Infusion Of ATP-MgCl2 Research Articles

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

To characterize alterations in systemic and local colonic hemodynamic variables associated with IV infusion of ATP-MgCl2 in healthy anesthetized horses. 12 adult horses. 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. 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. 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.

Hemodynamic and metabolic alterations associated with intravenous infusion of a combination of adenosine triphosphate and magnesium chloride in conscious horses

Abstract Objective To determine hemodynamic and metabolic effects of IV infusion of ATP-MgCl2 combination and maximal safe IV infusion rate in conscious horses. Animals 6 adult female horses. Procedure All horses received an IV infusion of ATP-MgCl2 combination, beginning at a rate of 0.05 mg of ATP/kg of body weight/min, which was increased by 0.05 mg/kg/min increments at 10-minute intervals until a rate of 1.0 mg/kg/min was achieved. Data were collected prior to the start of the infusion, at the end of each infusion rate, and at 15-minute intervals for the next hour after discontinuation of the infusion. Measured or calculated hemodynamic variables included cardiac output, cardiac index, heart rate, stroke volume, systemic and pulmonary arterial pressures, and systemic and pulmonary vascular resistances. Arterial blood gas tensions, CBC, plasma biochemical profiles, urine volume and specific gravity, and selected clinical signs of disease also were evaluated. Results Intravenous infusion of ATP-MgCl2 significantly increased cardiac output, decreased systemic vascular resistance, and caused mild pulmonary hypertension. Magnitude of the hemodynamic alterations was dependent on rate of infusion. Maximal safe infusion rate for these horses was 0.3 mg/kg/min. All horses became lethargic, and their appetites diminished during the infusion; 5 horses had mild signs of abdominal discomfort. Flank sweating was observed in all horses as infusion rate increased. Urine volume and specific gravity and hematologic, biochemical, and arterial blood gas alterations were detected during and after infusion. Conclusions and Clinical Relevance Intravenous administration of ATP-MgCl2 in healthy, conscious, adult horses caused various metabolic and hemodynamic alterations that were without appreciable detrimental effects. (Am J Vet Res 1999;60:1140–1147)

Hepatocellular Dysfunction after Severe Hypotension in the Absence of Blood Loss Is Associated with the Increased IL-6 and PGE2

Although hepatocellular dysfunction occurs following trauma and hemorrhagic shock, whether severe hypotension even in the absence of blood loss depresses hepatocellular function remains unknown. The aim of this study, therefore, was to determine whether chemically induced severe hypotension causes hepatocellular dysfunction and, if so, whether IL-6 and PGE2are associated with this dysfunction. To study this, hypotension was induced in adult male rats by intravenous infusion of a high dosage of ATP–MgCl2solution (3.2 ± 0.45 μmol/min/kg body wt) for 60 min. Blood pressure decreased from 108 ± 6 mm Hg to an average of 43 mm Hg during the infusion period and returned to normal levels immediately after the completion of ATP–MgCl2infusion. At 0 and 4 h after hypotension, hepatocellular function [i.e., maximum velocity of indocyanine green clearance (Vmax) and its efficiency (Km)] was measured using a fiberoptic catheter andin vivohemoreflectometer. Cardiac output was determined by dye dilution. Microvascular blood flow was assessed by laser Doppler flowmetry. Plasma levels of PGE2and IL-6 were measured by radioimmunoassay and bioassay, respectively. The results indicate that severe hypotension in the absence of any blood loss depresses hepatocellular function (i.e., decreasedVmaxandKm) despite stable cardiac output and hepatic perfusion at 0 and 4 h after the completion of hypotension. Moreover, severe hypotension resulted in significantly increased plasma levels of PGE2(only at 0 h) and IL-6. Thus, chemically induced severe hypotension in the absence of any blood loss, which does not significantly reduce cardiac output and hepatic perfusion, depresses hepatocellular function and upregulates IL-6 and PGE2production.

The use of P31 magnetic resonance spectroscopy to evaluate the effect of ATP-MgCl2 perfusion on the metabolism of rat skin island flaps.

