Seven days of oral taurine supplementation does not increase muscle taurine content or alter substrate metabolism during prolonged exercise in humans

This study examined 1) the plasma taurine response to acute oral taurine supplementation (T), and 2) the effects of 7 days of T on muscle amino acid content and substrate metabolism during 2 h of cycling at approximately 60% peak oxygen consumption (VO2peak). In the first part of the study, after an overnight fast, 7 volunteers (28+/-3 yr, 184+/-2 cm, 88.0+/-6.6 kg) ingested 1.66 g oral taurine doses with breakfast (8 AM) and lunch (12 noon), and blood samples were taken throughout the day. In the second part of the study, eight men (22+/-1 yr, 181+/-1 cm, 80.9+/-3.8 kg, 4.21+/-0.16 l/min VO2peak) cycled for 2 h after 7 days of placebo (P) ingestion (6 g glucose/day) and again following 7 days of T (5 g/day). In the first part of the study, plasma taurine was 64+/-4 microM before T and rose rapidly to 778+/-139 microM by 10 AM and remained elevated at noon (359+/-56 microM). Plasma taurine reached 973+/-181 microM at 1 PM and was 161+/-31 microM at 4 PM. In the second part of the study, seven days of T had no effect on muscle taurine content (mmol/kg dry muscle) at rest (P, 44+/-15 vs. T, 42+/-15) or after exercise (P, 43+/-12 vs. T, 43+/-11). There was no difference in muscle glycogen or other muscle metabolites between conditions, but there were notable interaction effects for muscle valine, isoleucine, leucine, cystine, glutamate, alanine, and arginine amino acid content following exercise after T. These data indicate that 1) acute T produces a 13-fold increase in plasma taurine concentration; 2) despite the ability to significantly elevate plasma taurine for extended periods throughout the day, 7 days of T does not alter skeletal muscle taurine content or carbohydrate and fat oxidation during exercise; and 3) T appears to have some impact on muscle amino acid response to exercise.     

Rapid analysis of taurine in energy drinks using amino acid analyzer and Fourier transform infrared (FTIR) spectroscopy as basis for toxicological evaluation

Summary. So-called energy drinks with very high amounts of taurine (up to 4000 mg/l are usually granted by certificates of exemption) are increasingly offered on the market. To control the currently valid maximum limits of taurine in energy drinks, a simple and rapid analytical method is required to use it routinely in food monitoring. In this article, we describe a fast and efficient analytical method (FTIR-spectroscopy) that is able to reliably characterize and quantify taurine in energy drinks. The determination of taurine in energy drinks by FTIR was compared with amino acid analyzer (ion chromatography with ninhydrin-postcolumn derivatization). During analysis of 80 energy drinks, a median concentration of 3180 mg/l was found in alcohol-free products, 314 mg/l in energy drinks with spirits, 151 mg/l in beer-containing drinks and 305 mg/l in beverages with wine. Risk analysis of these products is difficult due to the lack of valid toxicological information about taurine and its interferences with other ingredients of energy drinks (for example caffeine and alcohol). So far, the high taurine concentrations of energy drinks in comparison to the rest of the diet are scientifically doubtful, as the advertised physiological effects and the value of supplemented taurine are unproven.     

Co-variation of plasma sodium,taurine and other amino acid levels in critical illness

Summary.  This study investigates the relationship between changes in plasma sodium and changes in amino acid levels in a patient with post-traumatic sepsis and prolonged critical illness. Ninety-two consecutive measurements were performed at regular intervals over a period of many weeks; these consisted in the determination of full amino-acidograms, plasma sodium and complementary variables. A unique, highly significant inverse correlation between taurine and plasma sodium was found (r² = 0.48, p < 0.001). All other amino acids were unrelated, or much more weakly related, to sodium. Taurine was also strongly and directly related to phosphoethanolamine, glutamate and aspartate. Changes in sodium and in levels of these amino acids explained up to 86% of the variability of taurine. Besides, levels of these amino acids maintained a high degree of co-variation, remaining reciprocally related one to each other, directly, with r² ranging between 0.33 and 0.59 (p < 0.001 for all). There were similar findings for β-alanine, which however was measured inconsistently. These data provide gross clinical evidence of a specific link binding plasma sodium and taurine levels, and may be consistent with occurrence of opposite and interdependent shifts of sodium and taurine between intravascular and extravascular space, to maintain osmoregulation. Co-variation of taurine with the other amino acids may be related to the same phenomenon, and/or to similarities in transport systems and chemical structure, or true metabolic interactions. Received April 16, 2002 Accepted June 19, 2002 Published online November 14, 2002 RID="*" ID="*"  Presented at the 7^th International Congress on Amino Acids and Proteins, Vienna (Austria), August 6–10, 2001. Acknowledgements The authors acknowledge the kind assistance of Mr. Maurizio Cianfanelli, from the Catholic University School of Medicine, Rome, Italy. Authors' address: Dr. Carlo Chiarla, Via Augusto Tebaldi, 19, I-00168 Roma, Italy, E-mail: carlo.chiarla@rm.unicatt.it     

