Previous hyperthermic treatment increases mitochondria oxidative enzyme activity and exercise capacity in rats

The study was designed to investigate the role of hyperthermia in the tolerance of exercise in rats and the possible mechanism was examined. The hyperthermic pretreatment was performed using an electric pad on the anesthesized rats 24 hours before exercise. Rats were exercised passively in a motor-controlled round treadmill in high temperature environment (36-37 degrees C) until exhaustion. The capacity of tolerance was calculated. Lymphocytes and gastrocnemius muscle were collected from both groups. The changes in muscular morphology, mitochondria oxidative enzyme activity and induction of Hsp72 were investigated. The results revealed that experimental rats were more tolerant to exercise at high temperature than the control group; the duration time were 89 +/- 17.8 min and 63.1 +/- 7.3 min, respectively. Hsp72 was induced markedly in the experimental group, both in muscle and lymphocytes, indicating a heat shock response. There was no significant change in morphology of the mitochondria, 24 hours after hyperthermic treatment, as shown by histopathological and electromicroscopic investigation. However, the activity of mitochondrial enzymes increased significantly in experimental group before exercise: 84.6 +/- 6.3 and 345 +/- 15.4 (nmole cytochrome c/min/mg total protein) respectively of NADH-cytochome c reductase and succinate-cytochome c reductase activity in experimental group compared to 58.9 +/- 4.7 and 269.0 +/- 24.0 in control group (p < 0.05, by student t-test). It is concluded that hyperthermic treatment enhances muscular mitochondrial oxidative enzyme activity in rats, and results in increasing tolerance to exercise at high temperature. The heat shock response, most probably the inducible Hsp72, is a crucial factor in this effect.     

Heat shock protein induction in rat hearts. A role for improved myocardial salvage after ischemia and reperfusion?

BACKGROUND. To test the hypothesis that the heat shock response is associated with improved myocardial salvage after myocardial ischemia and reperfusion, rats treated with prior whole-body hyperthermia and 24 hours of recovery (n = 26) or 20 minutes of ischemic pretreatment and 8 hours of recovery (n = 24) and control rats (n = 27, n = 24, for hyperthermic and ischemic pretreatment, respectively) were subjected to 35 minutes of left coronary artery (LCA) occlusion and 120 minutes of reperfusion. METHODS AND RESULTS. Although ventricular samples from rats subjected to either hyperthermia (n = 7) or ischemic pretreatment (n = 6) all showed induction of HSP72 (heat shock protein), Western blot analysis revealed significantly greater amounts of HSP72 in samples obtained from rats subjected to hyperthermia compared with those from rats subjected to ischemic pretreatment. Control rats (n = 7) showed no significant presence of myocardial HSP72. After 35 minutes of LCA occlusion and 2 hours of reperfusion, infarct size was significantly reduced in heat-shocked rats compared with controls (8.4 +/- 1.7%, n = 26 versus 15.5 +/- 1.9%, n = 27; p = 0.007; mean +/- SEM; infarct mass/left ventricular mass x 100). There were no significant differences in left ventricular (LV) systolic pressure, heart rate, LV dP/dt, or rate-pressure product between heat-shocked (n = 11) and control (n = 14) rats during the ischemic period. There were no differences in infarct size between ischemically pretreated and control rats subjected to 35 minutes of ischemia and reperfusion (9.7 +/- 2.1%, n = 23 versus 10.0 +/- 2.1, n = 24; p = NS). CONCLUSIONS. In this model of ischemia and reperfusion, prior heat shock was associated with significantly improved myocardial salvage after 35 minutes of LCA occlusion and reperfusion. This improved salvage was correlated with marked HSP72 induction and was independent of the hemodynamic determinants of myocardial oxygen supply and myocardial oxygen demand during the ischemic period. In contrast, mild HSP72 induction by ischemic pretreatment was not associated with improved myocardial salvage after myocardial ischemia and reperfusion. Thus, the absolute levels of HSP72 may be important in conferring protection from ischemic injury in this animal model.     