Depleted levels of adenosine triphosphate (ATP) are described as one of the important causes of skin flap failure. This study evaluated the beneficial effects of intra-arterial perfusion of ATP-magnesium chloride (MgCl2) in ischemic neurovascular skin island flaps in the rat and observed the changes of the highenergy phosphate metabolite using phosphorus 31-(P31) magnetic resonance spectroscopy (MRS). The changes of ATP, phosphocreatine (PCr), and inorganic phosphate (Pi) were observed from P31 MRS and the ratios of each metabolite were compared. The extent of skin flap survival was assessed 7 days after operation using an image analyzer. The PCr/Pi ratio of the experimental group (ATP-MgCl2) was significantly different from the control group (balanced salt solution; p < 0.05). Furthermore, the infusion of ATP-MgCl2 (40.3%) significantly improved the area of flap survival compared to the control group (14.2%; p < 0.05). The ratios of PCr/Pi PCr/(PCr + Pi) correlated with the extent of flap survival, and correlation coefficients were 0.59 and 0.60, respectively. In conclusion, ATP-MgCl2 improved skin flap survival. We were able to assess the metabolic state of the ATP-MgCl2-perfused skin flap and found that PCr/Pi ratios correlated with flap survival.

Effects of ATP-magnesium chloride on the cardiopulmonary manifestations of group B streptococcal sepsis in the piglet.

Low dose ATP-MgCl2 is reported to cause selective pulmonary vasodilation during hypoxic and thromboxane mimetic-induced constriction. In addition, it has been shown to increase cardiac output and improve cellular function during circulatory shock. Based on these properties we hypothesized that ATP-MgCl2 might ameliorate the cardiopulmonary manifestations of sepsis secondary to group B streptococci (GBS). We studied 14 anesthetized, mechanically ventilated piglets who received a continuous infusion of GBS (7.5 x 10(7) colony-forming units/kg/min) and were randomly assigned to a treatment group that received a continuous infusion of ATP-MgCl2 at 0.6 mumol/kg/min or a control group that received normal saline as placebo. Comparison of the hemodynamic measurements, pulmonary mechanics, and arterial blood gases over the first 120 min of ATP-MgCl2 infusions with those of the control group revealed the following: GBS infusion caused significant increases in mean pulmonary artery pressure, pulmonary vascular resistance (PVR), mean systemic arterial blood pressure, systemic vascular pressure (SVR), and PVR/SVR ratio with decreases in cardiac output and stroke volume. ATP-MgCl2 caused significant reduction in mean pulmonary artery pressure (p < 0.001), PVR (p < 0.0001), mean systemic arterial blood pressure (p < 0.003), SVR (p < 0.01), and PVR/SVR ratio (p < 0.03) with improvement in cardiac output (p < 0.001) and stroke volume (p < 0.01). The partial pressure of arterial O2 (p < 0.04), and pH (p < 0.001) were higher and the partial pressure of arterial CO2 (p < 0.02) lower in ATP-MgCl2-treated animals. Also dynamic lung compliance was higher (p < 0.001) and pulmonary airway resistance lower (p < 0.001) in treated animals. Median survival in control animals was 153 min, whereas all treated animals survived to 240 min (p < 0.001). These data demonstrate that ATP-MgCl2 ameliorates the deleterious cardiopulmonary manifestations of GBS sepsis and results in improved survival in a young animal model.

Estimation of renal interstitial adenosine and purine metabolites by microdialysis.

It has been proposed that adenosine, derived from ATP and released into the renal interstitium, mediates a reduction in renal function in ischemic acute renal failure. Because no direct measurements of interstitial adenosine are available, we evaluated an in vivo microdialysis technique to assess the levels of adenosine and its metabolites in the cortex of the normal rat kidney (n = 6). Microdialysis probe implantation did not alter cortical renal blood flow, glomerular filtration rate, or fractional sodium excretion. The interstitial concentration of adenosine was 199 +/- 53 nM, and relative concentrations of inosine, hypoxanthine, xanthine, and uric acid were 99 +/- 47, 182 +/- 29, and 183 +/- 70 nM and 1.8 +/- 0.4 microM, respectively. Infusion of ATP-MgCl2 (n = 5) resulted in a significant increase in the dialysate levels of adenosine (67 +/- 11 to 378 +/- 97 nM), inosine (230 +/- 102 to 803 +/- 219 nM), and uric acid (3.5 +/- 1.3 to 6.9 +/- 1.7 microM). In conclusion, this study demonstrates that the microdialysis technique is suited to monitor metabolically important substances in the renal interstitium.

