NADH Fluorescence Photography Research Articles

Studies on the cardiotoxicity of noradrenaline in isolated rabbit hearts.

The concentration-dependent toxic effects of exogenous noradrenaline (NA, CAS 51-41-2) on acute regional myocardial ischemia (MI) was investigated with and without alpha- and beta-adrenoceptor blockade. Electrically-driven rabbit Langendorff-hearts with depleted catecholamine stores were used (reserpin 7.0 mg/kg i.p. 16-24 h before preparation, constant pressure: 70 cm H2O, Tyrode solution, Ca2+ 1.8 mmol/l). Repetitive MI, separated by a reperfusion period of 50 min, was induced by coronary artery branch ligature, and quantitated from epicardial NADH-fluorescence photography. Starting after a reperfusion period of 20 min, hearts were treated with exogenous NA (10(-7), 10(-6) or 10(-5) mol/l). Adrenoceptors were blocked by propranolol (10(-6) mol/l) and phentolamine (10(-6) mol/l). Without adrenoceptor blockers, NA 10(-6) mol/l induced an increase in left ventricular pressure and a reduction in the relative coronary flow. Concomitantly, MI was enhanced. After adrenoceptor blockade, NA 10(-7) or 10(-6) mol/l had no influence on functional parameters. MI was not affected by NA 10(-7) mol/l, but MI was significantly enhanced by NA 10(-6) mol/l. MI enhancement by NA 10(-6) mol/l was completely prevented by superoxide dismutase (30 U/ml). Functional effects of NA 10(-5) mol/l were not completely inhibited by adrenoceptor blockers at the concentrations used, and arrythmias were observed. MI was also enhanced by NA 10(-5) mol/l. Deleterious effects on MI, that are independent on functional effects, are induced by NA in a micromolar concentration. These direct toxic effects are mediated by superoxide anion radicals. In lower concentrations (10(-7) mol/l), there is no evidence for direct toxic actions of NA independent of functional effects. MI enhancement by NA 10(-5), or 10(-6) mol/l without adrenoceptor blockers may have been caused in part by functional and arrythmogenic effects and/or through the generation of oxygen free radicals.

Studies on the Role of Superoxide Anion Radicals for the Cardiotoxicity of Adrenochrome

Adrenochrome is an oxidative product of adrenaline and possesses cardiotoxic properties. As oxygen free radicals play a role in the cytotoxic effects of catecholamines, the role of superoxide anion radicals, as mediators of adrenochrome toxicity, was investigated using electrically-driven Langendorff rabbit hearts with depleted catecholamine stores. Repetitive regional myocardial ischemia (MI) was induced by coronary artery branch ligature, and MI was quantitated from epicardial NADH-fluorescence photography. Adrenochrome (10(-6) mol/l) was added to the perfusion solution after a reperfusion period of 20 min, 30 min before the 2nd coronary occlusion, with or without the additional application of SOD (30 U/ml). Left ventricular pressure was significantly enhanced by adrenochrome (p < 0.05), but it fell rapidly down below its initial value (p < 0.05). Coronary flow was significantly decreased by adrenochrome (p < 0.05). Whereas epicardial NADH-fluorescence was similar after repetitive coronary occlusions in untreated controls, it was significantly enhanced by adrenochrome (p < 0.05). The deleterious effects of adrenochrome on MI were not inhibited by SOD. Thus, there is no evidence for superoxide anion radicals as mediators of the deleterious effects of adrenochrome on MI in isolated rabbit hearts. The deleterious effects of adrenochrome on MI in isolated rabbit hearts might be caused by functional effects, impairing the oxygen consumption/oxygen supply balance.

