Metabolic Acidosis In Rat Research Articles

Oral pyruvate prevents high-intensity interval exercise-induced metabolic acidosis in rats by promoting lactate dehydrogenase reaction.

There is no denying the clinical benefits of exogenous pyruvate in the treatment of pathological metabolic acidosis. However, whether it can prevent exercise physiological metabolic acidosis, delay the occurrence of exercise fatigue, and improve the beneficial effects of exercise and its internal mechanism remain unclear. We randomly divided 24 male SD rats into 3 groups: one group was a control without exercise (CC, n = 8), and the other two groups were supplemented with 616 mg/kg/day pyruvate (EP, n = 8) or distilled water of equal volume (EC, n = 8). These groups completed acute high-intensity interval exercise (HIIE) after 7 days of supplementation. The acid metabolism variables were measured immediately after exercise including blood pH (pHe), base excess (BE), HCO3 -, blood lactic acid and skeletal muscle pH (pHi). The redox state was determined by measuring the oxidized coenzyme I/reduced coenzyme I (nicotinamide adenine dinucleotide [NAD+]/reduced NAD+ [NADH]) ratio and lactate/pyruvate (L/P) ratio. In addition, the activities of lactate dehydrogenase A (LDHA), hexokinase (HK), phosphofructokinase (PFK) and pyruvate kinase (PK) were determined by ELISA. Pyruvate supplementation significantly reversed the decrease of pHe, BE, HCO3 - and pHi values after HIIE (p < 0.001), while significantly increased the activities of LDHA (p = 0.048), HK (p = 0.006), and PFK (p = 0.047). Compared with the CC, the NAD+/NADH (p = 0.008) ratio and the activities of LDHA (p = 0.002), HK (p < 0.001), PFK (p < 0.001), and PK (p = 0.006) were significantly improved in EP group. This study provides compelling evidence that oral pyruvate attenuates HIIE-induced intracellular and extracellular acidification, possibly due to increased activity of LDHA, which promotes the absorption of H+ in the LDH reaction. The beneficial effects of improving the redox state and glycolysis rate were also shown. Our results suggest that pyruvate can be used as an oral nutritional supplement to buffer HIIE induced metabolic acidosis.

Considerations about an experimental model of chronic metabolic acidosis in rats.

Considerations about an experimental model of chronic metabolic acidosis in rats.

Effects of honey supplementation on renal dysfunction and metabolic acidosis in rats with high-fat diet-induced chronic kidney disease.

Background Metabolic diseases are associated with impaired renal function which accelerates chronic kidney disease (CKD) progression. The aim of this study was to investigate the effects of 16-week honey supplementation on renal function, metabolic acidosis and renal abnormalities in Wistar rats fed a high-fat diet (HFD). Methods Wistar rats were fed a HFD and sucrose (30%) solution and randomly grouped and treated. Group 1 was fed rat chow and treated with drinking water while groups 2, 3, 4 and 5 were fed a HFD and treated with drinking water, 1, 2 and 3 g/kg body weight (BW) of honey, respectively, once daily for 16 weeks. After the rats were sacrificed, the serum samples were obtained and used for the analysis of total cholesterol, urea, creatinine, sodium, potassium, calcium, bicarbonates and chloride ions. Histopathological examinations of the kidneys were performed. Results The serum creatinine and anion gap levels were significantly (p < 0.01) higher while the levels of serum total calcium and ionized fraction were significantly (p < 0.01) lower in HFD-fed control rats than in chow-fed rats. The kidney of HFD-fed control rats was characterized by tubular necrosis, glomerular atrophy, hemorrhage and severe focal aggregate inflammatory (FAIC) cells. Honey treatment (1, 2 or 3 g/kg BW) prevented elevations in serum creatinine while it restored serum levels of total calcium and ionized calcium towards those in rats fed chow only. All the three doses of honey also significantly (p < 0.01) reduced anion gap and ameliorated renal lesions. Honey treatment (2 g/kg BW) significantly (p < 0.05) increased bicarbonate and chloride ion in HFD-fed rats compared with HFD-fed control rats. Conclusions Sixteen-week honey supplementation ameliorates renal dysfunction, metabolic acidosis and renal morphological abnormalities in HFD-fed Wistar rats.

