Administration of ATP-MgCl2 after trauma-hemorrhage and resuscitation restores the depressed cardiac performance

The role of the mitochondrion in trauma and shock

The mitochondrion of the eukaryotic cell is well known as a "power plant" whose energy is made available via the high-energy phosphate bonds of ATP. This indispensable and superbly adapted organelle appears to have originated as an endosymbiotic bacterium rather than as a eukaryotic creation per se. However, under the dangerous conditions of trauma and shock, the mitochondrion can become destabilized and harm its host cell in a variety of ways. These contrary traits may be, in part, vestiges from the bacterial origins of mitochondria. The mitochondrion can respond to the stress of trauma and shock by opening pores that leak contents into the host cell's cytoplasm, an event that can trigger programmed cell death or necrosis. In addition, the enormous oxygen consumption by mitochondria presents a two-edged sword in that a deranged mitochondrion can produce reactive oxygen species that damage genes and gene products, inflicting considerable harm to the mitochondrion and its host cell. However, although trauma and shock can cause the mitochondrion to wreak havoc in many ways, an adjuvant intervention with exogenous ATP-MgCl2 after trauma and shock appears useful for reducing cell and organ damage under those conditions.

Effects of infusion of adenosine triphosphate-magnesium chloride on cardiopulmonary and clinicopathologic variables, cytokine activity, and endothelin concentration in horses administered a low dose of endotoxin

OBJECTIVE

To evaluate systemic effects of i.v. infusion of ATP-MgCl2 subsequent to infusion of a low dose of endotoxin in horses.

ANIMALS

12 adult horses.

PROCEDURE

Horses were administered endotoxin (lipopolysaccharide [LPS]) or saline (0.9% NaCl) solution i.v., during a 30-minute period. Immediately thereafter, horses in each group were infused i.v. with ATP-MgCl2 or saline solution. Two weeks later, horses were administered the opposite solution (LPS or saline solution), but it was followed by the same infusion as 2 weeks previously (ie, ATP-MgCl2 or saline solution). Cardiopulmonary and clinicopathologic variables, cytokine activity, and endothelin (ET) concentrations were recorded.

RESULTS

IV infusion of ATP-MgCl2 after administration of a low dose of endotoxin failed to attenuate the cardiopulmonary, clinicopathologic, and cytokine alterations that develop secondary to endotoxin exposure. The combination of LPS and ATP-MgCl2 potentiated pulmonary hypertension, leukopenia, and neutropenia when compared with the combination of LPS and saline solution. The combination of LPS and ATP-MgCl2 resulted in thrombocytopenia. Endothelin concentration was increased in jugular venous and pulmonary arterial plasma in horses receiving LPS and ATP-MgCl2. Similar increases were not observed with LPS and saline solution.

CONCLUSIONS AND CLINICAL RELEVANCE

Administration of ATP-MgCl2 did not protect horses from systemic effects of experimentally induced endotoxemia. Furthermore, the use of ATP-MgCl2 during endotoxemia may worsen the cardiopulmonary and clinicopathologic status of affected horses. Because ATP and other adenine nucleotides are released from cells during shock, their potential role in the development of hemodynamic derangements, leukocyte adherence, and coagulopathies during endotoxemic episodes warrants further investigation.

Metabolic disturbances in shock, and the role of ATP-MgCl2 and sex steroids

Hemorrhage following accidental injuries is a common cause of death in the industrialized world. Moreover, the impact of elective surgery and solid organ transplantation sometimes results in low flow conditions similar to those seen following hemorrhagic shock. A shortage in O(2) availability, or hypoxia, leads to sequential changes in cell metabolism and morphology, including inflammatory responses and the expression of hypoxia-inducible transcription factor-1, which controls the cellular adaptation to hypoxia. These endogenous adaptive responses show that O(2) deprivation is not an unforeseen event for cells. The purpose of this review article is to discuss the pathophysiologic principles of shock and the metabolic alterations that cells undergo during low flow conditions. Moreover, the rationale for therapeutic intervention by administering ATP-MgCl(2) and sex steroids following shock and trauma will also be discussed.

