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Foerster RH, Lamprecht G, Rischmüller K, Berlin P, Rousing AQ, Sørensen MV, Leipziger J, Berg P. Urinary acid-base excretion deciphers high acid load from colonic bicarbonate loss in intestinal failure patients with ileocolonic anastomosis - Guidance for composition of parenteral support. Clin Nutr 2024; 43:1043-1050. [PMID: 38554476 DOI: 10.1016/j.clnu.2024.03.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2023] [Revised: 03/03/2024] [Accepted: 03/12/2024] [Indexed: 04/01/2024]
Abstract
BACKGROUND & AIMS Acid-base disturbances are common in short bowel (SB) patients due to increased intestinal bicarbonate loss. However, the resulting systemic acid load has not been quantified. Base excess is used to monitor metabolic acid-base disturbances but inadequately reflects the acid load. Our aim was to investigate the systemic acid/base load in SB-patients to obtain quantitative estimates to guide the composition of parenteral support. METHODS We calculated total acid load in SB patients by summing 24-h urinary net acid excretion (NAE) and the provision of base equivalents in parenteral support. We then compared differences among anatomical SB-types: jejunostomy (SB-J), jejunocolostomy (SB-JC), and jejunoileostomy (SB-JIC). 47 urine samples from 34 SB patients were analyzed for bicarbonate (HCO3-), ammonium (NH4+), and titratable acid (TA) concentrations. NAE was calculated as (TA + NH4+) - HCO3-. Mixed-effects repeated-measures models were used to statistically examine differences between SB-types and associations with parenteral nutrition and NAE. A healthy cohort served as control. RESULTS In comparison to SB-J, SB-JC patients had a 4.1 mmoL/l lower base excess (95% CI: -6.3 to -1.8) and an 84.5 mmol/day higher total acid load (CI: 41.3 to 127.7). There were no significant differences between SB-JIC and SB-J regarding base excess, NAE, or total acid load. Higher amounts of infused acetate, sodium, and chloride, but not the acetate/chloride ratio, were associated with lower NAE and higher base excess. CONCLUSIONS Due to increased colonic bicarbonate loss, patients with SB-JC have a ∼4.4-fold higher acid load than healthy controls. The ion transport mechanisms mediating this bicarbonate loss from the remaining colon need further experimental investigation. NAE could be a useful tool to adjust base infusion in SB.
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Affiliation(s)
- Robert H Foerster
- Rostock University Medical Center, Department of Medicine II, Division of Gastroenterology and Endocrinology, Rostock, Germany
| | - Georg Lamprecht
- Rostock University Medical Center, Department of Medicine II, Division of Gastroenterology and Endocrinology, Rostock, Germany.
| | - Karen Rischmüller
- Rostock University Medical Center, Department of Medicine II, Division of Gastroenterology and Endocrinology, Rostock, Germany
| | - Peggy Berlin
- Rostock University Medical Center, Department of Medicine II, Division of Gastroenterology and Endocrinology, Rostock, Germany
| | - Amalie Q Rousing
- Department of Biomedicine, Health, Aarhus University, Aarhus, Denmark
| | - Mads V Sørensen
- Department of Biomedicine, Health, Aarhus University, Aarhus, Denmark
| | - Jens Leipziger
- Department of Biomedicine, Health, Aarhus University, Aarhus, Denmark
| | - Peder Berg
- Department of Biomedicine, Health, Aarhus University, Aarhus, Denmark
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Svendsen SL, Kornvig S, Berg P, Jensen IS, Araujo IBBA, Larsen CK, Leipziger J, Sørensen MV. Dietary K + acts as a genuine diuretic. Acta Physiol (Oxf) 2022; 234:e13762. [PMID: 34984847 DOI: 10.1111/apha.13762] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Revised: 11/29/2021] [Accepted: 01/01/2022] [Indexed: 12/11/2022]
Abstract