Correction of acid base disorders in rats with acute ethylene glycol poisoning

The aim of the article. The aim of this study was to evaluation of the effectiveness of standard antidote therapy and dimephosphon administration in rats with acute ethylene glycol poisoning. The tasks of the study included modeling acute ethylene glycol poisoning in rats, conducting experimental therapy with ethanol antidote in combination with sodium bicarbonate and dimephosphon therapy, comparing the effectiveness of drugs in relation to indicators of acid-base state impairment and renal function.&#x0D; Materials and methods. Ethylene glycol (EG) was administered per os to Wistar male rats (190210 g b.w.) at a single dose of 6 mL/kg b.w. through an atraumatic gastric tube. The animals were divided into 4 groups of 6 individuals each: intact (negative control), EG poisoning (positive control), EG + standard antidote therapy, EG + dimephosphon therapy. Experimental therapy was carried out for first 24 hours using standard antidote therapy: ethanol (30% solution 2 mL/kg b.w. i.p. after 1, 4, 6, 12, 18 hours) and sodium bicarbonate (4 % solution 6 mL/kg b.w. i.p. 3 times on the first day), as well as administration of dimephosphon (150 mg/kg i.p. 3 times on the first day, 450 mg/kg b.w. per day). Daily urine on day 3 after poisoning was collected in metabolic cages. Creatinine concentration in urine and blood serum samples were measured, and creatinine clearance was calculated. After 24 hours of therapy, the pH, level of sodium, potassium, calcium, magnesium, chlorides, bicarbonates, lactate, D-3-hydroxybutyrate, albumin, urea and creatinine (measured parameters) were determined in venous blood samples. Anion gap, ∆рН, ∆AG, ∆HCO3, ∆AG/∆HCO3 and ∆Gap were calculated. The mechanism of death was determined for the dead animals. Data processing was performed using GraphPad Prism 6.0.&#x0D; Results. Acute poisoning of rats with ethylene glycol leads to the development of toxic encephalopathy and nephropathy, acid-base abnormalities, high anion gap metabolic acidosis due to the presence of metabolites, as well as lactate-ketoacidosis due to depression of the central nervous system. 100% of the EG-treated (12 mL/kg b.w.) animals died within 3 days. Metabolic acidosis in combination with hypermagnesemia had provided a cardiodepressive effect, which with direct nephrotoxic and neurotoxic effects contributed to the development of a mixed variant of thanatogenesis and death. Death comes from toxic encephalopathy and nephropathy, high anion gap metabolic acidosis caused by direct nephrotoxic and neurotoxic effects of EG and its metabolites. The standard antidote therapy with ethanol in combination with sodium bicarbonate prevented a pH shift, lactic acidosis and ketoacidosis, an increase in urea, but did not affect the level of bicarbonate (p = 0,048), creatinine and its clearance (p = 0,037) and the anion gap (p = 0,033). The dimephosphon therapy prevented a decrease in creatinine clearance and blood bicarbonate level, limited the increase in lactate dehydrogenase activity, had a more pronounced effect on the AG and ∆AG (p = 0,042), but did not affect the hypocalcemia (p = 0,0076) and hypoalbuminemia (p = 0,021).&#x0D; Conclusion. Acute ethylene glycol poisoning leads to the development of a mixed variant of thanatogenesis with damage to the central nervous and urinary systems, as well as the heart. Autopsy and histopathology confirmed the cause of animal death. In the model at a dose of 6 mL/kg of EG the dimephosphon therapy was more conducive to the correction of the main markers of high anion gap metabolic acidosis (HAGMA) than standard antidote therapy (both measured and calculated, p 0,05). The dimephosphon therapy prevented a decrease in creatinine clearance. A comparative analysis of two methods for the correction of high anion gap metabolic acidosis in rats in acute poisoning with ethylene glycol showed that dimephosphon therapy vs. standard antidote therapy had a stronger effect on markers of metabolic acidosis and renal impairment.