Involvement of p38 MAPK and JNK in heat stress-induced cardioprotection

The present study investigated whether heat stress-induced cardioprotection involves alterations in the pattern of p38 mitogen activated protein kinase (p38MAPK) and c-Jun NH2 - terminal kinase (JNK) activation during ischaemia - reperfusion in a model of isolated perfused rat heart. Wistar rats were subjected to whole-body hyperthermia at 42 degrees C for 15 min (HS), while untreated animals served as controls (CON). Twenty four hours later, CON and HS isolated hearts were perfused in a Langendorff mode and subjected to 20 min of zero-.ow global ischaemia followed by 45 min of reperfusion. Postischaemic recovery of left ventricular developed pressure at 45 min of reperfusion was expressed as % of the initial value (LVDP%). Activation of p38 MAPK and JNK was assessed by standard Western blotting techniques using a dual phospho-p38 MAPK and phospho-p46 JNK and p54 JNK antibodies. The levels of phospho-p38 MAPK at the end of reperfusion were not different in HS as compared to CON hearts. The levels of phospho-p46 JNK and p54 JNK were 1.4- and 1.6-fold less in HS than in CON hearts respectively, p < 0.05. LVDP% was 60.3 (s.e.m., 6.3) for HS and 42.9 (4.1) for CON, p < 0.05. In summary, heat stress pretreatment improves postischaemic recovery of function in isolated rat hearts and this is associated with suppressed JNK activation in response to ischaemia-reperfusion.     

Distribution of cardiac output, oxygen consumption and lactate production in canine endotoxin shock

Endotoxin causes shock accompanied by compensatory changes such as redistribution of cardiac output and increased oxygen extraction. We studied these effects in anaesthetised dogs (etomidate: 4 mg X kg-1 X h-1, n = 14) randomly assigned to a control (n = 6) and a shock group (endotoxin 1.5 mg X kg-1; n = 8). We measured left ventricular pressure, LVEDP and LVdP/dt (Millar microtip), mean systemic, central venous and pulmonary artery pressure (Statham P23Db), cardiac output (thermodilution), organ flow (microspheres, 15 micron, 5 labels), bloodgases (PO2, PCO2), pH and lactate. All measurements were performed before and at 60, 90, 120 and 150 min after endotoxin or saline. Sixty minutes after endotoxin mean systemic pressure, LVdP/dt and cardiac output had decreased (by 60, 50 and 35%), while heart rate had increased (by 30%). Arterial PO2 was lower after endotoxin (-29%), haematocrit and mixed venous PCO2 were higher (+16 and +38%) and arterial pH had decreased from 7.34 to 7.14. After endotoxin perfusion of heart and adrenals did not change but muscle perfusion increased (by 33% at t = 90). Endotoxin caused vasoconstriction in spleen and kidneys: the percentage of cardiac output to these organs thus decreased (by 50 and 69%). Sixty minutes after endotoxin we found vasodilatation in the hepatic arterial, pancreatic, and gastrointestinal beds. Later the percentage of cardiac output to these beds decreased. Systemic arterio-venous shunting fell (from 6.5 to 0.7%). Systemic and splanchnic oxygen extraction increased (by 66 and 71% at t = 60): oxygen consumption hardly changed; 60 min after endotoxin it tended to decrease. During shock serum lactate rose (by 167% at t = 60) before oxygen consumption fell. Myocardial oxygen consumption did not alter during shock but the tension time index decreased.     

Hyperthermic pretreatment decreases microvascular protein leakage and attenuates hypotension in anaphylactic shock in rats

Systemic anaphylaxis is a life-threatening allergic reaction and its pathologic conditions, such as edema, bronchospasm, and hypotension, have been attributed to release of vasoactive mediators. Heat shock protein (HSP) is known to play a protective role in living cells under various stresses. In these studies, we investigated the protective role of heat shock response in anaphylactic shock, focusing on changes of blood pressure (BP) and vascular permeability. Adult sensitized rats were injected intravenously with Evans blue (EB) and challenged with bovine serum albumin (BSA). The rats were treated with whole-body hyperthermia at 41.5 +/- 0.5 degrees for 15 min 24 h before BSA challenge. Vascular protein leakage in tissues was analyzed with the EB technique. The results showed that BSA challenge induced EB extravasation in all sensitized rats. EB values (EB/tissue; microg/g) in heart and lung (112.3 +/- 41 and 244.4 +/- 90.6; mean +/- SD; n = 6) in the nonheated rats were significantly higher than those (33.4 +/- 23.3 and 103.4 +/- 63.9; n = 9) in the heated rats (P < 0.05). The results showed that BSA challenge caused BP to fall drastically in the sensitized rats. BP in the heated rats was significantly higher than BP in the nonheated rats from 4 to 15 min during anaphylactic shock (P < 0.001). Inducible HSP72 appeared overexpressed in heart, lung, and liver tissue in the heated rats tested by Western immunoblotting. The results indicate that reduction of increased protein leakage and attenuation of hypotension may result from induction of HSP by whole-body hyperthermia.     

