Tetsuo Ohkuwa

Hydroxyl radical formation in diabetic rats induced by streptozotocin

Production of hydroxyl radicals was examined in the diabetic rats induced by streptozotocin to prove its involvement to the pathogenesis of diabetes. Hydroxyl radicals generated in plasma, heart muscle, liver and brain of the hyperglycemic rats were quantitatively assayed by trapping hydroxyl radicals with salicylic acid as 2,3- and 2,5-dihydroxybenzoic acid. The concentrations of 2,3- and 2,5-dihydroxybenzoic acid were significantly increased in all the tissues of the diabetic rats. In the brain and heart muscle of the diabetic rats, the increase of 2,3-dihydroxybenzoic acid was more manifest than that of 2,5-dihydroxybenzoic acid, while in liver 2,5-dihydroxybenzoic acid increased markedly. All the values of 2,3-dihydroxybenzoic acid detected in the tissues of the diabetic rats were quite higher than those in control. Hydroxyl radical production and blood glucose concentration were depended almost linearly on the amount of streptozotocin injected to rats up to 60 mg/kg body weight. It was suggested that 2,3-dihydroxybenzoic acid was produced from hydroxyl radicals themselves, while 2,5-dihydroxybenzoic acid was produced by hydroxylation of salicylic acid not only with hydroxyl radicals, but also by enzymatic reaction of microsomal cytochrome-P450. Hydroxyl radical formation may account for some pathological process especially in the heart muscle and brain.

Blood lactate and glycerol after 400-m and 3,000-m runs in sprint and long distance runners

SummaryLactate, glycerol, and catecholamine in the venous blood after 400-m and 3,000-m runs were determined in eight sprint runners, eight long distance runners, and seven untrained students. In 400-m sprinting, average values of velocity, peak blood lactate, and adrenaline were significantly higher in the sprint group than in the long distance and untrained groups. The mean velocity of 400-m sprinting was significantly correlated with peak blood lactate in the untrained (r=0.76,P<0.05) and long distance (r=0.71,P<0.05) groups, but not in the sprint group. In the 3,000-m run, on the other hand, average values of velocity and glycerol were significantly higher in the long distance group than in the sprint and untrained groups, but there are no significant differences in lactate levels between the three groups. These results suggest that 1) performance in 400-m sprinting may depend mainly upon an energy supply from glycolysis in the long distance and untrained group, but in the sprinters is influenced not only by glycolysis, but also by other factors such as content of ATP or force per unit muscle cross-sectional area; 2) peak blood lactate obtained after 400-m sprinting may be used as a useful indication of anaerobic work capacity in the long distance and untrained groups, but not in the sprinters. 3) high speed in the 3,000-m run could be maintained in the long distance runners by means of a greater energy supply from lipid metabolism as compared with sprinters or untrained subjects.

Effects of Pre-exercise Listening to Slow and Fast Rhythm Music on Supramaximal Cycle Performance and Selected Metabolic Variables

We examined the effect of listening to two different types of music (with slow and fast rhythm), prior to supramaximal cycle exercise, on performance, heart rate, the concentration of lactate and ammonia in blood, and the concentration of catecholamines in plasma. Six male students participated in this study. After listening to slow rhythm or fast rhythm music for 20 min, the subjects performed supramaximal exercise for 45 s using a cycle ergometer. Listening to slow and fast rhythm music prior to supramaximal exercise did not significantly affect the mean power output. The plasma norepinephrine concentration immediately before the end of listening to slow rhythm music was significantly lower than before listening (p < 0.05). The plasma epinephrine concentration immediately before the end of listening to fast rhythm music was significantly higher than before listening (p < 0.05). The type of music had no effect on blood lactate and ammonia levels or on plasma catecholamine levels following exercise. In conclusion, listening to slow rhythm music decreases the plasma norepinephrine level, and listening to fast rhythm music increases the plasma epinephrine level. The type of music has no impact on power output during exercise.

Peak blood lactate after short periods of maximal treadmill running

SummaryBlood lactate was determined in 19 untrained subjects after maximal treadmill exercise lasting for about 1 min. It was found that blood lactate increases after exercise, reaching a maximum level 6–9 min after the cessation of exercise, and the average time for the appearance of the peak blood lactate concentration was 7.65 min. Peak blood lactate concentration at 7.65 min (CLA7.65), which was calculated by substituting t (7.65) into the equation for the lactate recovery curve for each subject, agreed well with the observed peak blood lactate concentration (r=0.98, p<0.001). In addition, correlations of r=−0.65, r=−0.78, r=−0.79 were found between CLA7.65 and the running times of 100 m, 200 m, and 400 m sprints, respectively. These results suggest that CLA7.65 may be used as a valid indicator of anaerobic work capacity in man.

Effect of gender differences and voluntary exercise on antioxidant capacity in rats

The effects of gender difference and voluntary exercise on antioxidant capacity in rats were evaluated. The subjects were divided into two groups, physically active and sedentary. In the sedentary group, the level of hydroxyl radical in the liver was higher (P<0.001) in male rats than in female rats, however, in the physically active group, the level in male rats was lower (P<0.05) than in female rats. The levels of reduced glutathione (GSH) in physically active males and females were higher compared to those in the sedentary group. The physically active group also showed an increase in antioxidant enzymes, such as glutathione peroxidase (GPx), glutathione reductase (GR) and superoxide dismutase activities. The level of liver GSH was higher in physically active females than in physically active males. For both groups, GPx and GR activities in females were significantly higher than in males. These results indicate that female rats have an intrinsically higher antioxidant capacity, which resulted in increased levels of GSH via the glutathione redox cycle and gamma-glutamyl cycle enzymes. The adaptation to altered antioxidant capacity, induced by physical activity, appeared to be affected by gender differences.

