High-energy Phosphate Stores Research Articles

Protection by verapamil of globally ischemic rat hearts: Energy preservation, a partial explanation

The relationship between energy preservation and the recovery of heart function was studied in globally ischemic hearts which were treated with verapamil. Isolated working rat hearts reperfused after 27 min of ischemia recovered 17.9 +/- 5.11% of pre-ischemic contractile function and had markedly reduced tissue ATP, total adenine nucleotide, and creatine phosphate levels. The ATP/ADP ratio was also decreased in these hearts. When verapamil (2 X 10(-6) M) was present before and during ischemia, but not during reperfusion, the recovery of cardiac function following reperfusion was improved (82.4 +/- 12.1%). When hearts were treated with 0.0, 7.5 X 10(-8) M, 5 X 10(-7) M, or 2 X 10(-6) M verapamil, the recovery of cardiac function was proportional to the concentration of verapamil present and showed a linear relationship with the depression of cardiac function prior to ischemia. The ATP, total adenine nucleotide and creatine phosphate levels were significantly higher in those hearts which were treated with verapamil, but the increase was not proportional to the recovery of cardiac function. It is possible that a critical pool of ATP may correlate with the recovery of verapamil treated hearts, but a large degree of mechanical recovery occurred with significant loss of high energy phosphate stores. Thus, while high energy compounds were preserved, there was not a good correlation between recovery of cardiac function and the preservation of total tissue energy reserves. A portion of the protection afforded by verapamil to globally ischemic hearts may be due to energy preservation, but additional mechanisms may also be involved in the enhanced recovery of contractile function.

Protection of the hypertrophied pig myocardium: A comparison of crystalloid, blood, and Fluosol-DA cardioplegia during prolonged aortic clamping

The myocardial protective effects of crystalloid, blood, and Fluosol-DA-20% cardioplegia were compared by subjecting hypertrophied pig hearts to 3 hours of hypothermic (10 degrees to 15 degrees C), hyperkalemic (20 mEq/L) cardioplegic arrest and 1 hour of normothermic reperfusion. Left ventricular hypertrophy was created in piglets by banding of the ascending aorta, with increase of the left ventricular weight-body weight ratio from 3.01 +/- 0.2 gm/kg (control adult pigs) to 5.50 +/- 0.2 gm/kg (p less than 0.001). An in vivo isolated heart preparation was established in 39 grown banded pigs, which were divided into three groups to receive aerated crystalloid (oxygen tension 141 +/- 4 mm Hg), oxygenated blood (oxygen tension 584 +/- 41 mm Hg), or oxygenated Fluosol-DA-20% (oxygen tension 586 +/- 25 mm Hg) cardioplegic solutions. The use of crystalloid cardioplegia was associated with the following: a low cardioplegia-coronary sinus oxygen content difference (0.6 +/- 0.1 vol%), progressive depletion of myocardial creatine phosphate and adenosine triphosphate during cardioplegic arrest, minimal recovery of developed pressure (16% +/- 8%) and its first derivative (12% +/- 7%), and marked structural deterioration during reperfusion. Enhanced oxygen uptake during cardioplegic infusions was observed with blood cardioplegia (5.0 +/- 0.3 vol%), along with excellent preservation of high-energy phosphate stores and significantly improved postischemic left ventricular performance (developed pressure, 54% +/- 4%; first derivative of left ventricular pressure, 50% +/- 5%). The best results were obtained with Fluosol-DA-20% cardioplegia. This produced a high cardioplegia-coronary sinus oxygen content difference (5.8 +/- 0.1 vol%), effectively sustained myocardial creatine phosphate and adenosine triphosphate concentrations during the extended interval of arrest, and ensured the greatest hemodynamic recovery (developed pressure, 81% +/- 6%, first derivative of left ventricular pressure, 80% +/- 10%) and the least adverse morphologic alterations during reperfusion. It is concluded that oxygenated Fluosol-DA-20% cardioplegia is superior to oxygenated blood and especially aerated crystalloid cardioplegia in protecting the hypertrophied pig myocardium during prolonged aortic clamping.