Roux-en-Y gastric bypass surgery reduces bone mineral density and induces metabolic acidosis in rats

Roux-en-Y gastric bypass (RYGB) surgery leads to bone loss in humans, which may be caused by vitamin D and calcium malabsorption and subsequent secondary hyperparathyroidism. However, because these conditions occur frequently in obese people, it is unclear whether they are the primary causes of bone loss after RYGB. To determine the contribution of calcium and vitamin D malabsorption to bone loss in a rat RYGB model, adult male Wistar rats were randomized for RYGB surgery, sham-operation-ad libitum fed, or sham-operation-body weight-matched. Bone mineral density, calcium and phosphorus balance, acid-base status, and markers of bone turnover were assessed at different time points for 14 wk after surgery. Bone mineral density decreased for several weeks after RYGB. Intestinal calcium absorption was reduced early after surgery, but plasma calcium and parathyroid hormone levels were normal. 25-hydroxyvitamin D levels decreased, while levels of active 1,25-dihydroxyvitamin D increased after surgery. RYGB rats displayed metabolic acidosis due to increased plasma lactate levels and increased urinary calcium loss throughout the study. These results suggest that initial calcium malabsorption may play a key role in bone loss early after RYGB in rats, but other factors, including chronic metabolic acidosis, contribute to insufficient bone restoration after normalization of intestinal calcium absorption. Secondary hyperparathyroidism is not involved in postoperative bone loss. Upregulated vitamin D activation may compensate for any vitamin D malabsorption.

The hyperpolarization-activated cyclic nucleotide-gated HCN2 channel transports ammonium in the distal nephron

Recent studies have identified Rhesus proteins as important molecules for ammonia transport in acid-secreting intercalated cells in the distal nephron. Here, we provide evidence for an additional molecule that can mediate NH3/NH4 excretion, the subtype 2 of the hyperpolarization-activated cyclic nucleotide-gated channel family (HCN2), in collecting ducts in rat renal cortex and medulla. Chronic metabolic acidosis in rats did not alter HCN2 protein expression but downregulated the relative abundance of HCN2 mRNA. Its cDNA was identical to the homolog from the brain and the protein was post-translationally modified by N-type glycosylation. Electrophysiological recordings in Xenopus oocytes injected with HCN2 cRNA found that potassium was transported better than ammonium, each of which was transported significantly better than sodium, criteria that are compatible with a role for HCN2 in ammonium transport. In microperfused rat outer medullary collecting duct segments, the initial rate of acidification, upon exposure to a basolateral ammonium chloride pulse, was higher in intercalated than in principal cells. A specific inhibitor of HCN2 (ZD7288) decreased acidification only in intercalated cells from control rats. In rats with chronic metabolic acidosis, the rate of acidification doubled in both intercalated and principal cells; however, ZD7288 had no significant inhibitory effect. Thus, HCN2 is a basolateral ammonium transport pathway of intercalated cells and may contribute to the renal regulation of body pH under basal conditions.

Induction of Metabolic Acidosis with Ammonium Chloride (NH4Cl) in Mice and Rats – Species Differences and Technical Considerations

Ammonium chloride addition to drinking water is often used to induce metabolic acidosis (MA) in rodents but may also cause mild dehydration. Previous microarray screening of acidotic mouse kidneys showed upregulation of genes involved in renal water handling. Thus, we compared two protocols to induce metabolic acidosis in mice and rats: standard 0.28M NH₄Cl in drinking water or an equivalent amount of NH₄Cl in food. Both treatments induced MA in mice and rats. In rats, NH ₄Cl in water caused signs of dehydration, reduced mRNA abundance of the vasopression receptor 2 (V2R), increased protein abundance of the aquaporin water channels AQP2 and AQP3 and stimulated phosphorylation of AQP2 at residues Ser256 and Ser261. In contrast, NH₄Cl in food induced massive diuresis, decreased mRNA levels of V2R, AQP2, and AQP3, did not affect protein abundance of AQP2 and AQP3, and stimulated phosphorylation at Ser261 but not pSer256 of AQP2. In mice, NH₄Cl in drinking water stimulated urine concentration, increased AQP2 and V2R mRNA levels, and enhanced AQP2 and AQP3 protein expression with higher levels of AQP2 pSer256 and pSer261. Addition of NH₄Cl to food, stimulated diuresis, had no effect on mRNA levels of AQP2, AQP3, and V2R, and enhanced only AQP3 protein abundance whereas pSer256-AQP2 and pSer261-AQP2 remained unaltered. Similarly, AQP2 staining was more intense and luminal in kidney from mice with NH₄Cl in water but not in food. Pendrin, SNAT3 and PEPCK mRNA expression in mouse kidney were not affected by the route of N₄Cl application. Thus, addition of NH₄Cl to water or food causes MA but has differential effects on diuresis and expression of mRNAs and proteins related to renal water handling. Moreover, mice and rats respond differently to NH₄Cl loading, and increased water intake and diuresis may be a compensatory mechanism during MA. It may be necessary to consider these effects in planning and interpreting experiments of NH₄Cl supplementation to animals.