Adenosine triphosphate-magnesium dichloride during hyperdynamic porcine endotoxemia: effects on hepatosplanchnic oxygen exchange and metabolism

OBJECTIVE

To assess the effects of adenosine triphosphate-magnesium dichloride (ATP-MgCl2) on systemic and hepatosplanchnic hemodynamics, oxygen exchange, and energy metabolism over 24 hrs of hyperdynamic normotensive porcine endotoxemia.

DESIGN

Prospective, randomized, controlled experimental study with repeated measures.

SETTING

Investigational animal laboratory.

SUBJECTS

Seventeen pigs were divided into two groups: eight animals receiving endotoxin served as a control group and nine animals received endotoxin (lipopolysaccharide) and ATP-MgCl2.

INTERVENTIONS

Pigs were anesthetized, mechanically ventilated, and instrumented. Endotoxemia was achieved by continuous intravenous infusion of Escherichia coli lipopolysaccharide. Animals were resuscitated by hetastarch targeted to maintain mean arterial pressure of >75 mm Hg. Twelve hours after the start of the endotoxin infusion, ATP-MgCl2, or its vehicle, were administered for 12 hrs.

MEASUREMENTS AND MAIN RESULTS

Mean arterial pressure was maintained in the control group because of a sustained increase in cardiac output achieved by fluid resuscitation, whereas ATP-MgCl2 significantly decreased mean arterial pressure because of further systemic vasodilatation. ATP-MgCl2 markedly increased portal venous flow. In contrast to the controls, hepatic arterial flow remained unchanged until the end of the experiment, despite the further increase in cardiac output. The ileal mucosal-arterial PCO2 gap (Delta PCO2) progressively increased (p <.05) in control animals, whereas it was restored to prelipopolysaccharide levels during ATP-MgCl2 infusion. Changes in Delta PCO2 correlated with those of portal vein blood flow in these animals (r = -.68, p <.05). Moreover, ATP-MgCl2 blunted the lipopolysaccharide-induced decrease in hepatic lactate balance but did not affect portal venous pH, hepatosplanchnic oxygen exchange, splanchnic lactate/pyruvate ratios, isoprostane, NO2- + NO3-, cytokine concentrations, or tissue nucleotide content.

CONCLUSION

During long-term hyperdynamic porcine endotoxemia, ATP-MgCl2 normalized the otherwise progressive rise of the ileal mucosal-arterial Delta PCO2. Furthermore, it allowed blunting of the continuous decrease in hepatic lactate clearance, thus preserving the metabolic coupling between lactate release from the intestine and lactate utilization by the liver.

Alterations in systemic and local colonic hemodynamic variables associated with intravenous infusion of ATP-MgCl2 in healthy anesthetized horses

OBJECTIVE

To characterize alterations in systemic and local colonic hemodynamic variables associated with IV infusion of ATP-MgCl2 in healthy anesthetized horses.

ANIMALS

12 adult horses.

PROCEDURE

Six horses were given ATP-MgCl2, IV, beginning at a rate of 0.1 mg of ATP/kg of body weight/min with incremental increases until a rate of 1.0 mg/kg/min was achieved. The remaining 6 horses were given an equivalent volume of saline (0.9% NaCl) solution over the same time period. Colonic and systemic hemodynamic variables and colonic plasma nitric oxide (NO) concentrations were determined before, during, and after infusion.

RESULTS

Infusion of ATP-MgCl2 caused a rate-dependent decrease in systemic and colonic vascular resistance, principally via its vasodilatory effects. A rate of 0.3 mg of ATP/kg/min caused a significant decrease in systemic and colonic arterial pressure and colonic vascular resistance without a significant corresponding decrease in colonic arterial blood flow. Consistent alterations in NO concentrations of plasma obtained from colonic vasculature were not detected, despite profound vasodilatation of the colonic arterial vasculature.