Uncoupling between beta-adrenoceptors and adenylate cyclase in dog ischemic myocardium.

We evaluated the effects of ischemic injury on the myocardial adenylate cyclase system, 5 h after ligation of the left anterior descending coronary in 5 anesthetized dogs. Crude cardiac membrane preparations were isolated from control and ischemic areas of ventricular myocardium and tested for: 1. L-(125I)iodocyanopindolol binding, in the absence and presence of +/- -isoprenaline and GTP, and 2. adenylate cyclase activity. The density of beta-adrenoceptors increased by 35% in membranes from ischemic areas while the proportion of receptors in a high affinity state for +/- -isoprenaline decreased from 43% to 20%. Adenylate cyclase activities in the basal state and under stimulation with NaF, forskolin, Gpp(NH)p, +/- -isoprenaline and VIP were all markedly and similarly reduced, being only about 30% of comparable activities in membranes from control areas. The +/- -isoprenaline subsensitivity of cardiac adenylate cyclase can, thus, be attributed to a defective enzymatic system and not to a reduction in the number of beta-adrenoceptors implying that the internal components of the system were more sensitive to acute ischemia than the outward oriented hormone receptors. It is tempting to ascribe this uncoupling to a functional depletion in the guanine nucleotide-binding regulatory protein Ns that might reflect a loss of high energy phosphate stores including GTP.

Effects of Delay in Administration of Potassium Cardioplegia to the Isolated Rat Heart

Ischemic injury to the heart in the period between aortic cross-clamping and administration of cardioplegic solution was evaluated in the normothermic rat heart model. After isolation and control perfusion with oxygenated Krebs-Henseleit bicarbonate buffer, the hearts were given lactated Ringer's cardioplegic solution (30 mEq of K + per liter) for 2 minutes at three different intervals following aortic clamping: no delay, 2-minute delay, and 5-minute delay. Thereafter, the hearts were left unper-fused and the time to initiation of ischemic contracture was recorded. Adenosine triphosphate (ATP) and creatine phosphate levels were measured in all groups prior to and at the conclusion of cardioplegia administration. A 2-minute delay in the administration of cardioplegic solution resulted in significantly lower ( p < 0.001) ATP levels that were restored after 2 minutes of cardioplegia administration. Contracture times were not significantly altered. A 5-minute delay resulted in significantly shorter ( p < 0.001) contracture times and significantly lower ( p < 0.001) ATP levels that were not restored to preischemic levels by 2 minutes of cardioplegia administration. The fate of the myocardium may be insensitive to events that occur during the earliest moments of ischemia provided that rapid administration of oxygenated potassium cardioplegia follows the ischemic period and restores preischemic high-energy phosphate stores. However, there is a critical ischemic time during the initial interval before cardioplegia that is associated with an impaired ability of the myocardium to tolerate subsequent ischemia.

Effect of prostacyclin infusion during low-flow ischaemia in the isolated perfused rat heart.

Although prostacyclin (PGI2) has been shown to exert a protective effect on ischaemic hearts its precise mode of action remains obscure. Possible explanations include protection of the high energy phosphate stores (ATP and CP), maintenance of homeostasis with respect to Ca2+, and an antiaggregatory effect. The following experiments were undertaken to investigate these possibilities, using isolated, spontaneously beating rat hearts perfused with Krebs-Henseleit solution. Ischaemia was induced at 37 degrees C for 30 min by reducing the flow rate from 10.0 to 0.1 ml/min, and was followed by reperfusion. PGI2 was given as a constant infusion (20 ng/ml). The hearts were frozen and assayed for ATP and CP, or digested in HNO3 and assayed for Ca2+. Peak developed tension was recorded throughout. The results show that PGI2 slowed the rate of decline of developed tension during low flow perfusion, and hastened the recovery of contractions on reperfusion. These effects could not be accounted for in terms of an improved supply of ATP or CP, or an altered tissue Ca2+. The protective effect of PGI2 on isolated, buffer-perfused hearts may be a reflection of a generalized, but undefined, mechanism of cell preservation which has also been observed in other systems.

