Preventive effect of phosphoenolpyruvate on hypoxemia induced by oleic acid in Guinea pigs.

Oleic acid-induced hypoxemia is an animal model of acute respiratory distress syndrome (ARDS). Increased capillary permeability is a cause of hypoxemia in lung injury. Endothelial cells form a major capillary barrier, and disruption of the barrier appears to involve a decreased level of ATP in the cells. Phosphoenolpyruvate (PEP) is an endogenous substance that is one of the ATP precursors and can cross some cell membranes via anion exchanger. We examined the effect of PEP on oleic acid-induced lung injury in guinea pigs. An intravenous injection of oleic acid (15 microl/kg) caused severe hypoxemia. Pretreatment with PEP at a dose of 2, 20, or 200 micromol/kg attenuated the oleic acid-induced decrease in the arterial partial pressure of oxygen in a dose-dependent manner. Furthermore, PEP attenuated the oleic acid-induced increase in vascular permeability in the proximal and distal bronchi, as indicated by the extravascular leakage of Evans Blue dye. The combination of PEP with ATP (4 micromol/kg) showed no additional inhibitory effect on oleic acid-induced lung injury, compared with PEP alone. We suggest that PEP is a promising candidate to prevent hypoxemia in acute lung injuries associated with increased vascular permeability, such as ARDS.

Phosphoenolpyruvate prevents the decline in hepatic ATP and energy charge after ischemia and reperfusion injury in rats.

BACKGROUND: Phosphoenolpyruvate (PEP) is a high-energy metabolite in the final step of glycolysis. PEP is converted into pyruvate by pyruvate kinase. One molecule of adenosine triphosphate (ATP) is generated from one molecule of PEP. The aim of this study was to examine the effects of PEP on hepatic energy metabolism at an early phase after ischemia and reperfusion were examined in rats. MATERIALS AND METHODS: Male Wistar rats (250-350 g) were divided into two groups; after two 15-min periods of ischemia with 2 min reperfusion in between, either PEP or glucose solution (400 mmol/liter, pH 7.4) was infused into the portal vein (2.5 ml/300 g body wt/5 min). Before and 0, 5, 10, and 30 min after ischemia, arterial blood and liver tissue were collected for analyses. RESULTS: During the two ischemic periods, ATP and total adenine nucleotide (TAN) of the liver decreased from 9.10 +/- 0.50 and 14.06 +/- 0.29 to 0.99 +/- 0.50 and 10.86 +/- 0.42 mmole/g liver, respectively (P < 0.05), while adenosine monophosphate (AMP) increased from 1.18 +/- 0.15 to 8.47 +/- 0.66 mmole/g liver (P < 0. 05). Hepatic energy charge (EC) significantly decreased from 0.78 +/- 0.02 to 0.16 +/- 0.03 (P < 0.05). Serum concentrations of pyruvate and lactate were elevated from 1.18 +/- 0.15 and 18.4 +/- 0. 52 to 3.29 +/- 0.52 and 72.6 +/- 4.8 mg/dl, respectively (P < 0.05). After a 5-min infusion of PEP or glucose solution, the ATP concentration was significantly higher in the PEP group than in the glucose group (4.08 +/- 0.58 micromole/g liver vs 2.20 +/- 0.45 micromole/g liver, P < 0.01), whereas AMP concentration was significantly lower in the PEP group than in the glucose group (4.26 +/- 0.66 micromole/g liver vs 7.02 +/- 0.71 micromole/g liver, P < 0. 01). EC in the PEP group was significantly higher than that in the glucose group (0.493 +/- 0.051 vs 0.293 +/- 0.042, P < 0.01). Ten minutes after ischemia, the ATP, TAN, and EC levels were still higher in the PEP group than in the glucose group, but the difference did not reach statistical significance. At 30 min after ischemia, these values became similar in both groups. At 5, 10, and 30 min after ischemia, serum pyruvate concentrations were higher in the PEP group than in the glucose group. CONCLUSION: These findings suggest that PEP recovers hepatic energy from liver cell damage at an early phase after ischemia and reperfusion by prompt ATP production through the degradation of PEP into pyruvate in the liver.

Phosphoenolpyruvate/adenosine triphosphate enhances post-ischemic survival of skeletal muscle.

This study examined whether ischemia-reperfusion injury to skeletal muscle could be reduced by post-ischemic infusion of phosphoenolpyruvate (PEP) and adenosine triphosphate (ATP). The rectus femoris muscle of 54 rabbits was rendered ischemic for 3.5 hr. Eighteen rabbits received no further treatment. Thirty-six were infused intra-arterially at the end of ischemia, 18 with vehicle alone, and 18 with a mixture of PEP (80 mumol/kg) and ATP (2.6 mumol/kg). Six rabbits from each group were explored after 24 hr reperfusion and the muscles assessed for viability (by nitro blue tetrazolium), ATP (by luciferin-luciferase chemiluminescence), malonyldialdehyde (MDA) (thiobarbituric acid method), and water content. The remaining muscles in each group were examined histologically after either 1 hr or 4 days of reperfusion. At 24 hr the viability of the PEP/ATP infused muscles (78.9 +/- 15.4 percent) was significantly greater than that of untreated (41.4 +/- 27.3 percent) or vehicle-infused groups (34.0 +/- 32.7 percent). ATP stores were significantly higher and MDA (indicative of free radical activity) and water content significantly lower in the PEP/ATP treated group. At 24 hr and 4 days, muscles infused with PEP/ATP showed less necrosis and fewer infiltrating neutrophils than the untreated groups. Studies with isolated rabbit neutrophils showed that ATP alone significantly inhibited superoxide anion production by stimulated neutrophils. However, when combined with PEP at concentrations similar to those achieved in vivo, ATP did not significantly affect superoxide production. The findings indicate that post-ischemic infusion of PEP/ATP significantly reduces ischemia-reperfusion injury in rabbit skeletal muscle. The protective effect of PEP/ATP is more likely to be due to supplementation of intracellular ATP stores than to the inhibition of superoxide production by infiltrating neutrophils.