Flow-Independent Myocardial Ischemia Induced by Endothelin-1

The endothelin-1 (ET-1) is known to cause myocardial ischemia; however, whether this effect is entirely dependent on vasoconstriction is uncertain. The aim of this study was to characterize the myocardial ischemia after the intracoronary administration of endothelin-1, and compare it with that induced by coronary stenosis. In the left anterior descending coronary artery of 15 dogs, a mild inflow reduction (30%) was produced for 10 minutes using intracoronary endothelin-1 (46 +/- 33 pmol/min) or coronary stenosis. The hearts were rapidly cross-sectioned at short axial plane and freeze-clamped within 120 milliseconds using a specially developed device to visualize and quantify the area of ischemia (%IA) with NADH fluorescence photography. The %IA was larger in the endothelin-1 group than in the stenosis group (66 +/- 23 versus 18 +/- 18, P = 0.0005); furthermore, the ischemia was transmural in the ET-1 group, but limited to subendocardium in the stenosis group. ET-1 increased the coronary arterial resistance especially in subepicardial region and produced smaller ischemic foci in microcirculation. The mechanism of larger ischemia produced by ET-1 might depend on pro-ischemic effects on myocytes and vasoconstriction of the coronary microcirculation, predominantly in the subepicardium in vivo.

Functional and antiischaemic effects of monoacetyl-vitexinrhamnoside in different in vitro models

1. 1. Functional and antiischaemic effects of monoacetyl-vitexinrhamnoside (AVR), a flavonoid with phosphodiesterase (PDE)-inhibitory properties contained in Crataegus species (Hawthorn, Rosaceae) were studied in several in-vitro models. 2. 2. In rabbit isolated femoral artery rings, AVR concentration-dependently reduced developed tension. Vasodilation by AVR was reduced after inhibiting EDRF formation by L-N G-nitro arginine. 3. 3. In spontaneously-beating Langendorff-guinea pig hearts, AVR concentration-dependently enhanced heart-rate, contractility, lusitropy and coronary flow. 4. 4. In isolated electrically-driven Langendorff-rabbit hearts, acute regional ischemia (MI) was induced by coronary artery occlusion and quantified from epicardial NADH-fluorescence photography. AVR (5 × 10 −5 mol/l) induced a slight numerical increase of left ventricular pressure and coronary flow ( p > 0.05). MI was reduced ( p < 0.05). 5. 5. Monoacetyl-vitexinrhamnoside is an inodilator whose vasodilatory action may be mediated in part by EDRF in addition to PDE-inhibition. Monoacetyl-vitexinrhamnoside does possess marked antiischemic properties even in isolated hearts, suggesting an improvement of myocardial perfusion.

Effects of different inotropes with antioxidant properties on acute regional myocardial ischemia in isolated rabbit hearts

1. 1. The antiischemic properties of the flavonóids acetylvitexin-rhamnoside (AVR) and luteolin-7-glucoside-(LUT), combining phosphodiesterase (PDE)-inhibitory and antioxidant properties, were studied in comparison to amrinone (AMR) or superoxide dismutase (SOD). The effects of the new dihydropyridine-type calcium-agonist Bay T 5006 were studied in comparison to Bay K 8644. 2. 2. In isolated Langendorff-rabbit hearts perfused at constant pressure, acute regional ischemia (MI) was induced by coronary artery occlusion (CAO) and quantitated from epicardial NADH-fluorescence photography. Drugs were applied either before or after CAO (pre-treatment or treatment) to permit distinguishing the influence of functional and direct cytoprotective actions in the poorly collateralized rabbit hearts. 3. 3. SOD did not affect left ventricular pressure (LVP) or coronary flow (CF) and reduced MI only if applied before CAO. LVP and CF were enhanced by LUT or AMR but not by AVR. MI was reduced to a similar extent in hearts treated with either drug. Cardioprotection by LUT was not improved by starting drug application before CAO. 4. 4. Bay K 8644 reduced LVP and particularly CF, whereas Bay T 5006 did not affect functional parameters. MI was enlarged by Bay K 8644 and remained unaffected by treatment or pretreatment with Bay T 5006. 5. 5. AMR, LUT and AVR possess antiischemic properties related to an improvement of myocardial perfusion. Although oxygen free radicals contribute to ischemic tissue injury, as shown by the cardioprotective effectiveness of SOD, antioxidant properties of the flavonoids LUT and AVR do not seem to be relevant for the antiischemic effects. Our findings also give no evidence for antioxidant properties of dihydropyridines relevant for cardioprotection.