CONCLUSIONS AND CLINICAL RELEVANCE

Results revealed that IV infusion of ATP-MgCl2 may be beneficial in maintaining colonic perfusion in horses with ischemia of the gastrointestinal tract, provided a sufficient pressure gradient exists to maintain blood flow.

Exogenous Mg-ATP induces a large inhibition of pyruvate kinase in intact rat hepatocytes

Mg-ATP infusion in vivo has been reported to be beneficial both to organ function and survival rate in various models of shock. Moreover, a large variety of metabolic effects has been shown to occur in several tissues due to purinergic receptor activation. In the present work we studied the effects of exogenous Mg-ATP in rat liver cells perifused with dihydroxyacetone to investigate simultaneously gluconeogenetic and glycolytic pathways. We found a significant effect on oxidative phosphorylation as characterized by a decrease in oxygen consumption rate and in the cellular ATP-to-ADP ratio associated with an increase in lactate-to-pyruvate ratio. In addition, exogenous Mg-ATP induced rapid and reversible inhibition of both gluconeogenesis and glycolysis. The main effect on gluconeogenesis was located at the level of the fructose cycle, whereas the decrease in glycolysis was due to a strong inhibition of pyruvate kinase. Although pyruvate kinase inhibition induced by exogenous Mg-ATP was allosteric when assessed in vitro after enzyme extraction, we found a large decrease in the apparent maximal velocity when kinetics were assessed in vivo in intact perifused hepatocytes. This newly described short-term regulation of pyruvate kinase occurs only in the intact cell and may open new potentials for the pharmacological regulation of pyruvate kinase in vivo.

Salutary effects of ATP-MgCl2 on the depressed endothelium-dependent relaxation during hyperdynamic sepsis

OBJECTIVES

Studies have shown that endothelium-dependent relaxation (mediated by endothelium-derived nitric oxide) is depressed during the early, hyperdynamic stage of sepsis. Although it is known that ATP-MgCl2 produces beneficial effects following various adverse circulatory conditions, it remains unknown whether this agent attenuates the depressed endothelium-dependent relaxation during early sepsis. The aim of this study, therefore, was to determine whether or not the administration of ATP-MgCl2 early after the onset of sepsis improves or maintains endothelium-dependent relaxation.

DESIGN

Prospective, controlled animals study.

SETTING

A university research laboratory.

SUBJECTS

Adult male Sprague-Dawley rats were subjected to polymicrobial sepsis by cecal ligation and puncture (CLP), followed by administration of 3 mL/100 g body weight normal saline to these and sham-operated rats.

INTERVENTIONS

At 1 hr after CLP, ATP-MgCl2 (50 micromol/kg body weight) or an equivalent volume of normal saline was infused intravenously over 90 mins.

MEASUREMENTS AND MAIN RESULTS

At 5 hrs or 10 hrs after CLP (i.e., the early, hyperdynamic stage of sepsis), the thoracic aorta was isolated, cut into rings, and placed in organ chambers. Norepinephrine was used to preconstrict vessel rings. Dose responses for an endothelium-dependent vasodilator, acetylcholine (ACh, via endothelium-dependent nitric oxide), and an endothelium-independent vasodilator, nitroglycerin, were determined. These results indicate that endothelium-dependent relaxation induced by ACh was significantly depressed at 5 and 10 hrs after CLP. Administration of ATP-MgCl2 after the onset of sepsis, however, maintained ACh-induced vascular relaxation. In contrast, no significant difference in nitroglycerin-induced vascular relaxation as well as norepinephrine-induced contraction was observed, irrespective of administration of ATP-MgCl2.

CONCLUSION

Since administration of ATP-MgCl2 prevents the impaired vascular relaxation to the endothelium-dependent vasodilator ACh, this agent may be a useful adjunct for maintaining endothelial cell function during the hyperdynamic stage of sepsis.