Acute and chronic metabolic acidosis interferes with aquaporin-2 translocation in the rat kidney collecting ducts

Renal aquaporin-2 (AQP2) expression plays a key role in urine concentration. However, it is not known whether metabolic acidosis affects urine-concentrating ability through AQP2 expression in the kidney and urine. We examined urinary excretion and renal expression of AQP2 in control and acidosis rats, using RT-competitive PCR, immunoblot and immunocytochemistry. Urinary excretion of AQP2 is decreased by 92% even with the increase in AQP2 mRNA and protein expressions in the collecting ducts by metabolic acidosis in rats. Urine osmolality in control rats was 1670+/-198 mOsm per kg H(2)O, and immunocytochemistry revealed the presence of AQP2 in the apical plasma membrane of the principal cells in the collecting ducts. Urine osmolality in acidosis rats was lower than that in control (1397+/-243 mOsm per kg H(2)O), and immunocytochemistry showed the diffuse presence of AQP2 in the cytoplasm of the principal cells. Differential centrifugation-coupled immunoblot showed a significant decrease in the ratio of AQP2 in plasma membrane-enriched fraction to that in intracellular vesicle-enriched fraction by metabolic acidosis. In summary, AQP2 translocation is largely decreased by metabolic acidosis even with increased expression in the collecting ducts. A disorder of AQP2 translocation in the collecting ducts with acidosis may be responsible for the diuresis in patients with chronic renal failure.

Excess Casein in the Diet Is Not the Unique Cause of Low-Grade Metabolic Acidosis: Role of a Deficit in Potassium Citrate in a Rat Model

This study examined the effects of a dietary model of protein excess and K anion salt deficit on the occurrence of metabolic acidosis in rat. Rats were adapted to diets containing either 13 or 26% casein, together with mineral imbalance, through lowering K/increasing sodium/omitting alkalinizing anions. For each protein level, a group of rats was supplemented with K citrate. Dietary K citrate resulted in neutral urinary pH, whatever the protein level. Urea excretion was higher in rats adapted to 26% casein than 13% casein diets, but K citrate enhanced this excretion and suppressed ammonium elimination. No citraturia could be observed in acidotic rats, whereas K citrate greatly stimulated citraturia and 2-ketoglutarate excretion. In conclusion, low-grade metabolic acidosis can occur with a moderate protein level in the diet. K citrate was apparently less effective in rats adapted to the 26% casein level than in those adapted to the 13% casein level with regard to magnesium, citrate and 2-ketoglutarate concentrations in urine.

Regulation of expression of the SN1 transporter during renal adaptation to chronic metabolic acidosis in rats.