Functional and antiischemic effects of luteolin-7-glucoside in isolated rabbit hearts

1. The functional effects of the flavonoid luteolin-7-glucoside (LUT) were investigated in Langendorff-rabbit hearts perfused at constant pressure. Repetitive myocardial ischemia was induced by coronary artery ligature and quantified from NADH-fluorescence photography. 2. LUT significantly enhanced left ventricular pressure and the global and relative coronary flow (= global coronary flow/pressure — rate product). 3. LUT significantly diminished epicardial NADH-fluorescence area and intensity. 4. LUT is an inodilator possessing cardioprotective properties. These might be related to an improvement of myocardial perfusion and/or to free radical scavenging properties.

Cardiotoxicity of adrenochrome in isolated rabbit hearts assessed by epicardial NADH fluorescence.

Noradrenaline in a micromolar concentration has recently been shown to contribute to ischemic tissue injury by direct cardiotoxic effects independent of functional alterations. Oxygen free radicals, generated during the auto-oxidation of catecholamines, are important mediators of catecholamine cardiotoxicity. However, the role of the oxidative products (aminochromes) is still unclear. We examined the effects of adrenochrome on functional parameters and on regional myocardial ischemia (MI) in isolated electrically-driven rabbit hearts with depleted catecholamine stores (reserpine 7.0 mg/kg i.p. 16-24 h before preparation, Langendorff, constant pressure: 70 cm H2O, Tyrode solution, Ca++ 1.8 mmol/l, 37 degrees C). Repetitive MI, separated by a reperfusion period of 50 min, was induced by coronary artery branch ligature, and MI was quantitated from epicardial NADH fluorescence photography. Adrenochrome-treatment (10(-6) M or 10(-4) M) was started after a reperfusion period of 20 min. The left ventricular pressure (LVP) was significantly enhanced by adrenochrome (p < 0.05), but it fell thereafter to below its initial value in hearts treated with adrenochrome 10(-4) M. The global coronary flow (CF) was not affected by adrenochrome 10(-6) M (P > 0.05), but it was significantly decreased by adrenochrome 10(-4) M (P < 0.05). The relative CF (= CF/LVP x heart-rate) was numerically decreased by adrenochrome 10(-6) M (p > 0.05) and more markedly by adrenochrome 10(-4) M (p < 0.05). Whereas epicardial NADH fluorescence was similar after repetitive coronary artery occlusions in controls and in hearts treated with adrenochrome 10(-6) M (p > 0.05), it was significantly enhanced by adrenochrome 10(-4) M (p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

A quantitative comparison of functional and anti‐ischaemic effects of the phosphodiesterase‐inhibitors, amrinone, milrinone and levosimendan in rabbit isolated hearts

1. The functional and anti-ischaemic effects of the phosphodiesterase (PDE)-inhibitors, amrinone, milrinone and levosimendan, a new agent combining PDE-inhibitory with calcium-sensitizing properties, were investigated in rabbit isolated hearts (Langendorff, constant pressure: 70 cmH2O, Tyrode solution, Ca2+ 1.8 mmol l-1, 37 degrees C). Anti-ischaemic effects were studied in electrically-driven hearts (200 beats min-1). Acute regional ischaemia was induced by ligature of a branch of the circumflex coronary artery and quantified from epicardial NADH-fluorescence photography. 2. Cumulative concentration-response curves in spontaneously beating hearts in the presence of isoprenaline (10(-10) M), showed a higher inotropic and coronary vasodilator potency for levosimendan (EC50: 7 x 10(-7) M) compared to milrinone (EC50: 7.7 x 10(-6) M) or amrinone (EC50: 2 x 10(-5) M). Although the maximal coronary dilator activity was similar for the three agents, the maximal inotropic and chronotropic effects were lower for levosimendan than for amrinone or milrinone (P < 0.05). 3. In regionally ischaemic hearts, milrinone (10(-5) M) or levosimendan (5 x 10(-6) M) similarly enhanced the left ventricular pressure (+15-20%) (P < 0.05) and the global coronary flow (+40-50%) (P < 0.05). The epicardial NADH-fluorescence area was significantly diminished by milrinone or levosimendan (-20-30%) (P < 0.05) and there was no significant difference between the anti-ischaemic effects of either agent (P > 0.05). 4. It is concluded that amrinone and milrinone possess similar functional profiles in rabbit isolated hearts and a higher inotropic and chronotropic efficacy than levosimendan. At functionally equieffective concentrations, milrinone and levosimendan show similar anti-ischaemic effects, related to an improvement of myocardial perfusion. The calcium-sensitizing properties seem not to be relevant for cardioprotection by levosimendan at the concentration used.