Global ischemia in the immature canine ventricle: Enhanced protective effect of verapamil and potassium

The efficacy of the addition of verapamil to a cardioplegic solution was evaluated in immature canine hearts subjected to normothermic global ischemia. Two groups of mongrel puppies less than 10 weeks old were subjected to 30 minutes of global myocardial ischemia while on cardiopulmonary bypass. One group (Group K) was arrested with cardioplegic solution containing 20 mEq/L of KCl; the other group (Group K + V) was arrested with the same solution containing 0.2 mg/kg of verapamil. Ultrasonic crystals were placed for measurement of left ventricular dimensions, and micromanometers measured left ventricular pressures. Functional measurements included left ventricular strain, first derivative of left ventricular pressure (dP/dt), and the end-systolic pressure/volume ratio (Emax). Metabolic recovery was assessed by measuring myocardial adenosine triphosphate (ATP) content. Ninety minutes following ischemia, Group K + V exhibited greater minor axis strain at a left ventricular end-diastolic pressure of 15 and 20 mm Hg (p less than 0.05), greater dP/dt (p less than 0.05 to 0.001), and greater Emax (p less than 0.05) than Group K. ATP content in Group K + V was greater at 60 minutes (Group K + V: 12.74 +/- 1.60 mumol/gm; Group K: 8.39 +/- 1.30, p less than 0.05) and 90 minutes (Group K + V: 10.34 +/- 0.46; Group K: 7.55 +/- 1.42, p less than 0.05) after ischemia. The addition of verapamil to a cardioplegic solution containing potassium enhances the recovery of function and high-energy phosphate stores in the immature myocardium following normothermic global ischemia.

Evaluation of cardiac anoxia and ischemia models in the rat using calcium antagonists

The effects of severe global ischemia on cardiac high energy phosphate (HEP) stores were investigated in an in vitro rat model. The heart was removed from the rat in this model, sealed in a plastic bag and incubated for varying times and temperatures (20–45°C). The rat, in the in vivo anoxic model, was subjected to cervical dislocation which resulted in respiratory arrest. In both models the hearts were removed and analyzed for HEP at appropriate times following the onset of anoxia or ischemia. Verapamil and nifedipine, administered intravenously 10 minutes before the start of the experiments, preserved HEP stores in both models. The degree of protection provided by the Ca +2 blockers was related to both the dose of drug and the duration of the ischemia/anoxia. Verapamil was more active than nifedipine in both models.

Role of Na+-Ca2+ exchange in the development of cardiac abnormalities due to calcium paradox.

Reperfusion of rat heart with Ca2+-containing medium for 1 to 10 min after a 5 min perfusion with Ca2+-free medium resulted in a generalized disruption of myocardial ultrastructure including swelling of sarcoplasmic reticulum and mitochondria, depletion of creatine phosphate and adenosine triphosphate stores, reduction of the microsomal but augmentation of the mitochondrial Ca2+ uptake activities and elevation of the cardiac Na+ as well as Ca2+ contents. These hearts developed contracture and were unable to generate contractile force. Lowering the concentration of Na+ from 145 to 35 mmol l-1 in the medium during Ca2+-free perfusion was observed to markedly reduce or prevent the reperfusion induced changes in myocardium. On the other hand, lowering the concentration of Na+ in the medium during the reperfusion phase following a 5 min perfusion with Ca2+-free medium enhanced the rate of depletion of the high energy phosphate stores and the rate of elevation of myocardial Ca2+ contents but markedly depressed the rise in Na+ contents. These results suggest that Ca2+-paradoxical changes in myocardium occur as a consequence of the intracellular Ca2+ overload in which Ca2+ entry through Na+-Ca2+ exchange mechanism at the cell membrane may be an important contributory factor.