ATP-MgCl2 administration normalizes macrophage cAMP and beta-adrenergic receptors after hemorrhage and resuscitation.

Although ATP-MgCl2 attenuates the release of inflammatory cytokines and restores the defective macrophage (M phi) antigen presentation function after hemorrhage and resuscitation, it is not known whether administration of this agent after hemorrhage affects M phi adenosine 3',5'-cyclic monophosphate (cAMP) levels and beta-adrenergic receptors. To determine this, rats underwent a midline laparotomy (i.e., induction of trauma) and were then bled to and maintained at a mean arterial pressure of 40 mmHg until 40% of maximum bleedout volume was returned in the form of Ringer lactate (RL). Animals were resuscitated with four times the volume of shed blood with RL, during and after which ATP-MgCl2 (50 mumol/kg) or saline was administered over 95 min. At 1.5 h postresuscitation (i.e., 10 min after completion of ATP-MgCl2 infusion), peritoneal M phi and Kupffer cells were isolated, and cAMP levels were measured by radioimmunoassay. beta-Receptor binding characteristics were also determined in isolated Kupffer cells. The results indicate that cAMP levels increased significantly in both peritoneal M phi and Kupffer cells after hemorrhage and resuscitation. Maximum binding capacity (Bmax) of beta-receptors increased in Kupffer cells, suggesting that the elevated cAMP may be due to the increased beta-receptor Bmax under such conditions. ATP-MgCl2 treatment, however, markedly decreased beta-receptor Bmax in Kupffer cells and cAMP in both peritoneal M phi and Kupffer cells, and the values were similar to shams. Thus normalization of M phi cAMP levels and beta-receptor binding capacity by ATP-MgCl2 may contribute to the immunoenhancing effects of this agent observed after trauma-hemorrhage and fluid resuscitation.

ATP-MgCl2 treatment after trauma-hemorrhage/resuscitation increases hepatocyte P2-purinoceptor binding capacity.

Although our studies indicate that P2-purinoceptor binding capacity decreases after hemorrhage and resuscitation, it is not known whether ATP-MgCl2 administration after hemorrhage has any beneficial effects on the receptor dynamics. To study this, we performed laparotomy (i.e., trauma induced) on rats and bled them to and maintained them at a mean arterial pressure of 40 mmHg until 40% of maximum bleedout volume was returned in the form of Ringer lactate (RL). The animals were then resuscitated with 3 times the volume of maximum bleedout with RL over 45 min followed by 2 times RL along with ATP-MgCl2 (50 mumol/kg body wt) over 95 min. Hepatocytes were isolated at 4, 17, and 27 h after resuscitation. P2-purinoceptor binding characteristics were determined by using [alpha-35S]ATP. Scatchard analysis revealed high-affinity and low-affinity receptor components in the hepatocytes isolated from sham-operated or hemorrhaged animals with or without ATP-MgCl2 infusion. ATP-MgCl2 ameliorated and subsequently restored the decreased maximum binding capacity (Bmax) of the high-affinity receptor component and significantly improved Bmax of the low-affinity receptor component. ATP-MgCl2 administration also produced a progressive enhancement in the affinity of the low-affinity receptor component. Thus the beneficial effects of ATP-MgCl2 observed after trauma-hemorrhage and resuscitation may be, in part, due to the restoration of P2-purinoceptor binding capacity and the enhancement of the receptor affinity.

Differential effects of ATP-MgCl2 on portal and hepatic arterial blood flow after hemorrhage and resuscitation.

Although ATP-MgCl2 administration after hemorrhage and resuscitation restores the decreased hepatic blood flow, it is not known whether this is due to the increase in portal blood flow or hepatic arterial blood flow. To study this, rats underwent a midline laparotomy (i.e., trauma induced) and were bled to and maintained at a mean arterial pressure of 40 mmHg until 40% of maximal shed blood volume was returned in the form of Ringer lactate (RL). The animals were resuscitated with four times the volume of the shed blood with RL, during and after which ATP-MgCl2 (50 mumol/kg body wt) or an equal volume of normal saline was infused intravenously over 95 min. Cardiac output and organ blood flow were determined by 85Sr-labeled microspheres at 90 min after the completion of resuscitation. The results indicate that portal blood flow and total hepatic blood flow decreased significantly after hemorrhage and resuscitation. ATP-MgCl2 treatment, however, restored these parameters to sham values. In contrast, hepatic arterial blood flow did not change significantly after either hemorrhage and resuscitation or ATP-MgCl2 infusion. Moreover, the depressed cardiac output was normalized and coronary blood flow was higher than shams after ATP-MgCl2 treatment. Unlike small intestinal blood flow, blood flows to the stomach, spleen, pancreas, mesentery, and cecum were not markedly affected with ATP-MgCl2 infusion. Thus the restoration of hepatic blood flow with ATP-MgCl2 treatment under such conditions is due to the increased portal blood flow, i.e., solely due to the increased small intestinal blood flow.