Functional and antiischaemic effects of the phosphodiesterase inhibitor levosimendan in isolated rabbit hearts.

Several phosphodiesterase inhibitors have been reported to possess antiischaemic properties by improving myocardial oxygen demand/supply balance. Levosimendan is a new phosphodiesterase inhibitor with calcium-sensitizing properties. We investigated the functional and antiischaemic properties of levosimendan in isolated electrically-driven rabbit hearts (Langendorff, constant perfusion pressure: 70 cm H2O, Tyrode solution, Ca++ 1.8 mmol/l, 37 degrees, 200 beats/min.). Acute regional myocardial ischaemia was induced by ligature of a circumflex artery branch and quantified from epicardial NADH-fluorescence photography. The left ventricular pressure was similarly enhanced by levosimendan 10(-7) M or 5 x 10(-6) M (+15%) (P < 0.05). The global coronary flow was increased more markedly by levosimendan 5 x 10(-6) M (+35-50%) compared to 10(-7) M (+25%) (P < 0.05). The relative coronary flow (= global coronary flow/pressure-rate-product) was significantly enhanced only by levosimendan 5 x 10(-6) M (+20-35%) (P < 0.05), but not by levosimendan 10(-7) M (+10-15%) (P > 0.05). Epicardial NADH-fluorescence area and intensity were significantly diminished by levosimendan (-20%) (P < 0.05), and there was no significant difference between myocardial ischaemia reduction by levosimendan 10(-7) M and 5 x 10(-6) M (P > 0.05). Levosimendan is an inotrope with coronary dilator activity, showing antiischaemic effects in isolated rabbit hearts. These may be caused by (1) phosphodiesterase-inhibition and improvement of myocardial perfusion and/or (2) by oxygen-sparing effects, related to calcium sensitization of myofilaments, particularly at lower concentrations associated with a lower coronary dilator activity.

Evidence for norepinephrine cardiotoxicity mediated by superoxide anion radicals in isolated rabbit hearts.

Catecholamines have been demonstrated to be cardiotoxic. Besides hemodynamic alterations, oxygen free radicals generated by the auto-oxidation of catecholamines might contribute to their deleterious effects. We examined the influence of exogenous norepinephrine (NE), after inhibiting functional alterations by alpha and beta-adrenoceptor blockade, on acute regional ischemia (MI). We used isolated electrically-driven rabbit hearts with depleted catecholamine stores (reserpine 7.0 mg/kg i.p. 16-24 h before preparation, Langendorff, constant pressure: 70 cm H2O, Tyrode solution, Ca2+ 1.8 mmol/l, 37 degrees C, 185-200 beats/min). Repetitive MI, separated by a reperfusion period of 50 min, was induced by coronary artery branch ligature and quantitated from epicardial NADH-fluorescence photography. Starting after a reperfusion period of 20 min, isolated hearts were treated with NE (10(-6) M), in the presence of propranolol (10(-6) M), phentolamine (10(-6) M) and vitamin C (3 x 10(-8) M) in the perfusion buffer to prevent the functional effects of NE. The influence of the free radical scavenger superoxide dismutase (SOD) (30 U/ml) or captopril (10(-6) M) on MI was also examined. Left ventricular pressure or coronary flow were not significantly affected by either treatment (p > 0.05). Epicardial NADH-fluorescence area and intensity were, however, significantly enhanced by NE (+22%) (P < 0.05), although propranolol, phentolamine and vitamin C had no significant influence on MI (P > 0.05). SOD had no significant effect on MI in control hearts (P > 0.05) but completely prevented MI enlargement by NE (P > 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Free radical scavenging properties of ?-adrenoceptor blockers are not relevant for cardioprotection in isolated rabbit hearts