Cardiac and renal responses to cross-clamping of the descending thoracic aorta

The present study was performed to document the relative efficacy of commonly applied techniques used adjunctively during 1 hour of descending thoracic aortic cross-clamping. Renal and cardiac responses were determined by standard laboratory methods. There were four experimental groups: (1) heparin-bonded shunt; (2) partial femoral-femoral bypass; (3) sodium nitroprusside; (4) control. Each of the experimental groups showed abnormal hemodynamic responses during cross-clamping. Elevations in left ventricular end-diastolic pressure (LVEDP) and systolic blood pressure were common events during clamping, and cardiac output often decreased. Nevertheless, left ventricular performance curves after cross-clamping showed similar increases in left ventricular stroke work (LVSW) with increasing preload. In addition, left ventricular biopsy specimens showed preservation of myocardial high-energy phosphate stores and essentially normal ultrastructural integrity. Radioactive microspheres generally showed increased myocardial blood flow during and after cross-clamping, but no evidence of preferential subendocardial ischemia. Examination of renal function showed a marked decrease in urine output, glomerular filtration rate, and renal plasma flow during cross-clamping. Following the release of the cross-clamp, renal function returned to 50% to 85% of baseline status. Since we could find no major advantage of any of the techniques employed under the present experimental conditions, we suggest that all of the techniques should be part of the surgical armamentarium and the particular preoperative and/or intraoperative findings in a specific case should determine which technique is most appropriate for a given patient.

Abnormal changes in high energy phosphate stores during inotropic stimulation of the failing myocardium: H. Pouleur, G. Maréchal, M.F. Rousseau, A.A. Charlier. Depts of Physiology and Cardiology, University of Louvain, Brussels, Belgium

Abnormal changes in high energy phosphate stores during inotropic stimulation of the failing myocardium: H. Pouleur, G. Maréchal, M.F. Rousseau, A.A. Charlier. Depts of Physiology and Cardiology, University of Louvain, Brussels, Belgium

The Optimal Temperature for Preservation of the Myocardium during Global Ischemia

To determine the myocardial temperature that provides maximal preservation of the heart during global ischemic arrest, five groups of dogs were studied (6 per group). In all animals, the aorta was cross-clamped for 120 minutes. Serial biopsies were done for determination of adenosine triphosphate and creatine phosphate, and study by electron microscopy. Starling curves were derived prior to cardiopulmonary bypass and 60 minutes after bypass. Mitochondrial changes were graded on a scale of 0 to 4. In the control group (Group 1), the aorta was clamped when the rectal temperature reached 25°C (myocardial temperature, 18° to 22°C). In Groups 2, 3, 4, and 5, myocardial temperature was maintained at 6°C, 10°C, 14°C, and 18°C (all ± 2°C), respectively, by the use of systemic and topical hypothermia and repeated injections of cold cardioplegia solution into the aortic root. All groups showed a depression of left ventricular stroke work index, particularly Group 1 (no survivors), Group 2, and Group 3. The high-energy phosphate stores were well preserved in all groups except Group 1. The mitochondrial ultrastructure showed significant changes in all groups, especially Groups 1 and 5. These data indicate that satisfactory preservation of mitochondrial ultrastructure and high-energy phosphates was achieved at myocardial temperatures lower than 18°C. Extreme hypothermia (Groups 2 and 3) was associated with significant reduction in ventricular function under the experimental conditions employed.

Myocardial metabolism and regional myocardial blood flow in the canine left ventricle following twenty minutes of circumflex artery occlusion and reperfusion

The recovery of high energy phosphate stores (ATP plus phosphocreatine) was examined following various periods of reperfusion after 20 min circumflex artery occlusion in the open-chest dog. Transmural tissue samples were obtained from the posterior wall of the left ventricle of control dogs, after 20 min occlusion and after 1, 5, 10, 15 and 20 min reperfusion. Significant reductions in high energy phosphate stores were observed in the subepicardium (41.6% of control) and subendocardium (31.3% of control) after occlusion. Upon reperfusion, recovery was rapid and exceeded control by 65.4% (91.0 v. 55.0 μm/g dry wt) in the subendocardium, but only by 2.6% (72.2 v. 70.4, μmg/g dry wt) in the subepicardium and was due mainly to recovery of phosphocreatine. Regional myocardial blood flow was studied in a separate, but identical, series of experiments. During occlusion, posterior wall blood flow was reduced by 54% (0.85 ± 0.04 to 0.37 ± 0.04, ml/g/min) in the subepicardium and by 94.7% (1.13 ± 0.05 to 0.06 ± 0.005, ml/g/min) in the subendocardium. Reperfusion produced a rapid recovery including overshoot of blood flow compared to control blood flow. Peak blood flow occurred one minute after release of the occlusion becoming 3.34 ± 0.16 ml/g/min in the subepicardium and 2.39 ± 0.13 ml/g/min in the subendocardium. Blood flow in both levels returned to control flow after 15 min reperfusion. These results indicate that metabolic recovery of high energy phosphate stores occurred within 5 min of restoration of blood flow in this model.