K+ balance in mammals relies on regulated renal K+ excretion matching unregulated fluctuating K+ intake. Upon a K+ rich meal, rapid and powerful K+ excretion is needed. Renal K+ secretion is stimulated by the increased tubular flow. We speculated that high K+ intake acutely increases urinary flow to stimulate K+ excretion. METHODS Mice were K+ challenged through diets or gavage. Post K+ loading urinary output, osmolarity, [K+ ]u , [Na+ ]u , plasma osmolarity, [copeptin]p , [K+ ]p , and [Na+ ]p were measured. To locate the mechanism of K+ -induced diuresis in the glomerular/tubular system we measured creatinine excretion and assessed functional transport in isolated perfused TALs and CDs during an acute [K+ ]bl switch from 3.6 to 6.5 mM. Molecular adaptations of transport proteins involved in water reabsorption were investigated by immunoblotting. RESULTS (1) Mice switched from a 1% to 2% K+ diet increased diuresis within 12 hours and reciprocally reduced diuresis when switched from 1% to 0.01% K+ diet. (2) A single K+ gavage load, corresponding to 25%-50% of daily K+ intake, induced 100% increase in diuresis within 30 minutes. This occurred despite augmented plasma osmolarity and AVP synthesis. (3) K+ gavage did not change GFR. (4) In isolated perfused TALs, shifting [K+ ]bl from 3.6 to 6.5 mM did not affect AVP-induced NaCl transport. (5) In sharp contrast, in isolated perfused CDs, shifting [K+ ]bl from 3.6 to 6.5 mM markedly reduced CD AVP sensitivity, ie inhibited water absorption. CONCLUSION Dietary K+ loading induces a rapidly on-setting diuresis. The mechanism of K+ -induced diuresis involves desensitization of the CD to AVP.
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Affiliation(s)
- Samuel L. Svendsen
- Department of Biomedicine, Physiology, Health Aarhus University Aarhus C Denmark
| | - Simon Kornvig
- Department of Biomedicine, Physiology, Health Aarhus University Aarhus C Denmark
| | - Peder Berg
- Department of Biomedicine, Physiology, Health Aarhus University Aarhus C Denmark
| | - Iben S. Jensen
- Department of Biomedicine, Physiology, Health Aarhus University Aarhus C Denmark
| | | | - Casper K. Larsen
- Department of Biomedicine, Physiology, Health Aarhus University Aarhus C Denmark
| | - Jens Leipziger
- Department of Biomedicine, Physiology, Health Aarhus University Aarhus C Denmark
| | - Mads V. Sørensen
- Department of Biomedicine, Physiology, Health Aarhus University Aarhus C Denmark
- Aarhus Institute for Advanced Studies (AIAS) Aarhus University Aarhus C Denmark
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Ayasse N, Berg P, Andersen JF, Svendsen SL, Sørensen MV, Fedosova NU, Lynch IJ, Wingo CS, Leipziger J. Benzamil-mediated urine alkalization is caused by the inhibition of H +-K +-ATPases. Am J Physiol Renal Physiol 2021; 320:F596-F607. [PMID: 33554781 DOI: 10.1152/ajprenal.00444.2020] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Epithelial Na+ channel (ENaC) blockers elicit acute and substantial increases of urinary pH. The underlying mechanism remains to be understood. Here, we evaluated if benzamil-induced urine alkalization is mediated by an acute reduction in H+ secretion via renal H+-K+-ATPases (HKAs). Experiments were performed in vivo on HKA double-knockout and wild-type mice. Alterations in dietary K+ intake were used to change renal HKA and ENaC activity. The acute effects of benzamil (0.2 µg/g body wt, sufficient to block ENaC) on urine flow rate and urinary electrolyte and acid excretion were monitored in anesthetized, bladder-catheterized animals. We observed that benzamil acutely increased urinary pH (ΔpH: 0.33 ± 0.07) and reduced NH4+ and titratable acid excretion and that these effects were distinctly enhanced in animals fed a low-K+ diet (ΔpH: 0.74 ± 0.12), a condition when ENaC activity is low. In contrast, benzamil did not affect urine acid excretion in animals kept on a high-K+ diet (i.e., during high ENaC activity). Thus, urine alkalization appeared completely uncoupled from ENaC function. The absence of benzamil-induced urinary alkalization in HKA double-knockout mice confirmed the direct involvement of these enzymes. The inhibitory effect of benzamil was also shown in vitro for the pig α1-isoform of HKA. These results suggest a revised explanation of the benzamil effect on renal acid-base excretion. Considering the conditions used here, we suggest that it is caused by a direct inhibition of HKAs in the collecting duct and not by inhibition of the ENaC function.NEW & NOTEWORTHY Bolus application of epithelial Na+ channel (EnaC) blockers causes marked and acute increases of urine pH. Here, we provide evidence that the underlying mechanism involves direct inhibition of the H+-K+ pump in the collecting duct. This could provide a fundamental revision of the previously assumed mechanism that suggested a key role of ENaC inhibition in this response.