Several beta-adrenoceptor-blocking agents have been shown to possess free radical scavenging properties. Therefore, the direct cardioprotective properties of propranolol or pindolol were investigated in comparison to superoxide dismutase (SOD). We used isolated rabbit hearts paced at a constant rate (Langendorff, constant pressure: 70 cm H2O, Tyrode solution, Ca2+ 1.8 mmol/l). Acute regional myocardial ischemia (MI) was induced by left coronary artery branch occlusion and quantitated from epicardial NADH-fluorescence photography. Propranolol (10(-8) mol/l), pindolol (10(-6) mol/l) or SOD (48 I.U./ml) had no significant influence on left ventricular pressure, pressure-rate product or global coronary flow (p > 0.05). Whereas epicardial NADH-fluorescence area after repetitive coronary occlusions was significantly diminished by SOD-treatment (-25%) (p < 0.05), MI size was not significantly affected by either propranolol or pindolol (p > 0.05). Oxygen-derived free radicals contribute to tissue injury during myocardial ischemia, and propranolol or pindolol do not possess free radical scavenging properties relevant for cardioprotection in a repetitive coronary occlusion model in isolated rabbit hearts.

Subepicardial Microischemia Formation Induced by Epicardial Application of Endothelin-1

The effects of endothelin-1 (ET-1), applied topically on the epicardium, on the coronary microcirculation of the beating canine heart were investigated in situ. ET-1 (1, 10, 100, and 1,000 pmol) induced a dose-dependent elevation of the ST segment in the epicardial ECG (n = 5). After application of ET-1 (100 pmol), the beating hearts were rapidly cross-sectioned and freeze-clamped in 120 ms using a specially developed device (n = 6). By NADH fluorescence photography of the cross-sectioned frozen sample, an increased fluorescent area in the subepicardium was clearly observable. The fluorescent dye injected from the left atrium was negative in the NADH fluorescent area. It can be concluded that ET-1, when administered extravascularly, induces severe vasoconstriction and myocardial ischemia in the microcirculation of the beating canine heart.

The exacerbation effect of FeCl3 -ADP on myocardical ischemia as evidenced by computer-assisted image analysis of epicardial NADH-fluorescence photography

The Fe K-edge X-ray absorption near-edge structure (XANES) spectra of two irreversible human hemichromes, spontaneously formed from HbA and HbMetSO (a hemoglobin derivative, where MetD6(55)β has been previously oxidized to sulfoxide by chloramine T) were determined. The results show that the hemichrome from HbMetSO is characterized by the distal histidyl imidazole moved within the bonding distance of the heme iron. Such structure is different from that of the hemichrome spontaneously produced from native human hemoglobin, which probably has a hydroxide group as sixth heme ligand.