Heat shock response decreases endotoxin-induced acute lung injury in rats

OBJECTIVE: Transient whole-body hyperthermia was reported to reduce lung damage in a rat with intra-abdominal sepsis produced by caecal perforation. METHODOLOGY: In order to determine the effect of heat shock response on acute lung injury induced by endotoxin, which plays a central role in the pathogenesis of sepsis, we instilled either saline or lipopolysaccharide (LPS) intravenously with and without heat pretreatment in rats. The heated rats had their rectal temperature raised to more than 40 degrees C for 13 min 18 h before intravenous administration of saline or LPS. RESULTS: We found that the lung leak was significantly increased among the rats given LPS intravenously with (median, 0.17; range, 0.15-0.22; n = 10) and without heat pretreatment (0.23; 0.17-0.30; n = 10) compared with those of saline-treated rats (0.13; 0.10-0.14; n = 10) (P < 0.05 in each). However, rats given LPS after heat pretreatment had significantly decreased lung leak index compared with those of LPS-treated rats without heat pretreatment (P < 0.05). Rats administered LPS intravenously showed increased myeloperoxidase activity without heat pretreatment (19.01; 9.34-28.00 U/g; n = 10) compared with that of saline-treated rats (7.09; 4.49-10.56 U/g; n = 5) (P < 0.05) (Fig. 2). Myeloperoxidase activity of the rats treated with LPS with heat pretreatment (5.57; 2.87-8.96 U/g; n = 10) was significantly decreased to the level of normal control compared with that of LPS-treated rats without heat pretreatment (P < 0.05). The levels of heat shock proteins (HSP72) in lung tissue, which were examined by western blot analysis, were increased over baseline levels at 23 h after hyperthermic stress. CONCLUSIONS: These observations show that brief heat shock response is associated with the induction of HSP72 protein synthesis and attenuated neutrophil recruitment and acute lung leak is induced by endotoxin in rats.     

Developmental changes in tolerance to ischaemia in the rabbit heart: disparity between interpretations of structural, enzymatic and functional indices of injury.

The vulnerability of the heart to injury during ischaemia and reperfusion and its responsiveness to various protective and pharmacological interventions are age-dependent. Using three independent indices of tissue injury (cardiac structure, contractile function and creatine kinase leakage), we compared the response of adult (60-90 days old) and neonatal (7 days old) isolated perfused rabbit hearts to global ischaemia and reperfusion. Prior to ischaemia, heart rate was significantly higher in neonatal hearts, as were control values for coronary flow, aortic flow and cardiac output when expressed on a dry wt basis. In experiments in which adult and neonatal hearts (n = 8 per group) were subjected to 2 min of cardioplegia and 45 min of ischaemia, the post-ischaemic recovery of all indices of cardiac function (when expressed as a percentage of pre-ischaemic control) was significantly higher in neonatal than in adult hearts. Thus, cardiac output recovered to 82.9 +/- 3.6% in the neonate but to only 57.9 +/- 6.7% in the adult (P < 0.05). The functional evidence of a greater resistance to ischaemia in the neonate was, however, contradicted by the levels of creatine kinase leakage which tended to be greater in the neonatal than in the adult heart (32.0 +/- 4.7 vs 20.0 +/- 3.1 IU/15 min/g dry wt). Morphological studies indicated that injury was comparable (moderate-to-severe in degree) in both groups. To assess further the relationship between the three indices, additional experiments were undertaken in which the duration of ischaemia in the neonate was extended to 60 min so that the post-ischaemic recovery of function was reduced to a level similar to that seen in the adult after 45 min of ischaemia. Under these conditions cardiac output recovered to 55.6 +/- 4.8% in the neonatal heart (P = NS when compared with the adult) and creatine kinase leakage increased to 88.2 +/- 13.9 IU/15 min/g dry wt--a value over four times greater than that measured in adult hearts with a comparable degree of functional injury. Morphological examination of tissue obtained after 15 min of reperfusion revealed a remarkable recovery of structure in both age groups. In conclusion, in functional terms the neonatal heart was more resistant to ischaemia than the adult; enzymic leakage, however, indicated the opposite and structural assessment revealed no differences. Thus, in comparing injury during ischaemia and reperfusion between different age groups, it is clearly important to employ several independent indices.     