Energy production and utilization in contractile failure due to intracellular calcium overload.

Intracellular calcium overload was produced by perfusing the Ca2+- deprived rat hearts for 5 or 10 min with normal medium containing 1.25 mM Ca2+ for 10 min and changes in the myofibrillar and membrane ATPase, sarcolemmal adenylate cyclase, mitochondrial oxidative phosphorylation and high energy phosphate stores in failing hearts were examined. Myocardial creatine phosphate and ATP were decreased by the intracellular calcium overload whereas the myofibrillar, mitochondrial and microsomal ATPase activities were not altered. The intracellular calcium overload markedly depressed the mitochondrial oxidative phosphorylation as well as sarcolemmal Ca2+ ATPase, Mg2+ ATPase, Na+ - K+ ATPase and adenylate cyclase. These results suggest that abnormalities in the process of energy production rather than energy utilization may primarily account for the depressed energy state of hearts failing due to an intracellular calcium overload.

Metabolic and mechanical effects using L- and D-carnitine in working swine hearts.

The purpose of the present studies was to contrast the differences in mechanical and metabolic functions between treatments of L- and D-carnitine as measured in intact, regionally ischemic swine hearts. Coronary flows were decreased in the anterior descending circulation (-53% delta) after an equilibration period of 30 min during which hearts in both treatment groups were supplemented with trace-labeled [U14-C]palmitate. Nine hearts were selectively treated with L-carnitine (avg serum concentration 804 nmol/ml) and were compared with eight hearts treated with D-carnitine (same dosage schedule). No differences in fatty acid metabolism or regional shortening were observed between treatment groups in the heart muscle rendered moderate-to-severely ischemic. L-Carnitine did effect a significant reduction in fatty acid uptake and labeled CO2 production as compared with D-carnitine in aerobic tissue. This resulted in a secondary improvement in global mechanical efficiency (expressed as a ratio of either left ventricular developed pressure or work/global oxygen consumption) in L-treated hearts. Higher levels of high-energy phosphate stores were also noted in both ischemic and aerobic tissue of L-treated hearts. Thus differences in fatty acid metabolism occurred in working swine hearts based on the structural specificity of carnitine treatment. L-Carnitine favorably modified oxygen consumption and global mechanical efficiency.

Depressed high-energy phosphate content in hypertrophied ventricles of animal and man: the biologic basis for increased sensitivity to ischemic injury.

It is frequently stated that hypertrophied ventricles tolerate ischemia less well than nonhypertrophied ventricles. The authors' earlier studies in a rat supravalvular aortic stenosis model and canine valvular aortic stenosis model, both with concentric left ventricular hypertrophy, disclosed accelerated rates of ischemic contracture and diminished basal myocardial high energy phosphate stores. These studies have been extended to ten patients with severe left ventricular hypertrophy caused by valvular aortic stenosis and normal coronary arteries. ATP (endocardial and epicardial) from transmural left ventricular biopsies taken at operation before aorta cross-clamping, and frozen immediately in liquid nitrogen, were compared with similar biopsies from patients with nonhypertrophied myocardium supplied by normal coronary arteries. The subendocardial high energy phosphate levels in the nonhypertrophied myocardium was greater than high energy phosphate levels in the subepicardium of nonhypertrophied ventricles (ATP-micromoles/gram-protein, epi = 36.8 +/- 3.3, endo = 37.7 +/- 3.3) (p = NS). However, in the hypertrophied myocardium the subendocardium consistently showed significantly depressed high-energy phosphate levels when compared with subepicardial levels (ATP-hypertrophied myocardium, epi = 31.5 +/- 1.6, endo = 25.9 +/- 1.7) (p less than 0.05). This uniform depression of ATP stores, greatest in the subendocardium, in left ventricular hypertrophy suggests a common biologic mechanism for the enhanced sensitivity to ischemia. Of importance for patients may be the prior observation in rats that repletion of ATP( stores before ischemia eliminates the accelerated rate to ischemic contracture. Diminished subendocardial ATP stores appear to be an intrinsic property of severely hypertrophied myocardium and probably contribute to its enhanced sensitivity to ischemia.