Use of ATP following Shock and Ischemiaa

The available information indicates that shock and ischemia are associated with such phenomena as diminished microcirculatory blood flow and diminished metabolic (including ATP levels) and cellular capabilities, and that these phenomena are associated with altered cellular functions. Infusion of ATP-MgCl2 as an adjunct following shock or ischemia significantly improves microcirculatory blood flow, tissue and mitochondrial magnesium levels, tissue ATP levels, cellular functions, and overall survival of animals. Administration of ATP or MgCl2 alone after such conditions was ineffective in improving cellular functions or the survival of animals. Thus, it could be concluded that ATP together with MgCl2 is required for an effective treatment. ATP-MgCl2 can be administered safely in normal volunteers as well as in patients following various adverse circulatory conditions. Administration of this agent in humans produces positive inotropic, negative chronotropic, and peripheral vasodilatory actions, which clearly suggests the potential use of this agent in patients with low-flow conditions or organ ischemia. Clinical trials of ATP-MgCl2 treatment in patients with various adverse circulatory conditions are underway at several institutions in this country as well as in Japan.

The effect of adenosine triphosphate on the functional status of the ductus arteriosus

We investigated whether a low-dose infusion of ATP-MgCl2 could affect the functional status of the ductus arteriosus during hypoxia-induced pulmonary vasoconstriction. Three-day-old piglets were made hypoxic by ventilation with a mixture containing 10% oxygen, 4% CO2, and balance nitrogen. Serial infusions of ATP-MgCl2 at 0.1, 0.5, and 1.0 mg/kg/min were compared with preinfusion hypoxia baselines. The functional status of the ductus arteriosus was determined by change in transit time of a bolus of iced saline between thermistor probes in the pulmonary artery and aorta. The method was validated using a Blalock-Taussing shunt (subclavian to pulmonary artery) in 3-week-old piglets instrumented in a similar manner. In these three-day-old piglets, hypoxia alone produced a significant elevation in pulmonary artery pressure and reduction in PO2. All dose rates of ATP-MgCl2 produced a significant decrease in mean pulmonary artery pressure. Systemic pressure was significantly decreased only during the 1.0-mg/kg/min infusion. Transit times of a bolus of iced saline during the validation were definitive for characterizing a situation of "shunt open" or "shunt closed." Infusion of ATP-MgCl2 produced no change in the status of the ductus arteriosus in 45 (94%) of the determinations. In only three cases was the effect of ATP-MgCl2 sufficient to result in a functional change in the status of the ductus arteriosus. Pre- and postductal pulmonary artery PO2 were not altered during ATP-MgCl2 infusion, thus corroborating the transit time determinations. From these results, we conclude that an infusion of ATP-MgCl2 does not alter the functional status of the ductus arteriosus.

Adenosine triphosphate: A potential therapy for hypoxic pulmonary hypertension

In this study we investigated whether a low-dose infusion of ATP-MgCl2 could ameliorate the pulmonary hypertension resulting from hypoxic pulmonary vasoconstriction. Three-week-old piglets were anesthetized, intubated, ventilated with room air, and cannulated for the measurement of pulmonary and systemic arterial pressure and pulmonary artery flow (cardiac output). The ventilator inflow was then changed to a mixture containing 10% oxygen, 4% CO2, and balance nitrogen. Serial infusions of ATP-MgCl2 at 0.1, 0.5 and 1.0 mg/kg/min were compared to preinfusion hypoxia baselines. Hypoxia alone produced a significant elevation in pulmonary artery pressure. Although all dose rates of ATP-MgCl2 produced a significant decrease (30%) in mean pulmonary artery pressure, we observed a maximum decrease in MPAP at the lowest rate of ATP infusion. Pulmonary artery flow rose slightly during ATP infusion; therefore, it was the change in pulmonary vascular resistance that accounted for the decrease in pulmonary artery pressure. In contrast, the systemic pressure was significantly decreased only during the 1.0 mg/kg/min infusion. The predominant pulmonary effects are a result of the virtual clearance of ATP-MgCl2 in a single pass through the circulation. Adenosine in the presence or absence of MgCl2 produced only a 10% reduction in mean pulmonary artery pressure, and MgCl2 had no effect when infused alone. From these results, we conclude that a low-dose infusion of ATP-MgCl2 could ameliorate the vasoconstriction associated with hypoxic pulmonary hypertension without significant deleterious systemic side effects.