Salivary and blood lactate after supramaximal exercise in sprinters and long‐distance runners

This investigation examined the reproducibility of salivary lactate measurement in long‐distance runners following a 3000‐m run and compared the salivary and blood lactate concentrations in sprinters and long‐distance runners following a 400‐m run. There was no significant difference in salivary and blood lactate between the first and second 3000‐m run test. The peak salivary and blood lactate following a 400‐m run was higher in sprinters than in long‐distance runners. There was a significant relationship between the peak lactate of saliva and that of blood following a 400‐m run. The results showed that the salivary lactate following exercise was reproducible and the salivary lactate concentration may serve as a relevant indicator in determining which have a higher lactate production.

Peak blood ammonia and lactate after submaximal, maximal and supramaximal exercise in sprinters and long-distance runners

SummaryThe purpose of this study was to elucidate the difference in peak blood ammonia concentration between sprinters and long-distance runners in submaximal, maximal and supramaximal exercise. Five sprinters and six long-distance runners performed cycle ergometer exercise at 50% maximal, 75% maximal, maximal and supramaximal heart rates. Blood ammonia and lactate were measured at 2.5, 5, 7.5, 10 and 12.5 min after each exercise. Peak blood ammonia concentration at an exercise intensity producing 50% maximal heart rate was found to be significantly higher compared to the basal level in sprinters (P < 0.01) and in long-distance runners (P < 0.01). The peak blood ammonia concentration of sprinters was greater in supramaximal exercise than in maximal exercise (P < 0.05), while there was no significant difference in long-distance runners. The peak blood ammonia content after supramaximal exercise was higher in sprinters compared with long-distance runners (P < 0.01). There was a significant relationship between peak blood ammonia and lactate after exercise in sprinters and in long-distance runners. These results suggest that peak blood ammonia concentration after supramaximal exercise may be increased by the recruitment of fast-twitch muscle fibres and/or by anaerobic training, and that the processes of blood ammonia and lactate production during exercise may be strongly linked in sprinters and long-distance runners.

Plasma LDH and CK activities after 400 m sprinting by well-trained sprint runners

SummaryBlood lactate concentration and the activities of plasma LDH and CK were determined in 13 well-trained middle distance runners after a 400-m sprint. It was found that there is a significant relationship between mean velocity in the 400-m sprint and plasma CK activity (r=−0.56,P<0.05), but the mean sprint velocity did not correlate with peak blood lactate concentration (r=−0.09) or plasma LDH activity (r=−0.40). There was a significant negative correlation between mean sprint velocity and H type LDH isozyme activity (r=−0.66,P<0.05), and a significant positive correlation with M type LDH isozyme activity (r=0.66,P<0.05). These results suggest that the magnitude of enzyme efflux from tissue into blood may be depressed by training, and that in well-trained sprinters plasma CK and LDH isozyme activities may be better indicators of physical training and/or physical performance than peak blood lactate or plasma LDH activities.

Ammonia and lactate in the blood after short-term sprint exercise

SummaryNine well-trained subjects performed 15-, 30-and 45-s bouts of sprint exercise using a cycle ergometer. There was a significant difference in the mean power between a 15-s sprint (706.0 W, SD 32.5) and a 30-s sprint (627.0 W, SD 27.8;P<0.01). The mean power of the 30-s sprint was higher than that of the 45-s sprint (554.7 W, SD 29.8;P<0.01). Blood ammonia and lactate were measured at rest, immediately after warming-up, and 2.5, 5, 7.5, 10, 12.5 min after each sprint. The peak blood ammonia content was 133.8 μmol·1−1, SD 33.5,- for the 15-s sprint, 130.2 μol·1−1, SD 44.9, for the 30-s sprint, and 120.8 μmol ·1−1, SD 24.6, for the 45-s sprint. Peak blood lactates after the 15-, 30- and 45-s sprints were 8.1 mmol · 1−1, SD 1.7, 11.2 mmol · 1−1, SD 2.4, and 14.7 mmol ·1−1, SD 2.1, respectively. There was a significant linear relationship between peak blood ammonia and lactate in the 15-s (r, 0.709;P< 0.05), 30-s (r, 0.797;P<0.05) and 45-s (r, 0.696;P<0.05) sprints. Though the peak blood lactate content increased significantly with increasing duration of the sprints (P<0.01), no significant difference was found in peak blood ammonia content among the 15-, 30- and 45-s sprints. These results suggest that the peak value of ammonia in the blood appears in sprints within 15-s and that the blood ammonia level is linked to the lactate in the blood.

Ventilatory response to hypercapnia in sprint and long-distance swimmers

SummaryVentilatory response lines to carbon dioxide at rest were determined by the rebreathing method in 10 untrained subjects, 17 sprint swimmers, and 11 long-distance swimmers. It was found that the mean slope of the ventilatory response line of the swimmer was lower than that of the untrained group, and the mean slope of the long distance swimmer was lower as compared with the sprint swimmer, though these differences were statistically not significant. The differences in the hypercapnic drive between untrained subjects and swimmers obtained here is discussed in connection with their maximum oxygen uptake.