Effects Of Sodium Pyruvate On Ameliorating Metabolic Acidosis

Metabolic acidosis, a common acid-base disorder, is associated with highmorbidity and mortality. Lactic acidosis, ketoacidosis, hyperchloremic acidosis, renaltubular acidosis and other acidosis caused by methanol, aethylenum or salicylateintoxication are the main types of metabolic acidosis in clinic. Metabolic acidosis hasmany depressive effects on myocardial function, cardiovascular function, facilitationof cardiac arrhythmias, stimulation of inflammation, and even leading to sudden death.Sodium bicarbonate (SB) therapy is the primarily supportive measure to metabolicacidosis in clinic, when the therapies tailored to the specific disorder are failure.However, the rationale for using SB to treat metabolic acidosis has been debated forseveral years. It is reported that SB can cause serious complications includingintracellular pH (pHi) decline, hypercapnia and hypernatraemia. SB is forbidden totreat respiratory acidosis and metabolic acidosis with ventilation function injury.Tris-hydroxymethyl aminomethane (THAM) therapy can depress breathing, decreaseblood pressure, result in hypokalemia and ventricular fibrillation. As a result of thesecomplications, THAM is rarely used for the treatment of pediatric disordersassociated with metabolic acidosis or respiratory distress. Though alternative basebuffers have been developed, they all have potential adverse effects. Novel methodsshould be directed at improving both extracellular and intracellular acidosis.Sodium pyruvate (SP) is the ionic type of pyruvic acid. Pyruvate is anendogenous metabolic substrate and an effective ROS scavenger. Previous studieshave focused on the protective effects of SP on ameliorating multiple organ damageand in the animal models of hemorrhagic shock, ischemic-reperfusion and brain injurymodel. It is reported that SP can enhance survival rate and protect the function of vitalorgans, such as heart, brain, kidney, lung, liver and intestine. Morever, SP canameliorate lactic acidosis induced by hemorrhagic shock.Hemorrhagic shock reduced perfusion and hypoxia, cellular metabolic disorder，multiple organ dysfunction and leading to an accumulation of lactic acid. SP, knownas both an endogenous metabolic substrate and an effective ROS scavenger,ameliorates lactic acidisis by combined effects. SP infusion can restore blood flowand tissue oxygen supply. Meantime, SP has protective effect on organ function by itsanti-inflammatory and antioxidant effects. Morever, SP can regulate metabolism and consume intracellular hydrogen by its metabolism. Thus, it is not clear that theamelioration effect of SP on metabolic acidosis results from itself. Most of the workwhich suggests the correction effect of pyruvate on acidosis originates frompathological models such as hemorrhagic shock and dialysis. It is necessary toevaluate the effect of SP on other metabolic acidosis models.Ammonium chloride (NH4Cl)-induced hyperchloremic acidosis model is thecommon model of metabolic acidosis. It is very important to examine the effects ofSP on an NH4Cl-induced model of hyperchloremic acidosis. SP has a weak bufferingcapacity as the pKa of pyruvic acid is2.49. Morever, SP can consume intracellularhydrogen by its metabolism. Thus, we propose it works via consuming intracellularprotons in metabolic processes. It is very important to examine the effects of SP on anintracellular acidosis model.This study was designed to investigate the dose-dependent effects of SP onsystem hyperchloremic acidosis induced by NH4Cl in vivo and intracellular acidosisinduced by propionate in vitro. Then we evaluated the effects of sodium pyruvate onextracellular acidosis and intracellular acidosis.1. Establishment of NH4Cl-induced hyperchloremic acidosis rat modelTo investigate the influence of SP on hyperchloremic acidosis, it is necessary toestablish a hyperchloremic acidosis animal model. Marta Nowik induced metabolicacidosis rats medel by adminstered0.28mol/L NH4Cl (containing0.5%sucrose) indrinking water ad libitum for three days. The present study has optimized the MartaNowik method about NH4Cl-loading time. Model rats (Model group, n=10) wereadministered0.28mol/L NH4Cl (containing0.5%sucrose) in drinking water adlibitum. Rats were administered0.5%sucrose in drinking