Improved tolerance to ischemia in hypertrophied myocardium by preischemic enhancement of adenosine triphosphate

In prior studies from this laboratory to determine the mechanisms whereby hypertrophied myocardium is more sensitive to ischemic injury than normal myocardium, it was demonstrated that hypertrophied rat hearts have lower basal high-energy phosphate levels and develop ischemic contracture sooner than normal myocardium. The purposes of this study were (1) to determine if the decrease in myocardial adenosine triphosphate (ATP) was associated with the increased rate of ischemic contracture and (2) to determine if arrest and perfusion of hypertrophied myocardium prior to the ischemic interval would allow recovery of high-energy phosphate stores and improve tolerance to ischemia. ATP levels were measured in isolated normal and hypertrophied rat hearts during (1) control nonworking Langendorff perfusion, (2)2 minutes of potassium chloride-arrested perfusion (30 mEq/L), or (3) 15 minutes of potassium chloride-arrested perfusion (30 mEq/L). Both groups were then made globally ischemic (37 degrees C) and the time to ischemic contracture recorded. Hypertrophied hearts were produced by permanent banding of the ascending aorta and confirmed by left ventricular (mg) body weight (gm) ratios (normal, 1.95 wet, p less than 0.05). After 2 minutes of mechanical arrest the time to ischemic contracture was increased 75% +/- 10% in normal and 44% +/- 4% in hypertrophied hearts. After 15 minutes of mechanical arrest with perfusion, hypertrophied myocardium re-established normal ATP levels and increased its time to ischemic contracture by 130% +/- 7%. These studies suggest that during potassium chloride arrest, additional preischemic metabolic recovery is possible by hypertrophied myocardium and leads to increased tolerance to ischemia beyond that accomplished by cessation of mechanical activity alone. This effect is seen only to a minor degree in normal myocardium.

Effect of prostaglandin on cell membrane permeability and hepatic high-energy stores following hemorrhagic shock

Infusion of prostaglandin E 1 is known to exert a beneficial effect in hemorrhagic shock. It is also known that hemorrhagic shock lowers hepatic stores of high-energy phosphates and that restoration of hepatic ATP is associated with improved organ function and survival. The present study was undertaken to evaluate the effect of infusion of exogenous prostaglandin E 1 on (1) hepatic ATP levels and (2) restoration of hepatic ATP-dependent intracellular function. Rats were subjected to hemorrhagic shock, resuscitated, and then treated with either prostaglandin E 1 or a saline placebo. Ten minutes after the completion of treatment, hepatic ATP levels were significantly higher in prostaglandin-treated animals (1.37 ± 0.43 μmol/g) than in animals receiving the placebo (0.70 ± 0.11 μmol/g). Creatine phosphate levels were also higher in the prostaglandin-treated group (1.59 ± 0.16 μmol/g) than in the placebo-treated group (0.89 ± 0.14 μmol/g). Lactate production ratios, an index of ATP-dependent membrane function, were near the theoretical normal of 100% in unshocked, untreated animals (95 ± 10%). They were significantly reduced (57 ± 10%) in animals receiving only placebo, but were not significantly different from unshocked animals in those receiving prostaglandin E 1 following shock (91 ± 10%). It is concluded that prostaglandin infusion improves both hepatic high-energy phosphate levels and ATP-dependent intracellular function following hemorrhagic shock. This might be due to replenishing the purine base, selectively increasing hepatic blood flow, or both.

