorbed at first pass, acetate, propionate and isobutyrate are almost fully recovered in the portal vein (portal recovery of 105% to 109%, 91% to 95%, 101% to 102%, respectively), whereas ruminal epithelium extensively metabolizes butyrate and valerate (portal recovery of 18% to 52%, 16% to 54%, respectively). These results also support a low production of acetate by the rumen epithelium, as noted in vitro (Sehested et al, 1999). At second pass, the PDV take up a large amount (20% to 40%) of the arterial acetate supply.…”

Section: Metabolism Of Vfa and Glucose By Portal-drained Viscerasupporting

confidence: 84%

Carbohydrate quantitative digestion and absorption in ruminants: from feed starch and fibre to nutrients available for tissues

Nozière

Ortigues-Marty

Loncke

et al. 2010

Animal

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Carbohydrates are the main source of energy in ruminants. Their site, extent and kinetics of digestion highly impact the amount and profile of nutrients delivered to peripheral tissues, and the responses of the animal, i.e. ingestion, efficiency of production, N and methane excretion, quality of products and welfare. Development of multi-objective feed evaluation systems thus requires a more integrated quantitative knowledge on carbohydrate digestion and yield of terminal products, as well as on their metabolism by splanchnic tissues. The objective of this paper is to review (i) quantitative knowledge on fibre, starch and sugar digestion, volatile fatty acids (VFA) and glucose production and splanchnic metabolism and (ii) modelling approaches which aim at representing and/or predicting nutrient fluxes in the digestive tract, portal and hepatic drainage. It shows that the representation of carbohydrate digestion and VFA yield is relatively homogeneous among models. Although published quantitative comparisons of these models are scarce, they stress that prediction of fibre digestion and VFA yield and composition is still not good enough for use in feed formulation, whereas prediction of microbial N yield and ruminal starch digestion seems to be more satisfactory. Uncertainties on VFA stoichiometric coefficients and absorption rates may partly explain the poor predictions of VFA. Hardly any mechanistic models have been developed on portal-drained viscera (PDV) metabolism whereas a few exist for liver metabolism. A qualitative comparison of these models is presented. Most are focused on dairy cows and their level of aggregation in the representation of nutrient fluxes and metabolism highly differs depending on their objectives. Quantitative comparison of these models is still lacking. However, recent advances have been achieved with the empirical prediction of VFA and glucose production and fluxes through PDV and liver based on the current INRA feed evaluation system. These advances are presented. They illustrate that empirical prediction of ruminal VFA and intestinal glucose production can be evaluated by comparison with measured net portal net fluxes. We also illustrate the potential synergy between empirical and mechanistic modelling. It is concluded that concomitant empirical and mechanistic approach may likely help to progress towards development of multi-objective feed evaluation systems based on nutrient fluxes.

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“…In this way, butyrate can partly substitute for extracellular Cl Ϫ in the CO 2 /HCO 3 Ϫ -buffered solution. Because a great proportion (ϳ95% under in vitro conditions) of absorbed butyrate is metabolized to CO 2 in REC (38), the positive effect of SCFA also results from its delivering substrate to the carbonic anhydrase reaction. Oxidative metabolism of SCFA is an important energy source for the epithelial cells themselves (4), and the reversible disassembly of V-ATPase into its V 0 and V 1 subunits acts as a type of regulation of its activity in response to a drop in energy supply (25).…”

Section: Methodsmentioning

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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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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Ruminal transport and metabolism of short-chain fatty acids (SCFA) in vitro: effect of SCFA chain length and pH

Cited by 51 publications

References 28 publications

Modulation of urea transport across sheep rumen epithelium in vitro by SCFA and CO₂

Modulation of urea transport across sheep rumen epithelium in vitro by SCFA and CO₂

Carbohydrate quantitative digestion and absorption in ruminants: from feed starch and fibre to nutrients available for tissues

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

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Ruminal transport and metabolism of short-chain fatty acids (SCFA) in vitro: effect of SCFA chain length and pH

Cited by 51 publications

References 28 publications

Modulation of urea transport across sheep rumen epithelium in vitro by SCFA and CO2

Modulation of urea transport across sheep rumen epithelium in vitro by SCFA and CO2

Carbohydrate quantitative digestion and absorption in ruminants: from feed starch and fibre to nutrients available for tissues

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

Contact Info

Product

Resources

About

Modulation of urea transport across sheep rumen epithelium in vitro by SCFA and CO₂

Modulation of urea transport across sheep rumen epithelium in vitro by SCFA and CO₂

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