Postischemic hemodynamics and recovery of renal adenosine triphosphate.

Renal vasoconstriction is an important pathophysiological component of an ischemic acute renal injury. The postischemic infusion of ATP-MgCl2 enhances recovery of glomerular and tubular function, accelerates regeneration of sublethally injured tubular cells, and augments resynthesis of cellular nucleotides. Since both ATP and MgCl2 are vasoactive compounds, postischemic enhancement of renal blood flow (RBF) by a pharmacological agent, dopamine, was examined to study the possible contribution of vasodilation. At 2 h, the infusion of dopamine resulted in RBF (1.70 +/- 0.09 ml X min-1 X 100 g body wt-1 X kidney-1) and inulin clearance (CIn, 400 +/- 44 microliter X min-1 X 100 g body wt-1) similar to rats treated with ATP-MgCl2 (1.73 +/- 0.27 RBF, 404 +/- 38 CIn) and significantly (P less than 0.01) greater than saline-treated rats (0.80 +/- 0.04 RBF, 78 +/- 19 CIn; P less than 0.01). However, by 24 h CIn in dopamine animals had not continued to improve (460 +/- 25 microliter X min-1 X 100 g body wt-1) and was similar to normal saline rats (388 +/- 40). In contrast, CIn in ATP-MgCl2 animals showed sustained recovery (676 +/- 28 microliter X min-1 X 100 g body wt-1, P less than 0.01). These differences resulted from improved integrity of tubular epithelium as reflected by decreased cell swelling and necrosis. Moreover, the recovery of renal ATP levels, as assessed by 31P nuclear magnetic resonance, in animals given saline (63 +/- 3%) or dopamine (66 +/- 5%) was slow and incomplete by 120 min after ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)

ATP-MgCl2 produces sustained improvement in hepatic mitochondrial function and blood flow after hepatic ischemia.

Recent studies have shown that infusion of ATP-MgCl2 following hepatic ischemia significantly improved mitochondrial function and hepatic blood flow 1 hr after treatment. To determine if the improvement in the above parameters by ATP-MgCl2 is short-lived or whether it persists for prolonged periods of time after treatment, hepatic ischemia in rats was produced for 90 min followed by reperfusion. The rats then received iv 0.5 ml of saline or ATP-MgCl2 (12.5 mumole each). Twenty-four hours after reflow, hepatic blood flow was measured by H2 polarography following which the animals were sacrificed and hepatic mitochondria isolated. The results indicated that 24 hr after reflow, mitochondrial state 3 respiration, respiratory control ratio, adenine nucleotide translocase activity, ATP synthetic activity, and hepatic blood flow were depressed by approximately 50% in animals which were treated with saline after hepatic ischemia. In addition, there was a fourfold increase in mitochondrial free fatty acid levels of such animals. Animals which were treated with ATP-MgCl2 following hepatic ischemia showed significantly improved mitochondrial function (used as an index of cellular recovery) and hepatic blood flow. These results in conjunction with previous results suggest that infused ATP-MgCl2 improves mitochondrial function and blood flow and that these effects persist even 24 hr after administration of ATP-MgCl2. Thus, infusion of ATP-MgCl2 following severe ischemia produces sustained improvement in cellular function.

Improved mitochondrial function following ischemia and reflow by ATP-MgCl2.