Increased levels of serum follicle-stimulating hormone and luteinizing hormone associated with intrinsic testicular hyperthermia in oligospermic infertile men

A Negative correlation between spermatozoa output and serum gonadotropin levels, as well as between scrotal temperature and spermatozoa output, has been found in man. However, no studies have been done on the relationship between scrotal temperature and serum gonadotropin levels. This paper reports such data from 212 infertile men. The upper limit for normal scrotal temperature was defined as the 90th percentile value (35.3 C) of a control group of 64 fertile men whose mean serum FSH and LH levels were 6.0 +/- 0.8 (+/- SE) and 6.4 +/- 0.7 IU/L, respectively. This value for scrotal temperature (35.3 C) was used to classify infertile men into 3 groups: bilateral hyperthermia (n = 56), unilateral hyperthermia (n = 40), and bilateral normothermia (n = 116). In the unilateral and bilateral hyperthermic groups serum LH and FSH levels were significantly increased compared with those in the normothermic group. The mean serum testosterone values were similar in all groups. To study the relationships between serum gonadotropin levels or spermatozoa output and scrotal temperature, the infertile men also were divided into classes according to their spermatozoa output. These classes were subdivided into two groups, normothermic or hyperthermic, according to whether the left scrotal temperature was equal to or less than, or more than 35.3 C. For the infertile men whose spermatozoa output was more than 60 X 10(6) spermatozoa/ejaculate (normospermia), there was no significant difference between the serum gonadotropin levels of the normothermic (n = 42) and the hyperthermic (n = 20) groups. Among the oligospermic men (spermatozoa output, 0.1-60 X 10(6) spermatozoa/ejaculate), the hyperthermic group (n = 65) had significantly higher serum gonadotropin levels and significantly smaller testicular volumes than the normothermic group (n = 71). The two oligospermic groups also had significantly higher serum FSH values than the infertile normospermic groups. These results were not linked to the presence of a varicocele or a history of cryptorchidism, as the prevalence of varicocele and cryptorchidism was equally distributed within the groups studied. We conclude that the increase in serum gonadotropin levels in the case of a decrease in spermatozoa output is significantly greater in the presence of associated scrotal hyperthermia.     

Acute effects of amiodarone on ultrastructure and electrical activity of isolated guinea pig hearts.

STUDY OBJECTIVE--The aim was to evaluate the effects of tissue concentration of amiodarone on ultrastructure and electrical activity in isolated spontaneously beating Langendorff perfused guinea pig hearts. DESIGN--Group 1: The influence of 10 microM amiodarone over a period of 1 h in a non-recirculated perfusate on conduction intervals, heart rate, creatine kinase concentration in the coronary effluent, coronary flow, and drug accumulation was determined. Group 2: Ultrastructural changes after 30 min and 60 min perfusion with amiodarone were examined. Group 3: Cardiac refractoriness was evaluated following 30 min and 60 min of perfusion with amiodarone. EXPERIMENTAL PREPARATIONS--Isolated hearts of guinea pigs (200-300 g) were used: group 1, n = 6 animals; group 2, n = 3 for each time span; and group 3, n = 6 for each time span. MEASUREMENTS AND MAIN RESULTS--A steady state for the effects of amiodarone on atrioventricular and intraventricular conduction [+31(SEM 5)%, p less than 0.01% +47(12)%, p less than 0.01, respectively] and on heart rate [-30(9)%, p less than 0.01] was reached after 15 min, and on His bundle conduction [+38(17)%, p less than 0.01] after 30 min. QT duration was not affected throughout the duration of the experiment. Cardiac refractoriness was significantly prolonged following 30 min perfusion with 10 microM amiodarone, and was further significantly increased following 60 min perfusion. Amiodarone tissue concentration increased to 365(39) nmol.g-1 wet weight, and this was accompanied by an increase in creatine kinase concentration in the coronary effluent. Coronary flow stayed constant throughout the whole experiment. At the end of the experiment electron microscopic examination of the myocardium of the left ventricle showed accumulation, fusion, and vacuolisation of mitochondria, and perinuclear oedema. CONCLUSIONS--These observations suggest that amiodarone, as well as exerting acute electrophysiological effects, creates ultrastructural changes which probably contribute to its effectiveness in arrhythmias caused by scarred myocardium.     