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Affiliation(s)
- Niklas Ayasse
- Department of Biomedicine, Physiology, Aarhus University, Aarhus, Denmark
| | - Peder Berg
- Department of Biomedicine, Physiology, Aarhus University, Aarhus, Denmark
| | | | | | - Mads V Sørensen
- Department of Biomedicine, Physiology, Aarhus University, Aarhus, Denmark
| | - Natalya U Fedosova
- Department of Biomedicine, Physiology, Aarhus University, Aarhus, Denmark
| | - I Jeanette Lynch
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida, Gainesville, Florida.,North Florida/South Georgia Veterans Health System, Gainesville, Florida
| | - Charles S Wingo
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida, Gainesville, Florida.,North Florida/South Georgia Veterans Health System, Gainesville, Florida
| | - Jens Leipziger
- Department of Biomedicine, Physiology, Aarhus University, Aarhus, Denmark.,Aarhus Institute of Advanced Studies, Aarhus University, Aarhus, Denmark
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Jensen IS, Larsen CK, Leipziger J, Sørensen MV. Na(+) dependence of K(+) -induced natriuresis, kaliuresis and Na(+) /Cl(-) cotransporter dephosphorylation. Acta Physiol (Oxf) 2016; 218:49-61. [PMID: 27172453 DOI: 10.1111/apha.12707] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2015] [Revised: 01/26/2016] [Accepted: 05/09/2016] [Indexed: 12/01/2022]
Abstract
AIM High dietary K(+) intake is associated with protection against hypertension. In mammals, acute K(+) intake induces natriuresis and kaliuresis, associated with a marked dephosphorylation of the renal Na(+) /Cl(-) cotransporter (NCC). It has been suggested that reduced activity of NCC increases the driving force for more distal tubular epithelial Na(+) channel (ENaC)-dependent K(+) secretion. This study investigated the ENaC dependence of urinary K(+) and Na(+) excretion following acute K(+) loading. METHODS Mice were fed low (0.03%), control (0.2%) or high (2%) Na(+) diets for 25 days to preserve or promote Na(+) loss and thus ENaC activity. Once a week, the mice received either K(+) -containing gavage or a control gavage. Following the gavage treatment, the mice were placed in metabolic cages and urine was collected in real time. ENaC dependence of kaliuresis was assessed by benzamil injections prior to gavage. RESULTS We confirmed that dietary Na(+) content is inversely related to plasma aldosterone, NCC phosphorylation and ENaC cleavage products. The novel findings were as follows: (i) acute K(+) feeding caused NCC dephosphorylation in all dietary groups; (ii) under all dietary conditions, K(+) loading induced natriuresis; (iii) high Na(+) diet markedly reduced the K(+) excretion following K(+) gavage; (iv) benzamil injection prior to K(+) loading increased natriuresis, decreased kaliuresis and eliminated the differences between the dietary groups. CONCLUSION These data indicate that acute K(+) -induced kaliuresis is ENaC dependent. Maximal K(+) excretion rates are attenuated when ENaC is physiologically down-regulated or pharmacologically blocked. NCC is dephosphorylated following acute K(+) loading under all dietary Na(+) regimens. This leads to natriuresis, even in severely Na(+) -restricted animals.