A protective effect of verapamil on the calcium paradox in the isolated perfused rat heart

Experiments were undertaken to examine whether and how verapamil, one of the well known slow-channel calcium-antagonists, protected cardiac muscles against the calcium paradox in isolated perfused rat hearts. Following a 5-min perfusion with calcium-free buffer at pressure of 80 cm H 2O (high flow) and 40 cm H 2O (low flow), severe and mild calcium paradoxical injuries were produced, respectively, by reperfusion with buffer containing 2.5 m m of calcium for 10 min at 80 cm H 2O. When verapamil (1 mg/l) was added to the perfusion medium during both the calcium depletion and repletion periods, a marked protective effect on the mild calcium paradox was observed, evidenced by a higher recovery in the contractility, an about 50% reduction in development of the contracture, and almost complete prevention in release of creatine kinase, an inhibition of tissue calcium accumulation, and much larger tissue stores of high energy phosphates; whereas no protective effect was observed on the severe calcium paradox. In the mild calcium paradox, administration of verapamil up to 2 min after the readmission of calcium was sufficient for protection against the calcium paradox. It was suggested that verapamil could substantially protect heart muscles from injuries associated with the calcium paradox probably due to an inhibition of sudden calcium influx into the cardiac cells in early calcium repletion period.

Studies on the significance of serum mitochondrial aspartate aminotransferase activity following ischemic cardiac arrest.

Aspartate aminotransferase (EC 2.6.1.1:AST) is known to have two isoenzymes, one associated with the cytoplasm (c-AST) and the other with the mitochondria (m-AST). We studied the relationships of m-AST activity in the coronary sinus blood to left ventricular function, coronary blood flow, water content and high-energy phosphate stores of the left ventricle following hypothermic ischemic cardiac arrest. Under cardiopulmonary bypass with hypothermia of 20 degrees C of myocardial temperature, 120 min of aortic occlusion was employed in 15 mongrel dogs. Left ventricular function (peak left ventricular pressure, left ventricular end-diastolic pressure, max dp/dt, cardiac index, left ventricular stroke work index), coronary blood flow, myocardial oxygen consumption, myocardial enzyme activity (m-AST, CK-MB), myocardial water content and high-energy phosphate stores (adenosine triphosphate, creatine phosphate) of the subendocardium of the left ventricle were measured. Data was obtained in the control state, and after 0, 30 and 60 min of reperfusion. Significant negative correlations were obtained between m-AST activity and peak left ventricular pressure (r = -0.81, p less than 0.001), max dp/dt (r = -0.83, p less than 0.001), cardiac product (r = -0.73, p less than 0.01), coronary blood flow (r = -0.59, p less than 0.05), adenosine triphosphate level (r = 0.72, p less than 0.01) and creatine phosphate level (r = -0.72, p less than 0.02) after 60 min of reperfusion. Significant positive correlations were obtained between m-AST activity and left ventricular end-diastolic pressure (r=0.75, p less than 0.01) and water content (r = 0.78, p less than 0.01) after 60 min of reperfusion. These results led to the assumption that serum m-AST activity in the coronary venous blood is a useful index to evaluate the degree of myocardial injury.

Correlation of pancreatic blood flow and high-energy phosphates during experimental pancreatitis.

A dog model was used to measure the hemodynamic changes occurring during acute pancreatitis induced by intraductal injection of fresh trypsin-bile-blood mixture. Pancreatic blood flow was measured with 15-micrometer radioactive microspheres. Measurements of pancreatic adenosine triphosphate (ATP) and creatine phosphate (CP) were made under normal conditions and during acute hemorrhagic pancreatitis. Basal ATP and CP concentrations were 5.82 +/- 0.25 and 5.30 +/- 0.31 mmol/g wet tissue, respectively. Hemorrhagic pancreatitis was characterized by a severe reduction in pancreatic blood flow, followed by a 45% fall of ATP and a 70% lowering of CP. These results suggest that inadequate pancreatic tissue perfusion during acute pancreatitis results in a marked depletion of high-energy phosphate stores. We suspect this energy depletion reflects the progression of the disease from edematous to hemorrhagic pancreatitis and causes irreversible damage of pancreatic tissue.