Postischemic reperfusion injury can be attenuated by oxygen tension control

Oxygen-derived free radicals cause cytotoxic damage during reperfusion after a period of ischemia and the production of these free radicals may be proportionate to oxygen tension (PO2). The present study tested the hypothesis that oxidative damage may be limited by maintaining a more physiologic PO2 following ischemia. An experimental study in Wistar rats were mounted on a Langendorff apparatus was conducted to estimate baseline aortic flow (AF), coronary flow (CF), cardiac output (CO), systolic pressure (SP), heart rate (HR), and the rate-pressure product (RPP: HRxSP). The hearts were divided into 3 groups (n=7, hearts/group): group 1, hypoxic (PO2=300+/-50 mmHg) reperfusion; group 2, middleoxic (PO2=500+/-50 mmHg) reperfusion; and group 3, hyperoxic (PO2=700+/-50 mmHg) reperfusion. Following 30 min of warm ischemia, hearts in all groups were reperfused at each oxygen pressure. The recovery of cardiac function of each heart was measured at the end of reperfusion. Concentrations of lactate (LAC), lactate dehydrogenase (LDH), and creatine kinase (CK) in the coronary perfusate during reperfusion were measured. The recovery rate of CO, SP, and RPP in group 2 were all significantly better than in the other 2 groups. CK leakage in group 2 was significantly lower than in group 3. A clinical study was also conducted during elective coronary artery bypass grafts in 16 consecutive patients who underwent either hyperoxic (n=8, PO2=450-550 mmHg) or more physiologic (n=8, PO2=200-250 mmHg) cardiopulmonary bypass after aortic unclamping. The clinical study assessed CK-MB, LDH, LAC, and malondialdehyde (MDA) in patient blood prior to starting the surgical procedure and at 30 min and 3, 9, and 21 h after unclamping. Cardiac index (CI), central venous pressure, pulmonary capillary wedge pressure, systolic arterial pressure, and the dose of cathecholamines were also measured. Although no significant differences were present in the dose of cathecholamines, the CI in the more physiologic oxygen tension group was significantly higher than in the hyperoxic group at 3 and 6 h after unclamping. The levels of MDA in the more physiologic PO2 group was significantly lower at 30 min after aortic unclamping than in the hyperoxic group. The present results suggest that in the experimental as well as in the clinical study, high PO2 leads to myocardial reperfusion damage; however, maintaining a more physiologic PO2 during reperfusion following ischemia may attenuate reperfusion injury.     

A proteasome inhibitor confers cardioprotection

OBJECTIVE: In several cell types, proteasome inhibitors like carbobenzoxyl-leucinyl-leucinyl-leucinal (MG132) induce the 72 kDa heat shock protein (Hsp72) and exert cell protective effects. However, data in cardiomyocytes are currently lacking. METHODS AND RESULTS: We investigated the effects of MG132 in cultured neonatal rat cardiomyocytes. MG132 time- and concentration-dependently induced Hsp72 and Hsp32 at mRNA and protein levels. Although Hsp60 mRNA was induced, Hsp60 protein levels were not altered. MG132 activated p38 MAP kinase already after 0.5 h. Hsp mRNA induction started after 2 h of MG132 treatment. Subsequently, Hsp72 and Hsp32 protein levels were increased after 4 h. SB202190, an inhibitor of p38 MAP kinase, concentration-dependently attenuated MG132-induced Hsp72-and Hsp32-elevations (by 59% and 41%, respectively, at 1 microM SB202190). In contrast, herbimycin A, a known inductor of Hsp72 in cardiomyocytes, enhanced the MG132-induced Hsp72 and Hsp32 expression even further: additionally applied 2 microM herbimycin A induced Hsp72 and Hsp32 about 2-fold higher than 1 microM MG132 alone. MG132 (1 microM) decreased the hyperthermia- or hydrogen peroxide-induced release of lactate dehydrogenase by 45% and by 35%, respectively (P<0.05, n=5). MG132 (1 microM) prolonged the spontaneous beating time of cardiomyocytes at 46 degrees C from 5+/-2 min (control hyperthermia) to 28+/-5 min (P<0.05, n=4). Thus, inhibition of the proteasome function by MG132 protects cardiomyocytes against hyperthermic or oxidative injury. This protective effect and Hsp induction were abolished by 1 microM SB202190. CONCLUSION: Proteasome inhibition results in p38 MAP kinase-dependent induction of Hsp72 and Hsp32 and might be a novel cardioprotective modality.     

Renal function and metabolism during endotoxemia in rats: role of hypoperfusion.