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Affiliation(s)
- Iben S. Jensen
- Institute of Biomedicine, Physiology; Aarhus University; Denmark
| | - Casper K. Larsen
- Institute of Biomedicine, Physiology; Aarhus University; Denmark
| | - Jens Leipziger
- Institute of Biomedicine, Physiology; Aarhus University; Denmark
| | - Mads V. Sørensen
- Institute of Biomedicine, Physiology; Aarhus University; Denmark
- Aarhus Institute of Advanced Studies (AIAS); Aarhus University; Aarhus Denmark
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Sørensen MV, Sausbier M, Ruth P, Seidler U, Riederer B, Praetorius HA, Leipziger J. Adrenaline-induced colonic K+ secretion is mediated by KCa1.1 (BK) channels. J Physiol 2010; 588:1763-77. [PMID: 20351045 PMCID: PMC2887993 DOI: 10.1113/jphysiol.2009.181933] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2009] [Accepted: 03/29/2010] [Indexed: 11/08/2022] Open
Abstract
Colonic epithelial K(+) secretion is a two-step transport process with initial K(+) uptake over the basolateral membrane followed by K(+) channel-dependent exit into the lumen. In this process the large-conductance, Ca(2+)-activated K(Ca)1.1 (BK) channel has been identified as the only apparent secretory K(+) channel in the apical membrane of the murine distal colon. The BK channel is responsible for both resting and Ca(2+)-activated colonic K(+) secretion and is up-regulated by aldosterone. Agonists (e.g. adrenaline) that elevate cAMP are potent activators of distal colonic K(+) secretion. However, the secretory K(+) channel responsible for cAMP-induced K(+) secretion remains to be defined. In this study we used the Ussing chamber to identify adrenaline-induced electrogenic K(+) secretion. We found that the adrenaline-induced electrogenic ion secretion is a compound effect dominated by anion secretion and a smaller electrically opposing K(+) secretion. Using tissue from (i) BK wildtype (BK(+/+)) and knockout (BK(/)) and (ii) cystic fibrosis transmembrane regulator (CFTR) wildtype (CFTR(+/+)) and knockout (CFTR(/)) mice we were able to isolate the adrenaline-induced K(+) secretion. We found that adrenaline-induced K(+) secretion: (1) is absent in colonic epithelia from BK(/) mice, (2) is greatly up-regulated in mice on a high K(+) diet and (3) is present as sustained positive current in colonic epithelia from CFTR(/) mice. We identified two known C-terminal BK alpha-subunit splice variants in colonic enterocytes (STREX and ZERO). Importantly, the ZERO variant known to be activated by cAMP is differentially up-regulated in enterocytes from animals on a high K(+) diet. In summary, these results strongly suggest that the adrenaline-induced distal colonic K(+) secretion is mediated by the BK channel and probably involves aldosterone-induced ZERO splice variant up-regulation.
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Affiliation(s)
- Mads V Sørensen
- Department of Physiology and Biophysics, The Water and Salt Research Center, Aarhus University, 8000 Aarhus C, Denmark
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Sørensen MV, Matos JE, Sausbier M, Sausbier U, Ruth P, Praetorius HA, Leipziger J. Aldosterone increases KCa1.1 (BK) channel-mediated colonic K+ secretion. J Physiol 2008; 586:4251-64. [PMID: 18617563 DOI: 10.1113/jphysiol.2008.156968] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Mammalian K(+) homeostasis results from highly regulated renal and intestinal absorption and secretion, which balances the unregulated K(+) intake. Aldosterone is known to enhance both renal and colonic K(+) secretion. In mouse distal colon K(+) secretion occurs exclusively via luminal K(Ca)1.1 (BK) channels. Here we investigate if aldosterone stimulates colonic K(+) secretion via BK channels. Luminal Ba(2+) and iberiotoxin (IBTX)-sensitive electrogenic K(+) secretion was measured in Ussing chambers. In vivo aldosterone was augmented via a high K(+) diet. High K(+) diet led to a 2-fold increase of luminal Ba(2+) and IBTX-sensitive short-circuit current in distal mouse colonic mucosa. This effect was absent in BK alpha-subunit-deficient (BK(-/-)) mice. The resting and diet-induced K(+) secretion was stimulated by luminal ionomycin. In BK(-/-) mice luminal ionomycin did not stimulate K(+) secretion. In vitro addition of aldosterone likewise triggered a 2-fold increase in K(+) secretion, which was inhibited by the mineralocorticoid receptor antagonist spironolactone and the BK channel blocker IBTX. Semi-quantification of mRNA from colonic crypts showed up-regulation of BK alpha- and beta(2)-subunits in high K(+) diet mice. The BK channel could be detected luminally in colonic crypt cells by immunohistochemistry. The expression level of the channel in the luminal membrane was strongly up-regulated in K(+)-loaded animals. Taken together, these data strongly suggest that aldosterone-induced K(+) secretion occurs via increased expression of luminal BK channels.
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Affiliation(s)
- Mads V Sørensen
- Institute of Physiology and Biophysics, The Water and Salt Research Center, University of Aarhus, 8000 Aarhus C, Denmark
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