[The effect of fructose-1,6-diphosphate and phosphoenolpyruvate on the course of early occlusion and reperfusion arrhythmias in rats]. / Vliianie fruktozo-1,6-difosfata i fosfoenolpiruvata na techenie rannikh okkliuzionnykh i reperfuzionnykh aritmii u krys.

Fructose-1,6-diphosphate (150 and 50 mg/kg) and phosphoenolpyruvate (0.5 and 0.1 mg/kg) decreased the development of ventricular tachycardia, ventricular fibrillation and the intensity of ventricular extrasystoles after coronary occlusion in experimental rats. Both compounds were active as anti-fibrillation agents on reperfusion arrhythmias. Fructose-1,6-diphosphate potentiated the effect of lidocaine.

Clinical application of phosphoenolpyruvate (PEP) to autologous transfusion of patients with open heart surgery.

Patients undergoing surgery for cardiac valve replacement were autologously transfused after their cryopreserved blood was treated with phosphoenolpyruvate. Five patients received red cells treated on the day of operation with a solution containing phosphoenolpyruvate, the other 6 serving as a control group. None of the patients received homologous blood. The treated red cells had a normal adenosine triphosphate concentration; in the control group a 10% decrease was noted. The 2,3-bisphosphoglycerate concentration was 211% of normal in red cells of the treated group and 69% of normal in the control group. The P50 values (mmHg) were 31.1 +/- 3.5 (treated), 20.3 +/- 1.7 (untreated), and 26.1 +/- 0.6 (fresh, not cryopreserved), respectively. Both the 2,3-bisphosphoglycerate and P50 values of the circulating blood were significantly (p < 0.02) increased in the patients receiving treated red cells. The increase in the 2,3-bisphosphoglycerate and P50 remained for 6 hours after transfusion at which time the levels of the 2,3-bisphosphoglycerate were 14.5 +/- 2.2 mumol/gHb (treated group) and 10.5 +/- 0.8 mumol/gHb (control group). Those of P50 were 28.1 +/- 1.5 mmHg (treated group) and 25.9 +/- 0.9 mmHg (control group). The adenosine triphosphate levels were not significantly different. The postoperative values of pH and hematocrit did not differ between the two groups. It was estimated that the oxygen delivery capacity in the circulating blood was about 30% higher in the patients receiving phosphoenolpyruvate treated blood than in those receiving untreated blood.

[The effect of phosphoenolpyruvate on the course of the acute period in experimental myocardial infarct]. / Vliianie fosfoenolpiruvata na techenie ostrogo perioda éksperimental'nogo infarkta miokarda.

It was found in the experiments on dogs, that phosphoenolpyruvate decreased the level of regional metabolic acidosis, stabilized energy metabolism, cardiohemodynamics and enhanced the blood supply of the ischemic myocardium. Anti-ischemic effect of the phosphoenolpyruvate was more significant in comparison with fructose-1,6-diphosphate in isomolar doses.

Factors involved in salvaging ischaemic rabbit skin flaps: ATP and free radicals but not thromboxane.

Rabbit epigastric free flaps were subjected to ischaemia at 25 degrees C for 24 hours. At the time of revascularisation the flaps were infused intra-arterially with one of the following: Hanks balanced salt solution (control), the high energy phosphates PEP/ATP, the thromboxane synthetase inhibitor dazoxiben hydrochloride, the free radical scavenger SOD and a combination of all these agents (treated groups). Control ischaemic flap survival at post-ischaemia day 7 was 23.5%, while the other treatments resulted in improved flap survival of 43.5% (p less than 0.025), 23.5% (not significant), 38.6% (p less than 0.05) and 35.7% (p less than 0.05) respectively. None of these agents improved post-ischaemic blood flow significantly. These results would support the use of PEP/ATP or SOD in the clinical treatment of failing ischaemic skin flaps but do not support the use of dazoxiben hydrochloride.

[The action of pyruvate kinase and phosphoenolpyruvate on the development of experimental thrombosis]. / Vliianie piruvatkinazy i fosfoenolpiruvata na formirovanie eksperimental'nogo tromboza.

Tests set up on rats and rabbits showed the ability of phospho-enolpyruvate and pyruvate-kinase to lower the aggregation of thrombocytes and prevent formation of experimental microthrombosis. The joint introduction of these compounds in most experiments resulted in potentiation of the antithrombotic effect.