The relationship between plasma potassium concentration and muscle torque during recovery following intense exercise

The present study investigated the relationship between plasma potassium ion concentration ([K⁺]) and skeletal muscle torque during three different 15-min recovery periods after fatigue induced by four 30-s sprints. Four males and one female completed the multiple sprint exercise on three separate days; recovery was passive, i.e. no cycling exercise (PRec), active cycling at 30% peak oxygen consumption O_2peak (30% Rec) and active cycling at 60% O_2peak (60% Rec). Plasma [K⁺] was measured from blood sampled from an antecubital vein of subjects at rest and at 0, 3, 5, 10 and 15 min into each recovery. Isokinetic leg strength was measured at rest and at 1, 6, 11 and 16 min during each recovery. Following the exhaustive sprints, [K⁺] increased significantly from an average mean (SEM) resting value of 3.81 (0.07) mmol · l⁻¹ to 4.48 (0.19) mmol · l⁻¹ (P < 0.01). In all recovery conditions, plasma [K⁺] returned to resting levels within 3 min following the fourth sprint. However, in the two active recovery conditions plasma [K⁺] increased over the remainder of the recovery periods to 4.36 (0.12) mmol · l⁻¹ in the 30% Rec condition and 4.62 (0.12) mmol · l⁻¹ in the 60% Rec condition, the latter being significantly higher than the former (P < 0.01). The maximum torque measured following the sprints decreased significantly, on average, to 61.1 (8.36)% of peak levels (P < 0.01). After 15 min of recovery, maximum torque was highest in the 30% Rec condition at 92.13 (3.06)% of peak levels (P < 0.01), compared to 85.23 (3.64)% and 85.71 (0.82)% for the PRec and 60% Rec conditions, respectively. In contrast to the significant differences in plasma [K⁺] across all three recovery conditions, muscle torque recovery was significantly different in only the 30% Rec condition. In summary, recovery of peak levels of muscle torque following fatiguing exercise does not appear to follow changes in plasma [K⁺]. Accepted: 18 October 1996     

Body fluid homeostasis and cardiovascular adjustments during submaximal exercise: influence of chewing coca leaves

 The present study was undertaken to determine the haematological and cardiovascular status, at rest and during prolonged (1 h) submaximal exercise (approximately 70% of peak oxygen uptake) in a group (n = 12) of chronic coca users after chewing approximately 50 g of coca leaves. The results were compared to those obtained in a group (n = 12) of nonchewers. At rest, coca chewing was accompanied by a significant increase in heart rate [from 60 (SEM 4) TO 76 (SEM 3) beats · min⁻¹], in haematocrit [from 53.2 (SEM 1.2) to 55.6 (SEM 1.1)%] in haemoglobin concentration, and plasma noradrenaline concentration [from 2.8 (SEM 0.4) to 5.0 (SEM 0.5) μmol · l⁻¹]. It was calculated that coca chewing for 1 h resulted in a significant decrease in blood [−4.3 (SEM 2.2)%] and plasma [−8.7 (SEM 1.2)%] volume. During submaximal exercise, coca chewers displayed a significantly higher heart rate and mean arterial blood pressure. The exercise-induced haemoconcentration was blunted in coca chewers compared to nonchewers. It was concluded that the coca-induced fluid shift observed at rest in these coca chewers was not cumulative with that of exercise, and that the hypovolaemia induced by coca chewing at rest compromised circulatory adjustments during exercise. Accepted: 29 October 1996     

Glutamate ingestion and its effects at rest and during exercise in humans.

