Adaptive changes in coenzyme Q biosynthesis to myocardial reperfusion in young and aged rats.

This study investigated the biosynthesis of ubiquinone in isolated and perfused hearts of young and aged rats exposed to ischemia and reperfusion. A first group of hearts was used to determine the changes in coenzyme Q9 (CoQ9) and coenzyme Q10 (CoQ10) concentrations at mitochondrial and microsomal level after 30 min of ischemia (98% reduction of the preischemic flow) and 60 min of reperfusion. A second group was utilized to evaluate the rate of CoQ9 and CoQ10 biosynthesis in the membranes by dissolving two ubiquinone precursors, p-OH-[U-14C]benzoate and mevalonolactone, in the perfusion buffer. The hearts were aerobically perfused for 60 min in the presence of the precursors either immediately after the equilibration period or following 30 min ischemia. The young rat hearts showed a 30% reduction in the mitochondrial levels of CoQ9 after ischemia and reperfusion with respect to the preischemic values (P < 0.05 and P < 0.01, respectively). On the contrary, the mitochondrial CoQ9 content was not modified under these conditions in the aged hearts. At the end of reperfusion, the biosynthesis of mitochondrial CoQ9 and CoQ10 was higher in the young rats (P < 0.05), and lower in the aged rats (P < 0.05), with respect to the aerobic perfusion. In both young and aged rats minor changes in CoQ9 concentrations and biosynthesis were observed at microsomal level. These results indicate that myocardial reperfusion decreases the mitochondrial content of ubiquinone and stimulates CoQ9 biosynthesis in young rats but not in aged rats.

[Coenzyme Q9 biosynthesis in the aging myocardium after ischemia and reperfusion]. / Biosintesi di coenzima Q9 nel miocardio senescente dopo ischemia e riperfusione.

The purpose of the present study was to evaluate the biosynthesis of coenzyme Q9 (CoQ9) in isolated and perfused young (6 months) and aged (24 months) rat hearts, either under aerobic perfusion condition or during postischemic reperfusion. The young and aged hearts have been divided into 2 groups: Group A, aerobic perfusion for 60 min with recirculating Krebs-Henseleit solution, containing 0.8 microM p-OH-[U-14C]benzoate plus 2.5 mM mevalonlactone; Group B, severe ischemic perfusion for 30 min, followed by 60 min of reperfusion under the same experimental condition of Group A. At the end of the reperfusion the mitochondrial content of CoQ9 was lower in young than aged rat hearts (p < 0.01). In Group A the incorporation of the labeled precursor into mitochondrial CoQ9 was greater in the hearts of aged than young rats (p < 0.01); on the contrary, in Group B this incorporation was significantly reduced in aged than in young rats (p < 0.05). Thus, it is possible that, in the aged rat heart, the higher activity of CoQ9 biosynthesis is related to an elevated turnover of the coenzyme due to the aging process; moreover, this activity is partially reduced by an ischemic-reperfusion stress.

Changes in myocardial mitochondrial respiration after ligation of the coronary artery in pigs.

After ligation of the left coronary artery, porcine cardiac mitochondria were isolated by homogenizing the tissue and treating the myofibrillar pellet with nagarse. When compared with unligated controls, the ischemic myocardium showed decreases in phosphocreatine (to 41%), ATP (to 56%) and in the mitochondrial respiratory control index (to 69% and 78% as measured with glutamate and succinate respectively). No changes were found in the corresponding P/O ratios. Similar results were obtained upon separation of the mitochondria into two main fractions by a density gradient technique, though only one of these fractions showed a fall in succinate-supported respiration. The results suggest that ischemia decreases the NADH-dehydrogenase activity of cardiac mitochondria.

Influence of age on oxidative damage in mitochondria of ischemic and reperfused rat hearts.