Cardiac ischemia and endothelial function in the isolated rabbit heart

Truly effective prevention of reperfusion myocardial damage is precluded in part by a lack of understanding of the earliest events which accompany ischemia. The purpose of this study was to assess the coronary endothelial response to two forms of ischemic injury in an isolated crystalloid perfused rabbit heart. Global cardiac ischemia, confirmed by NADH fluorescence photography, was induced either by mechanically reducing coronary flow by 90% (MRCF, N = 11) or by an infusion of N-formyl-methionyl-leucyl-phenylalanine (fMLP, N = 11), a known stimulus for leukotriene synthesis and coronary vasospasm. Compared with control, MRCF resulted in an increase in effluent concentrations of both prostacyclin (152 ± 22 pg/ml vs 951 ± 214 pg/ml, P < 0.05) and plasminogen activator (0.8 ± .3 IU/ml vs 1.4 ± 0.5, P < 0.05) but no detectable increase in effluent thromboxane B 2 or leukotriene C 4 concentrations. fMLP infusion resulted in an immediate reduction in coronary flow coincident with diffuse myocardial ischemia. In contrast to MRCF, however, fMLP-induced ischemia resulted in a significant but smaller increase in effluent prostacyclin concentration (210 ± 47 pg/ml vs 606 ± .55 pg/ml, P = 0.05) and a marked increase in both thromboxane B 2 (⩽33 ± 4 pg/ml vs 1141 ± 375 pg/ml, P < 0.05) and leukotriene C 4 (<0.25 ng/ml vs 3.3 ± 1.2 ng/ml, P < 0.05) concentrations. Additionally, fMLP caused a reduction in effluent plasminogen activator activity (0.5 ± 0.1 IU/ml vs 0.39 ± 0.1 IU/ml, N = 4). We conclude that endothelial response to ischemia varies not only with the magnitude of but also the nature of the initiating stimulus. Thus a truly specific intervention to prevent postischemic reperfusion injury is likely to require therapy tailored to the initiating ischemic stimulus.

A rapid cross-sectioning and freeze-clamping device for the beating canine heart

A new sampling method of cross-sectioning the canine heart in situ was developed. A mechanical device, driven by spring power, enabled cross-sectioning of a short-axis plane of the beating canine heart (4 mm thick) with high speed rotating blades, at a pre-determined phase of the cardiac cycle, and instantaneous freeze-clamping (2.4 mm thick) with pre-cooled aluminum blocks, all within 120 ms. By this method, the anatomical structures of the sample were well preserved. Transmural metabolism and flow distribution were instantaneously fixed and high resolution of the two-dimensional redox state was obtained by application of NADH fluorescence photography. Micro-samplings from the desired portion of the cross-sectional slice were possible at −190°C. NADH fluorescence of the samples did not increase from the surface to 1.2 mm in depth, confirming that there was no ischemic artifact. With the present technique, a heart sample in which transmural metabolism, and the redox state, are fixed and visualized is attainable, thus providing a new tool for the study of myocardial ischemia.

Transmural anoxic wave front and regional dysfunction during early ischemia.

The relative time courses of early changes in myocardial metabolism and function during anoxia, global ischemia, and regional ischemia were compared in isolated rat hearts. Transmural anoxic wave front was determined with NADH fluorescence photography, and oxygen saturation of myoglobin and dynamic systolic wall thickening were measured with spectrophotometry of light transmitted through the left ventricular free wall. In all three treatments, anoxic wave front first appeared in the subendocardium and reached the epicardial half of the myocardium in 10 s, when oxygen saturation of myoglobin decreased by 50% and tissue ATP and creatine phosphate remained at aerobic levels. During this period, systolic wall thickening decreased gradually in anoxia and global ischemia, whereas a marked decrease in systolic wall thickening and appearance of dyskinesia (wall thinning) occurred in regional ischemia. Thus the early extension of anoxic wave front and metabolic changes are similar with all three treatments, and dyskinesia, observed only in case of regional ischemia, occurs when the inner half is ischemic or anoxic.

Coronary venous perfusion of the ischemic myocardium during acute coronary artery occlusion in isolated rat hearts.

Effects of retrograde coronary venous perfusion on oxygen supply and energy metabolism of ischemic myocardium of the isolated perfused rat heart were examined by means of NADH fluorescence photography. Occlusion of the left coronary artery produced regional ischemia of the left ventricular free wall, as evidenced by the sharply demarcated increase in NADH fluorescence. During ischemia, a narrow area of minimal fluorescence (140 +/- 10 microns), indicating sufficient oxygenation for oxidative phosphorylation, was observed around the epicardial coronary veins in the ischemic lesion. Retrograde perfusion was introduced through the coronary vein (left cardiac vein) that drained off the ischemic area, which resulted in a marked reduction of the area of increased NADH fluorescence in the epicardial surface. In the cross-sectional view, although the myocardium of the entire ischemic area induced by left coronary artery occlusion could be perfused by venous retroperfusion, the effect on reduction of the area of increased NADH fluorescence was seen only in the epicardial half of the myocardium. Retrograde coronary venous perfusion also resulted in a small increase in tension development (P less than 0.05), a decrease in resting tension (P less than 0.01), and partial preservation of myocardial high energy phosphate content (P less than 0.01). We propose that coronary venous retroperfusion improves oxygenation, partially preserves oxidative phosphorylation in the epicardium, and improves contractile function in the ischemic region.