Glutamate is central to several transamination reactions that affect the production of ammonia, alanine, glutamine, as well as TCA cycle intermediates during exercise. To further study glutamate metabolism, we administered 150 mg/kg body wt of monosodium glutamate (MSG) and placebo to seven male subjects who then either rested or exercised (15-min cycling at approximately 85% maximal oxygen consumption). MSG ingestion resulted in elevated plasma glutamate, aspartate, and taurine, both at rest and during exercise (P < 0.05), whereas most other amino acids were unchanged. Neither plasma alanine nor ammonia was altered at rest. During exercise and after glutamate ingestion, alanine was increased (P < 0.05) and ammonia was attenuated (P < 0.05). Glutamine was also elevated after glutamate ingestion during rest and exercise trials. MSG administration also resulted in elevated insulin levels (P < 0.05), which were parallel to the trend in C-peptide levels. Thus MSG can successfully elevate plasma glutamate, both at rest and during exercise. The plasma amino acid responses suggest that increased glutamate availability during exercise alters its distribution in transamination reactions within active muscle, which results in elevated alanine and decreased ammonia levels.     

Changes in Amino Acids and Nitric Oxide Concentration in Cerebrospinal Fluid During Labor Pain

This study analyzes the relationship between amino acids and pain perception during active labor. Cerebrospinal fluid (CSF) levels of the excitatory amino acids (EAAs)—glutamate, aspartate and their amide forms, inhibitory amino acids (IAAs)—glycine, γ-amino butyric acid (GABA) and taurine and nitric oxide (NO) related compounds—arginine and citrulline (by-product of NO synthesis) were compared between pregnant women at term pregnancy with labor pain (n = 38) and without labor pain (Caesarian section; n = 30). The levels of aspartate, glycine, GABA and citrulline were significantly higher; whilst taurine was significantly lower in the labor pain group. These findings suggest that aspartate and NO are associated with labor pain. An inhibitory role for the IAA taurine and a pronociceptive role for glycine in labor pain are proposed.     

Glutamate ingestion: the plasma and muscle free amino acid pools of resting humans

Monosodium glutamate (MSG) ingestion is known to increase plasma glutamate concentration, and MSG infusion stimulates insulin secretion. We investigated the impact of MSG ingestion on both the plasma and intramuscular amino acid pools. Nine postprandial adults ingested MSG (150 mg/kg) and rested for 105 min. Venous blood was sampled preingestion and then every 15 min; vastus lateralis muscle biopsies were taken preingestion and at 45, 75, and 105 min postingestion. Venous plasma glutamate and aspartate concentrations increased (P 相似文献   

Effects of resistance training and protein plus amino acid supplementation on muscle anabolism,mass, and strength

Summary. This study examined 10 wks of resistance training and the ingestion of supplemental protein and amino acids on muscle performance and markers of muscle anabolism. Nineteen untrained males were randomly assigned to supplement groups containing either 20 g protein (14 g whey and casein protein, 6 g free amino acids) or 20 g dextrose placebo ingested 1 h before and after exercise for a total of 40 g/d. Participants exercised 4 times/wk using 3 sets of 6–8 repetitions at 85–90% of the one repetition maximum. Data were analyzed with two-way ANOVA (p < 0.05). The protein supplement resulted in greater increases in total body mass, fat-free mass, thigh mass, muscle strength, serum IGF-1, IGF-1 mRNA, MHC I and IIa expression, and myofibrillar protein. Ten-wks of resistance training with 20 g protein and amino acids ingested 1 h before and after exercise is more effective than carbohydrate placebo in up-regulating markers of muscle protein synthesis and anabolism along with subsequent improvements in muscle performance.     

A study on the estimation of sulfur-containing amino acid metabolism by the determination of urinary sulfate and taurine

Summary.  Sulfate and taurine are major end products of sulfur-containing amino acid metabolism in mammals including humans, and they are excreted in urine. Average excretions (μmol/mg of creatinine) in the morning urine of 58 female college students were: total (free plus ester) sulfate (a), 12.53 ± 3.85; free sulfate, 11.57 ± 3.69; taurine, 0.78 ± 0.53. Ratio of total sulfate and taurine was 10 : 0.6. Regression lines obtained by plotting total sulfate, free sulfate, or total sulfate plus taurine against urea have shown that the former excretions are significantly correlated with urea excretion. Excretion of total sulfate at zero point of urea excretion (b) was 5.30, which corresponded to 42.3% of average excretion (12.53) and was assumed to be derived from dietary sulfate. The difference 7.23 (a − b) seemed to be derived from sulfur-containing amino acids. It was pointed out that the difference of average sulfate excretion and sulfate excretion at zero urea excretion, namely a − b, was appropriate for the metabolic index of sulfur-containing amino acids of the group examined. As free sulfate constituted 92.3% of total sulfate, excretion of ester sulfate was at a constant level, and that of taurine was not significantly correlated with urea excretion, the value of free sulfate corresponding to the value a − b of total sulfate mentioned above seemed to be a reliable and convenient index in the assessment of sulfur-containing amino acid metabolism. Received December 3, 2001 Accepted January 2, 2002 Published online August 30, 2002 Authors' address: Dr. Toshihiko Ubuka, Department of Clinical Nutrition, Kawasaki University of Medical Welfare, Kurashiki Okayama, 701-0193 Japan, E-mail: ubukatos@mw.kawasaki-m.ac.jp     