During chronic metabolic acidosis, renal glutamine utilization increases markedly. We studied the expression of the system N1 (SN1) amino acid transporter in the kidney during chronic ammonium chloride acidosis in rats. Acidosis caused a 10-fold increase in whole kidney SN1 mRNA level and a 100-fold increase in the cortex. Acidosis increased Na(+)-dependent glutamine uptake into basolateral and brush-border membrane vesicles (BLMV and BBMV, respectively) isolated from rat cortex (BLMV, 219 +/- 66 control vs. 651 +/- 180 pmol. mg(-1). min(-1) acidosis; BBMV, 1,112 +/- 189 control vs. 1,652 +/- 148 pmol. mg(-1). min(-1) acidosis, both P < 0.05). Na(+)-independent uptake was unchanged by acidosis in BLMV and BBMV. The acidosis-induced increase in Na(+)-dependent glutamine uptake was eliminated by histidine, confirming transport by system N. SN1 protein was detected only in BLMV and BBMV from acidotic rats. After recovery from acidosis, SN1 mRNA and protein and Na(+)-dependent glutamine uptake activity rapidly returned to control levels. These data provide evidence that regulation of expression of the SN1 amino acid transporter is part of the renal homeostatic response to acid-base imbalance.

Metabolic acidosis in rats increases intestinal NHE2 and NHE3 expression and function.

Chronic metabolic acidosis increases intestinal Na absorption, although through undefined mechanisms. Whether this occurs through enhanced expression and/or function of the brush-border Na+/H+ exchangers (NHE)2 and NHE3 is unknown. Metabolic acidosis was induced in rats by feeding ammonium chloride through their drinking water. Intestinal NHE activities were measured using brush-border 22Na+ uptake. Western and Northern blots measured changes in protein and mRNA expression, respectively. Acidosis occurred within 2 days of ammonium chloride feedings but increased after 6 days. NHE2 and NHE3 activities, protein expression, and mRNA levels increased in acidotic rats compared with controls. In contrast, basolateral NHE1 expression was not affected. Brush-border alkaline phosphatase showed no effect of metabolic acidosis on cellular differentiation. This study demonstrated a direct effect of metabolic acidosis on NHE2 and NHE3 activity, expression, and gene transcription. Metabolic acidosis is one of the few circumstances shown to affect NHE2 function and expression, thus providing insights into the role of NHE2 on intestinal physiology.

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Bone histomorphometric changes due to differences in calcium intake under metabolic acidosis in rats.

Effects of differences in calcium (Ca) intake on bone metabolism under metabolic acidosis were examined by bone histomorphometry in rats. Rats were divided into 5 diets; low Ca (0.02%) diet (LCD), moderate low Ca (0.3%) diet (LmCD), standard Ca (0.62%) diet (SCD), moderate high Ca (1%) diet (HmCD) and high Ca (3%) diet (HCD). Each diet rats were subdivided into the acidotic group given a 1.8% ammonium chloride solution as drinking water and control group given deionized water. Blood and double labeled bone were collected 30 days later. Arterial blood pH was significantly lower, and plasma ionized Ca level and urinary Ca excretion were higher in the acidotic groups than those in the control groups in all diets. Breaking force in femur and bone volume in tibial proximal metaphysis were significantly lower in the acidotic groups than those in the control groups in LCD, LmCD and SCD. In the acidotic groups, osteoid thickness was significantly higher in LCD than that in LmCD, HmCD and HCD. Mineral apposition rate in the acidotic groups was significantly higher in LCD and LmCD than that in HmCD and HCD. These results suggest that bone mineral loss and bone fragility under metabolic acidosis may be accelerated by high turnover of bone metabolism due to insufficient dietary Ca intake, but can be prevented by adequate supplementation of Ca.

Effects of Inhibition of Phosphoenolpyruvate Carboxykinase on Ammonia Production by the Rat Kidney

Phosphoenolpyruvate carboxykinase (PEPCK) in the renal cortex shows the expected increase in activity but oxal acetate decarboxylase and malic enzyme, two other enzymes capable of providing precursors for use in the total oxidation of glutamine by the kidney, showed no change in their activity as a result of metabolic acidosis in rats. 3-Mercaptopicolinic acid, a substance which inhibits PEPCK, caused a 23% decrease in the oxidation of glutamine to CO&lt;sub&gt;2&lt;/sub&gt; by kidney cortical slices &lt;i&gt;in vitro. &lt;/i&gt;3-Mercaptopicolinic acid &lt;i&gt;in vivo &lt;/i&gt;had anomalous effects on gluconeogenesis but consistently inhibited ammoniagenesis by kidneys of normal as well as acidotic rats.