Topographic analysis of the redox state of rat brain by NADH fluorescence photography of cross sections.

Two-dimensional changes of the redox level of NADH were measured by fluorescence photography with the aid of computer-processing in cross sections of rat brain that had been frozen in situ in liquid nitrogen. Structure-related heterogeneity was noted in the distribution of the redox level in normal brain of conscious rats. Using 2-deoxy-[14C]glucose autoradiography, the area showing relatively high NADH fluorescence was found to be the area of high glucose utilization. Quantitatively, however, the fluorescence intensity did not parallel the rate of glucose uptake. Increase of NADH fluorescence was observed specifically in the nucleus caudatus putamen and the thalamus when the rats were anesthetized with pentobarbital. Chemical determination of the NADH content was also performed simultaneously, and the results were consistent with those obtained by fluorescence photography.

Progression of myocardial ischemia from endocardium to epicardium after coronary occlusion assessed by NADH fluorescence photography: Y. Taira, H. Kanaide, M. Nakamura. Research Institute of Angiocardiology and Cardiovascular Clinic, Kyushu University Medical School, Fukuoka, Japan

Progression of myocardial ischemia from endocardium to epicardium after coronary occlusion assessed by NADH fluorescence photography: Y. Taira, H. Kanaide, M. Nakamura. Research Institute of Angiocardiology and Cardiovascular Clinic, Kyushu University Medical School, Fukuoka, Japan

Decrease in acute myocardial ischemia by hyaluronidase in isolated, perfused, rabbit hearts

Hyaluronidase has been reported to reduce infarct size and cellular damage after coronary artery occlusion. The influence of hyaluronidase (H) on experimental myocardial ischemia was studied in isolated perfused rabbit hearts. Changes in ischemic area were assessed by epicardial NADH fluorescence photography, an intrinsic, high-resolution display of myocardial ischemia. Computerized determination of ischemic area was made from standardized photographs. H was begun 5 min after coronary artery ligation at 4 units/ml perfusate. NADH fluorophotographs were taken at 10-min intervals up to 40 min of ischemia. Coronary sinus oxygen tension ( P esO 2) myocardial oxygen consumption (MV̇ O 2) and coronary flow were determined. After 40 min, the hearts were perfused with a rhodamine solution to indicate areas of myocardial perfusion. In 18 H-treated hearts 55 ± 6% (mean ± SE) of the nonperfused area was ischemic (NADH fluorescent) and the ischemic areas had a patchy distribution. In 26 untreated hearts 86 ± 2% of the nonperfused area was ischemic and the ischemic areas were uniform, ( P < 0.001). The distance between perfused and ischemic tissue was 861 ± 76 μm in the H-treated and 359 ± 19 μm in the untreated hearts, ( P < 0.001). In the H-treated hearts P esO 2 increased to 154% of the postligation control while it decresed to 77% in the untreated hearts ( P < 0.001). MV̇ O 2 decreased to 87% of control after ligation in both groups. The H-treated hearts had a further decline of 37% while the untreated hearts had no further change. In the H-treated hearts, coronary flow increased to 150% of the postligation control while it fell to 80% in the untreated group ( P < 0.001). We conclude that hyaluronidase increases P esO 2 and coronary flow while it decreases MV̇ O 2 during acute ischemia. In hyaluronidase-treated hearts, significant amounts of myocardium remain normoxic within the nonperfused areas.