Renal failure often complicates endotoxin shock. This might be due to renal hypoperfusion, but endotoxemia could also have additional effects. We studied in anesthetized rats renal plasma flow (RPF), glomerular filtration rate (GFR), and metabolism (ATP, CrP = creatine phosphate, energy charge = [ATP + 0.5 ADP]/[ATP + ADP + AMP], lactate, glucose) during endotoxin shock (Escherichia coli endotoxin, 10 mg/kg for 60 min; n = 10) and "balloon shock" (balloon inflated in vena cava below renal vein to cause comparable decreases in cardiac output and RPF as in endotoxin-treated rats; n = 10). A third group of rats served as controls (n = 10). At t = 0 infusion of endotoxin was started. At t = 90 min, when cardiac output was low and serum lactate was high (indicating shock), GFR and RPF were obtained from plasma disappearance rates (from t = 90 to t = 135 min) of 125I-thalamate and 131I-hippurate, respectively. Experiments ended at t = 135 min. In both shock groups RPF decreased (by ca. - 75% compared with control rats), but filtration fraction only increased (by 72%) in the "balloon shock" rats. In renal biopsies lactate concentration increased more (by 407 vs. 167%) and ATP decreased more (by -63 vs. - 35%) during endotoxin shock than during "balloon shock"; the endotoxin-treated rats also showed a significant decrease in CrP (by - 58%), energy charge (by - 31%), and glucose concentration (by - 34%), and an increase in the number of leukocytes in the glomeruli (by 730%). Renal function and metabolism thus was more affected in this hypodynamic form of endotoxin shock than in "balloon shock." This may be caused by the effects of endotoxin on sticking of leukocytes and renal metabolism.     

Whole body heat stress fails to limit infarct size in the reperfused rabbit heart.

OBJECTIVE: It has recently been shown that induction of heat stress proteins by whole body heat stress confers myocardial protection in the isolated in vitro rat and rabbit heart. This study extends the above studies by examining the effects of stress protein synthesis on the limitation of infarct size in the in vivo rabbit heart model. METHODS: 30 male New Zealand white rabbits were used. Six rabbits were used for measurement of heat stress protein; 10 were used for infarct size determination in a heat stress group (HS); 14 were used for infarct size determination in a control group. There were 10 exclusions. Under anaesthesia, body temperature was raised to 42 degrees C for 15 min in the HS group. Following 24 hours of recovery rabbits were reanaesthetised and the hearts subjected to a 45 min period of regional ischaemia followed by 3 h reperfusion. The risk zone was defined with fluorescent particles and the infarct area determined by tetrazolium staining. Western blotting showed an increase in the 72 KD heat stress protein in hearts in the HS group. RESULTS: Infarct size as a percent of risk area was 61.4 (SEM 6.4)% (n = 14) in control hearts and 71.8(7.3)% (n = 10) in the HS hearts. These results were not statistically significant. CONCLUSIONS: No protective effect of heat stress could be seen when infarct size was used as the end point. Either the protection seen in earlier studies using the Krebs perfused isolated heart model does not accurately reflect protection against myocardial infarction, or heat stress itself may induce injurious factors in the blood which will negate any direct protective effect to the myocardium in this model.     

Infarct size determination using enzymatic methods in patients with early coronary recanalization

To evaluate the usefulness of the infarct size determined by serial creatine kinase (CPK) measurements in patients with early reperfusion, we have studied 189 patients meaning in age 59.2 +/- 8.6 years, with acute myocardial infarction treated with streptokinase (STK); 81 of them by intracoronary route (group A), and 108 by intravenous administration (group B). In the group A we performed serial angiographic studies in the following conditions: baseline, immediately after STK infusion and before hospital discharge. In group B we performed only one angiographic control 5 +/- 3 days after. In patients with reperfusion, the parameters of left ventricular function correlated with cumulative creatine kinase release (MAX-CPKr) by linear regression in both groups. We observed a tendency to closer correlations in patients with left anterior descending or circumflex artery as the infarct related artery, in patients without previous infarction and in those who did not receive electrical shock for ventricular arrhythmias. In patients with unsuccessful reperfusion (n = 11), we also obtain a significant correlation (r = 0.72) between ejection fraction and MAX-CPKr. The slope of the regression line (b = 7.7 X 10(-5) was steeper (p less than 0.05) than that observed in recanalized patients, who were evaluated within the first 3 days (b = 2.2 X 10(-5), after 8 +/- 5 days (b = 2.7 X 10(-5), or before discharge, at 22 +/- 9 days (b = 2.6 X 10(-5).(ABSTRACT TRUNCATED AT 250 WORDS)     