To determine whether infused ATP-MgCl2 affects mitochondrial adenine nucleotide translocase (ANT) activity, free fatty acids (FFAs), and Ca2+ levels, total hepatic ischemia in rats was produced for 90 min after which blood flow was allowed to return to the liver. Immediately on reflow, the animals received intravenously 0.5 ml of either saline, ATP-MgCl2 (12.5 mumol), or dopamine (6 mg/kg). Three hours after ischemia and reflow, hepatic mitochondrial FFAs and Ca2+ levels increased; however, ATP-MgCl2 infusion significantly lowered FFAs and restored Ca2+ levels. The depressed mitochondrial ANT activity was somewhat improved but not restored by circulatory support with dopamine; however, ATP-MgCl2 infusion following ischemia restored that activity. Thus the present results suggest that the improved organ function that occurs with ATP-MgCl2 infusion following ischemia may be mediated through an improvement in ischemia-induced mitochondrial function.

POSTISCHEMIC ATP-MGCL2 PROVIDES PRECURSORS FOR THE RESYNTHESIS OF CELLULAR ATP

Accelerated recovery of renal ATP levels have been documented in rats given a postischemic infusion of ATP-MgCl2. This observation could be related to a direct entry of ATP as a source of metabolic energy or to augmentation of the resynthesis of cellular ATP. To distinguish between these possibilities, rats were infused with either ATP-MgCl2 (25 μmoles), AMP-MgCl2 (25 μmoles) or normal saline (NS) after 45 min of renal ischemia. Renal cortical ATP levels were determined continuously in vivo, prior to, during and for 120 min after the ischemic injury using 31p NMR spectroscopy (TMR-32; 32.5 MHz for 31p). During the ischemia, cellular ATP levels fell rapidly and remained <10% of control values in all rats. ATP levels returned to 50% of control values within 10 min after the ischemic insult in all animals. In rats given NS, renal cortical levels of ATP recovered to only 65±2% at 2 hrs indicating a very slow and incomplete regeneration of cellular nucleotides. In contrast, the animals infused with ATP-MgCl2 (81±3%) or AMP-MgCl2 (83±4%) had significantly better (P<0.01) recovery of cellular ATP. Since ATP-MgCl2 and AMP-MgCl2 produced a similar result, it would appear that the infused ATP was not necessarily a direct source of cellular energy. Moreover, these findings would suggest that the postischemic infusion of ATP-MgCl2 provides precursors for the repletion of the tissue nucleotide pool and resynthesis of cellular ATP.

HEMODYNAMIC EFFECT OF POST-ISCHEMIC ATP-MGCL2

The postischemic infusion of ATP-MgCl2 is known to enhance recovery from acute renal failure. Since both ATP and MgCl2 are vasoactive compounds and increase renal blood flow (RBF), the hemodynamic effects of this complex were determined by treating animals with either dopamine (15 μg/kg), ATP-MgCl2 (25 μmoles) or normal saline (NS) after 45 min of renal ischemia. Inulin clearance (Cin) and renal blood flow (electromagnetic flow probe) were determined at 2 hrs and Cin and recovery of microinjected inulin (InR%) were evaluated 24 hrs after the injury.At 2 hrs the infusion of dopamine resulted in a level of RBF (1.70±0.09 ml/min/100gBW/kidney) and Cin (400±44 μl/min/100gBW) that was similar to that in the ATP-MgCl2 rats (1.73±0.27 RBF, 404±38 Cin and significantly (P<0.01) greater than NS rats (0.80±0.04 RBF, 78±19 Cin; P<0.01). However, by 24 hrs the Cin in dopamine animals had not continued to improve (460±25) and was similar to that in NS animals (388±40). In contrast, Cin in ATP-MgCl2 animals showed sustained and accelerated recovery (676±28; P<0.01). These differences resulted from improved integrity of the tubular epithelium as reflected by diminished backleak: InR 92±3% ATP-MgCl2; 45±5% dopamine; P<0.01).This study demonstrates that the initial hemodynamic effect of ATP-MgCl2 produces some improvement in Cin but the sustained salutary effect of this compound is related to the repair of sublethally injured tubular cells and restoration of cellular metabolism, which we have previously documented.

Enhanced recovery of renal ATP with postischemic infusion of ATP-MgCl2 determined by 31P-NMR.