water ad libitum as Controlgroup (n=5). Zero, three and five days after NH4Cl loading, venous blood wascollected and analyzed immediately for pH, cHCO3-and base excess (BE).Three days after NH4Cl loading, no significant differences were observedbetween Model group and Control group in pH, cHCO3-and BE levels. Five daysafter NH4Cl loading, pH, cHCO3-and BE of Model group decreased compared withthe Control group (P<0.01), demonstrating that NH4Cl loading in drinking water for5days resulted in induction of metabolic acidosis. Morever, we find that there was apositive correlation between rats weight increment and pH five days after NH4Clloading. This suggest that rats weight increment may be a supplementary index toevaluate the severity of NH4Cl-induced hyperchloremic acidosis rat model.2. Effects of SP on ameliorating hyperchloremic acidosis in ratsWe evaluated effects of SP on an ammonium chloride (NH4Cl)-inducedhyperchloremic acidosis rat model. SP was infused at overall doses of2,4and6 mmol/kg for the SP1group, SP2group and SP3group, respectively. Treatment withsodium bicarbonate (SB) was used as a positive control (2mmol/kg), and treatmentwith normal saline (NS) was used as a volume control (2mL/kg). Blood was sampledfrom the ophthalmic venous plexus for pH, blood gases, electrolytes, glucose,creatinine and urea analysis after injection.Results showed that, the pH of SP1group showed no significant differencecompared with the NS group. The SP2and SP3group had a higher pH than the NSgroup (P<0.01).The SB group had a higher pH than the NS group (P<0.05). Moreover,the pH of SP group at T15was higher than it at T0(P<0.05). The pH of SB group at T15had a higher trendency compared with it at T0. The pH of SB group at T30was higherthan it at T0(P<0.05). The pH, cHCO3-and BE of SP1and SP2group had a tendency todecrease after T15, but was followed by a increase after T30. The SP3group had amarked amelioration of systemic acidosis that was sustained for240minutes afteradministration. The effect of SB on pH was most marked in the first thirty minutes butwas followed by a moderate decrease. SP treatment ameliorated the abnormality ofcalcium (P<0.05) and decreased the blood potassium levels (P<0.05). The SP3grouphad higher glucose levels than SP1group (P<0.05). No significant differences wereobserved between all the groups in the plasma creatinine and urea levels. Renalpathological section results showed that SP treatment would not aggravate the renalinjury in hyperchloremic acidosis rats.3. Effects of SP on ameliorating intracellular acidosisTo investigate the influence of SP on intracellular acidosis, it is necessary toestablish a method to detect pHi. In this study, pHi was fluorimetrically measuredusing a BCECF-AM method by a dual-excitation (488nm and445nm),single-emission (535nm) ratiometric technique. There was a positive correlationbetween BCECF emission ratio (R, R=F(Ex=488nm/Em=535nm)/F(Ex=445nm/Em=535nm)) andpHi.The effect of20mmol/L and30mmol/L sodium propionate loading on pHi inEA.hy926cells was detected. Results showed that after2min and3.5min sodiumpropionate loading, the R values were not significantly decreased in20mmol/L groupcompared with the Control group. But they decreased significantly in30mmol/Lgroup compared with the Control group (P<0.05).The intracellular acidosis modelinduced by30mmol/L sodium propionate was more stable than that induced by20mmol/L sodium propionate.30mmol/L sodium propionate was applied to induce intracellular acidosis inEA.hy926cells.33mmol/L,66mmol/L and100mmol/L SP was applied for the SP1group, SP2group and SP3group. NS addition was performed as negative controlgroup (NS group). The addition of NS had no effect on pHi, while the addition of SP caused a transient rise in pHi. The SP groups have a higher peak pHi than the NSgroup (P<0.05).In summary, in in vivo study, treatment with SP provided notable beneficialeffects on metabolic acidosis, and the effects were dose dependent. Morever, SP hadquicker response and longer duration than SB in ameliorating metabolic acidosis. Inin vitro study, the pHi increased immediately after the addition of SP in sodiumpropionate induced endothelial cell intracellular acidosis model. This study comfiredthat SP can ameliorate both the intracellular acidosis and extracellular acidosis.