热休克对再灌注性心律失常的影响及其作用机制的研究

目的研究热休克预处理对SD大鼠再灌注性心律失常的影响及其作用机制。 方法将32只SD大鼠随机分为热休克组(n=16)和对照组(n=16)。热休克组大鼠给予热休克预处理而对照组则否。采用Langendorff离体心脏灌注法,先稳定灌注40分,再停灌20分,然后复灌60分。心电图记录再灌注时心律失常情况。并检测再灌注时心脏流出液肌酸激酶(CK)的活性。以Westernblot法检测两组心脏组织中70KD热休克蛋白(HSP70)的相对含量。另外还检测心肌组织中的超氧化物歧化酶(SOD)、谷胱甘肽过氧化物酶(GSH-Px)和过氧化氢酶(CAT)等抗氧化酶的活性,及脂质过氧化物丙二醛(MDA)的含量。 结果热休克组的再灌注性心律失常发生率明显较对照组为低,表现为心室颤动发生率在热休克组为0,而对照组为6/16。室性心动过速发生率热休克组为3/16,而对照组为7/16,以热休克组为低(P＜0.05)。再灌注过程中心肌CK的释放量热休克组31.4±6.8IU/L较对照组42.3±8.9IU/L显著减少(P＜0.001)。热休克组心脏组织HSP70表达量较对照组显著增多,信号条带积分吸光值热休克组为6.39±1.98,对照组为4.62±2.05(P＜0.01)。热休克组抗氧化酶活性较对照组明显增强,而脂质过氧化物则降低。 结论热休克预处理可以减轻SD大鼠心肌再灌注性损伤,减少再灌注性心律失常的发生,此作用与心脏组织中HSP70含量的增加和抗氧化酶活性的显著增强有关。     

Potentiation of baroreceptor reflex response by heat shock protein 70 in nucleus tractus solitarii confers cardiovascular protection during heatstroke

BACKGROUND: Whereas hypotension and bradycardia seen during the onset of heatstroke may be protected by prior induction of heat shock protein 70 (HSP70) in the brain, the underlying mechanism is not fully understood. We evaluated the hypothesis that HSP70 may confer cardiovascular protection during heatstroke by potentiating the baroreceptor reflex (BRR) control of peripheral hemodynamic performance. METHODS AND RESULTS: Adult male Sprague-Dawley rats subjected to a brief hyperthermic heat shock (HS; 42 degrees C for 15 minutes) induced discernible expression of HSP70 in the bilateral nucleus tractus solitarii (NTS), the terminal site in the brain stem for primary baroreceptor afferents. This HSP70 expression was detected at 8 hours, peaked at 24 hours, and returned to baseline by 48 hours after HS. Brief hyperthermia also significantly potentiated the BRR response in a temporal profile that correlated positively with changes in HSP70 expression at the NTS. Prior HS also appreciably alleviated hyperthermia, severe hypotension, and bradycardia manifested during the onset of heatstroke (45 degrees C for 60 minutes) elicited 24 hours later. Microinjection bilaterally of anti-HSP70 antiserum (1:20) into the NTS or denervation of the sinoaortic baroreceptor afferents significantly reversed the enhancement of BRR response and cardiovascular protection during heatstroke induced by prior HS. CONCLUSIONS: These results suggest that HS-induced expression of HSP70 in the NTS may alleviate severe hypotension and bradycardia exhibited during the onset of heatstroke by potentiating both the sensitivity and capacity of BRR response.     

Endocannabinoids are implicated in the infarct size-reducing effect conferred by heat stress preconditioning in isolated rat hearts

OBJECTIVE: We have investigated the involvement of the endocannabinoid system in the delayed cardioprotection conferred by heat stress preconditioning in the isolated rat heart. METHODS: Rats were divided into eight groups (n=7 in each group), subjected to either heat stress (42 degrees C for 15 min, HS groups) or sham anaesthesia (Sham groups). Twenty-four hours later, their hearts were isolated, retrogradely perfused, and subjected to a 30-min occlusion of the left coronary artery followed by 120 min of reperfusion. Some hearts were perfused with either SR 141716 (a cannabinoid CB(1) receptor antagonist, 1 microM), SR 144528 (a CB(2) receptor antagonist, 1 microM) or L-NAME (a NOS inhibitor, 3 microM) 5 min before ischaemia and during the ischaemic period. RESULTS: The infarct size-reducing effect conferred by heat stress (35.7+/-1.8% in Sham to 14.1+/-0.6% in HS groups) was not altered by the perfusion of SR 141716 (11.2+/-1.5%) but was abolished by both SR 144528 (36.6+/-1.6%) and L-NAME (32.0+/-4.4%). In hearts from non-heat-stressed rats, perfusion with SR 141716 (32.8+/-1.6%), SR 144528 (33.4+/-2.2%) and L-NAME (31.6+/-2.9%) had no effect on infarct size. CONCLUSION: These results suggest an involvement of endocannabinoids, acting through CB(2) receptors, and NO in the cardioprotection conferred by heat stress against myocardial ischaemia. The possible interaction between both mediators of the heat stress response remains to be determined.     