The postischemic infusion of ATP-MgCl2 will enhance the recovery of both glomerular and tubular function. To assess the effect of ATP-MgCl2 on tissue nucleotides, 31P nuclear magnetic resonance (31P-NMR) spectra were obtained continuously in vivo from the left kidney of rats that had been subjected to 45 min of renal ischemia and then infused with either normal saline or ATP-MgCl2. 31P-NMR spectra with distinct peaks for alpha-, beta-, and gamma-phosphate of ATP, sugar phosphate, and inorganic phosphate were collected every 7 min before, during, and after renal artery occlusion. During ischemia, the ATP beta-peak (the only peak unique to ATP) fell rapidly to 10% of control values in both groups of animals. By 120 min after the ischemic insult, the animals treated with ATP-MgCl2 had recovery of renal ATP to 89 +/- 2.6%, which is significantly greater (P less than 0.001) than 65.2 +/- 1.8% found in rats given normal saline. These data indicate that 1) 31P-NMR can be used to assess renal ATP levels continuously in vivo; 2) during renal ischemia ATP levels fall quickly to less than 10% of control values; 3) tissue ATP returns relatively slowly to control values in rats given normal saline, whereas postischemic treatment with ATP-MgCl2 results in an accelerated recovery of tissue ATP levels. These findings provide a biochemical correlate to the improvement in renal function previously described.

Studies on the mechanism of beneficial effects of ATP-MgCl2 following hepatic ischemia.

Infusion of ATP-MgCl2 following hepatic ischemia significantly improves the survival of animals. To determine the subcellular effects of infused ATP-MgCl2 and whether such effects are mediated through vasodilatation, global hepatic ischemia in rats was produced for 90 min followed by reperfusion. The rats then received iv 0.5 ml of saline, dopamine, papaverine, or ATP-MgCl2. At various intervals following reflow, hepatic mitochondria were isolated. ADP-to-O ratio and respiratory control ratio (RCR) were significantly lower 1 h following reflow, and there was a further decrease in these parameters 3 h after reflow in mitochondria from saline-treated rats. Dopamine and papaverine treatment did not improve RCR, however, ATP-MgCl2 treatment resulted in a progressive and significantly higher ADP/O and RCR following reflow. Hepatic ATP levels in saline, dopamine, and papaverine-treated rats were found to be 50% lower 3 h following reflow, however, treatment with ATP-MgCl2 resulted in significantly higher ATP levels and energy charge. Hepatic blood flow was markedly depressed 1 h following reflow in the saline-treated rats but was significantly higher in the ATP-MgCl2 group. Three hours following reflow, hepatic blood flow decreased further in the saline-treated rats, whereas in the ATP-MgCl2-treated rats there was a progressive increase in flow. Dopamine treatment resulted in an initial restoration in flow, however, this effect was not sustained. Hepatic ultrastructure deteriorated progressively following reflow in the saline-treated rats, however, it was normal in the ATP-MgCl2-treated rats 1 h as well as 20 h following reflow. These results lead us to conclude that infused ATP-MgCl2 improves mitochondrial and cellular functions either directly or by way of long-term improvement in microcirculation but not through vasodilatation.

Accelerated recovery of single nephron function by the postischemic infusion of ATP-MgCl2

This study was designed to investigate the effects of ATP-MgCl2 when infused immediately 8 or 24 hr after 45 min of bilateral renal artery ischemia and to determine if an initial improvement in clearance of inulin (CIn) would be sustained throughout the course of recovery. In addition, the influence of ATP-MgCl2 on the pattern of recovery of whole kidney and single nephron function was assessed by determining the impact of this agent on proximal tubular pressure and transepithelial backleak. The postischemic administration of ATP-MgCl2 resulted in significantly enhanced recovery of CIn irrespective of the time of the infusion after the initial insult. This beneficial effect was sustained in that the ATP-MgCl2-treated rats had significantly better CIn 1, 3 and 7 days after the injury when compared to normal saline-treated animals. Moreover, single nephron inulin clearance (SNCIn) was better preserved than whole kidney CIn in both groups of animals and in the ATP-MgCl2-treated animals SNCIn was similar to control values even 1 day after the injury. The enhanced recovery of single nephron function in the ATP-MgCl2-treated animals resulted from reduced proximal tubular pressure and diminished backleak of tubular fluid. Animals given ATP-MgCl2 had better preservation of cellular morphology. Horseradish peroxidase was excluded from most epithelial cells and the interstitium in a manner similar to that seen in control animals while saline-treated rats demonstrated backleak of this tracer compound. Based on these studies, it appears that the beneficial effect of ATP-MgCl2 occurs because of the preservation of sublethally injured cells by augmentation of the process of recovery.