Hearts from rats aged 3 months and 24 months respectively were isolated and subjected to a brief ischemia. The extent of myocardial injury, measured by release of creatine phosphokinase into coronary effluents and by developed tension, was greater in the young rats than in the old when compared with their corresponding non-ischemic controls. The amount of peroxidation, measured in the isolated mitochondria using the malondialdehyde method, was also greater in the younger rats. In contrast, when mitochondria from non-ischemic hearts were incubated for 20 minutes in a medium containing FeCl3, NADPH and ADP, known to generate hydroxyl radicals, significant peroxidation (together with a decrease in respiratory control indices) was obtained only from mitochondria isolated from the older rats. If, as the in vitro results suggest, the mitochondria of the old rats are not less sensitive to peroxidative attack, the difference between the effects of ischemia in the two age groups may be due to a lower rate of formation of reactive species of oxygen or to a greater anti-oxidative cytosolic capacity in the hearts of older rats. Alternatively, the overall oxidative stress following ischemia may be due to the effects of different radicals which target different parts of the mitochondrial membrane.

Comparison of verapamil versus propranolol therapy in syndrome X.

The effects of oral verapamil, 320 mg daily, propranolol, 120 to 160 mg daily, and placebo were compared in 16 patients presenting with transient myocardial ischemia without evidence of coronary atherosclerosis or vasospasm on angiography (syndrome X). Testing was done according to a randomized double-blind crossover placebo-controlled trial consisting of 3 consecutive 7-day treatment periods with verapamil or propranolol or placebo. Patients underwent continuous 48-hour electrocardiographic monitoring before therapy (run-in phase) and during the last 2 days of each treatment period. A total of 391 episodes of diagnostic (greater than or equal to 0.15 mV) ST depression was recorded during the trial. Of these, 23 were symptomatic. None of the episodes occurred while the patients were asleep, 25% during exercise, 35% during minimal physical activity and 40% at rest. Rest included activities demanding mental arousal (conversation, reading or watching television). Heart rate at the onset of ST depression was higher (greater than or equal to 10 beats/min) than that observed in the 5 minutes preceding ischemia in 95% of the episodes. In the group as a whole, the average number of ischemic episodes per 24 hours was significantly reduced during propranolol therapy compared with placebo (0.7 +/- 0.6 vs 3.9 +/- 1.8; p less than 0.0005). No significant differences were seen during verapamil treatment (3.4 +/- 1.7 vs 3.9 +/- 1.8). It is concluded that transient myocardial ischemia in syndrome X is mostly precipitated by an increase in oxygen consumption, presumably due to a heightened sympathetic activity. Accordingly, beta blockers may represent the first line of treatment.

[Prediction of the infarct size by the serum levels of creatin kinase. A new methodological method (author's transl)]. / La previsione dell'area infartuata dai livelli sierici di creatinchinasi. Nuova proposta metodologica.

Logistic equation is proposed as a new mathematical model describing the course of the ascending branch of the serum creatine kinase curve: E(t) = K divided by 1 + ea-bt where: E(t) = CK concentration at time t (mU/ml); t = time in hours from the onset of enzyme release; e = natural logarithm base; K = horizontal asymptote of the curve (maximal enzyme activity); a, b = typical variable prameters of the curve. Prediction is based on the identification of the infection point of the ascending branch of the serum CK curve. The enzyme activity corresponding to this point is half of the maximal one. In 14 patients with acute myocardial infarction infarct size (CK-g-Eq) was calculated by the method of Shell et al. In these patients the average differences between observed and predicted parameters were respectively (X +/- SD): -0.64 +/- 2.13 h for the maximal activity time; 16.57 +/- 53.15 mU/ml for the maximal activity and 0.02 +/- 2.44 CK-g-Eq for the infarct size. In detail it can be observed that the average of the per cent differences between observed and predicted infarct size was 1.10 +/- 5.31% and the maximal per cent difference only +10.40%.

[A Study of the enzymes of the alkaline phosphatase in commercial sera (author's transl)]. / Studio degli enzimi della fosfatasi alcalina nei sieri di riferimento del commercio.

We have examined alkaline phosphatase in five commercial sera employing three analyzers. Alkaline phosphatase in three samples is underestimated or overestimated according to the analyzers used. Therefore we have studied the isoenzymatic fractions employing the fractionation of alkaline phosphatase on celluloseacetate. Alkaline phosphatase isoenzymes have physical and biochemical marks different from human sera. In human sera on the contrary have not noticed any difference according to the analyser used.