The energetics of myocardial stretch. Creatine kinase flux and oxygen consumption in the noncontracting rat heart

Previous studies have suggested that flux through the creatine kinase reaction is coupled to cardiac performance and to the rate of adenosine triphosphate synthesis in the intact, beating heart. To define the effect of passive myocardial stretch on creatine kinase kinetics, we measured the rate constants and chemical fluxes for both directions of the creatine kinase reaction with the 31P-nuclear magnetic resonance technique of magnetization transfer in isolated, arrested rat hearts at four levels of left ventricular pressure and volume. Adenosine triphosphate synthesis was estimated from oxygen consumption measurements. As left ventricular pressure rose from 0 to 24 mm Hg and oxygen consumption increased by 20%, we observed a twofold increase in the rate constants and fluxes (mean +/- SD, n = 4-7) for the creatine kinase reaction. The forward rate constant increased from 0.33 +/- 0.03 to 0.80 +/- 0.08, and the reverse rate increased from 0.34 +/- 0.11 to 0.74 +/- 0.32/sec. The forward and reverse fluxes for the creatine kinase reaction increased from 12.0 +/- 3.4 to 26.5 +/- 5.8 and from 9.1 +/- 3.4 to 19.1 +/- 3.4 mumol/g dry weight per sec, respectively. At each level of left ventricular pressure, the forward and reverse rate constants were the same. However, as left ventricular pressure increased, the ratio of the forward to the apparent reverse fluxes for the creatine kinase reaction increased. The relationships between the rate constant or flux through the creatine kinase reaction vs. left ventricular pressure were linear. In addition to providing further support for the coupling between creatine kinase and mitochondrial adenosine triphosphate synthesis, these results suggest that flux through the creatine kinase reaction and adenosine triphosphate synthesis increases with myocardial stretch in the intact, noncontracting heart.     

急性心肌梗死中缺血预适应可否保护心肌

目的探讨心肌梗死前心绞痛对心肌产生的缺血预适应,对行经皮冠状动脉介入术急性心肌梗死患者是否有近期及远期的保护作用。方法急性心肌梗死113例,介入术组(68例)行急诊经皮冠状动脉介入术,非介入术组(45例)没行再灌注治疗。观察急性心肌梗死前48h有否心绞痛发作,再分为心绞痛阳性和心绞痛阴性两亚组。观察两组患者的预后。结果介入术组的心绞痛阳性和心绞痛阴性两亚组住院期间心力衰竭、心源性休克、心肌酶峰值、心源性死亡、左室射血分数以及随诊期心力衰竭、心绞痛发生率、心源性死亡的差异无统计学意义(P>0.05);非介入术组的AP阳性亚组住院期间心力衰竭、心源性休克、心肌酶峰值及达峰时间均较低、左室射血分数较高,差异有统计学意义(P<0.05),随诊期心绞痛发生率、心源性死亡似有增高趋势,但差异无统计学意义(P>0.05)。结论心肌梗死前心绞痛对行经皮冠状动脉介入术的急性心肌梗死患者保护作用不显著,对没行再灌注治疗的急性心肌梗死患者,可改善近期预后,但远期保护作用不明显。     

The effect of ethanol on survival time in hemorrhagic shock in an unanesthetized swine model

Controversy exists as to whether ethanol intoxication causes exaggerated hypotension or increased mortality during hemorrhagic shock. Previous studies have used anesthetized animals. This limits data interpretation as anesthetic agents, particularly pentobarbital, have well-documented effects on hemodynamics and the response to hemorrhage. We studied the effects of moderate ethanol intoxication on blood pressure and survival time during fatal hemorrhagic shock in unanesthetized swine. Immature female swine weighing 15 to 20 kg were splenectomized and instrumented with chronic indwelling aortic catheters, right atrial catheters, and gastrostomy tubes. Four to seven days later the unanesthetized animals underwent hemorrhagic shock. Thirty minutes prior to the start of hemorrhage, the experimental group (n = 8) received 3 mL/kg of 100% ethanol mixed as a 1:3 solution with water through a gastrostomy tube. The control group (n = 8) received an equal amount of water. The distal aortic catheter was connected to a roller pump and blood was removed at a rate of 1 mL/kg/min until the animal died. Arterial pressure, heart rate, lactate ethanol and glucose levels, hematocrit, and arterial blood gases were measured in both groups at baseline and every 15 minutes thereafter. A mean ethanol level of 1,500 to 1,700 micrograms/mL was produced in the experimental group from baseline through 60 minutes. Data were analyzed using Student's two-tailed t test, and analysis of variance for repeated measures. There was no significant difference in survival time between the control (63.1 +/- 2.8 min) and ethanol (59.9 +/- 5.9 min) groups. Systolic blood pressure was significantly lower in the ethanol group after 15 minutes of hemorrhage (81 +/- 22 to 59 +/- 14 mm Hg, P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)