Effect of regular training on the myocardial and plasma concentrations of taurine andα-amino acids in thoroughbred horses

Summary Exercise induces significant changes in the free intracellular amino acid pool in skeletal muscle but little is known of whether such changes also occur in cardiac muscle. In this study the effect of regular exercise on the size and the constituents of the free amino acid pool in the hearts and in the plasma of thoroughbred horses was investigated. The total free intracellular amino acid pool in the hearts of control horses was 30.9 ± 1.2mol/g wet weight (n = 6). Glutamine but not taurine was present at the highest concentration (13.5 ± 0.9 and 7.7 ± 0.69mol/g wet weight for glutamine and taurine respectively). As for the rest of the amino acids in the pool, only glutamate and alanine were present at levels greater than 1mol/g wet weight (4.6 ± 0.25 and 1.7 ± 0.14 for glutamate and alanine respectively). The tissue to plasma ratio was highest for taurine at 155, followed by glutamate at 111, aspartate and glutamine at 37, alanine at 5.8 and ratios of less than 3 for the rest of the amino acids. The total free intracellular amino acid pool in the hearts of exercised horses was slightly but not significantly lower than control (28.1 ±1.1mol/g wet weight, n = 6). Regular exercise increased the intracellular concentration of threonine, valine, isoleucine, leucine and phenylalanine but was only significant (p < 0.05) for threonine. This work has documented the profile of taurine and protein amino acids in the heart and in the plasma of thoroughbred horses and showed that in contrast to skeletal muscle, heart muscle does not show major changes in amino acids during regular exercise.     

The deleterious effects of bed rest on human skeletal muscle fibers are exacerbated by hypercortisolemia and ameliorated by dietary supplementation

Prolonged inactivity associated with bed rest in a clinical setting or spaceflight is frequently associated with hypercortisolemia and inadequate caloric intake. Here, we determined the effect of 28 days of bed rest (BR); bed rest plus hypercortisolemia (BRHC); and bed rest plus essential amino acid (AA) and carbohydrate (CHO) supplement (BRAA) on the size and function of single slow- and fast-twitch muscle fibers. Supplementing meals, the BRAA group consumed 16.5 g essential amino acids and 30 g sucrose at 1100, 1600, and 2100 h, and the BRHC subjects received 5 daily doses of 10–15 mg of oral hydrocortisone sodium succinate throughout bed rest. Bed rest induced atrophy and loss of force (mN) and power (µN·FL·s^–1) in single fibers was exacerbated by hypercortisolemia where soleus peak force declined by 23% in the type I fiber from a prevalue of 0.78 ± 0.02 to 0.60 ± 0.02 mN post bed rest (compared to a 7% decline with bed rest alone) and 27% in the type II fiber (1.10 ± 0.08 vs. 0.81 ± 0.05 mN). In the BRHC group, peak power dropped by 19, 15, and 11% in the soleus type I, and vastus lateralis (VL) type I and II fibers, respectively. The AA/CHO supplement protected against the bed rest-induced loss of peak force in the type I soleus and peak power in the VL type II fibers. These results provide evidence that an AA/CHO supplement might serve as a successful countermeasure to help preserve muscle function during periods of relative inactivity. isotonic contractile properties; peak force and power; calcium sensitivity; essential amino acids     

Central injections of noradrenaline and adrenaline differentially affect plasma free fatty acid and glucose in conscious pigeons (Columba livia)

The possible involvement of central noradrenergic and/or adrenergic circuits in central mechanisms controlling free fatty acids and glucose levels was investigated in conscious pigeons. The effects of intracerebroventricular injections of noradrenaline (80 nmol) or adrenaline (80 nmol) on plasma free fatty acids and glucose concentrations were examined. The possible role of the autonomic nervous system, of sympathetic terminals and of pituitary hormone release in the metabolic responses induced by intracerebroventricular injections of adrenaline and noradrenaline was investigated by systemic pretreatment with a ganglionic blocker (hexamethonium, 1 mg/100 g), guanethidine (5 mg/100 g), and somatostatin (15 μg/100 g), respectively, 15 min before intracerebroventricular administration of adrenaline, noradrenaline or vehicle. Intracerebroventricular noradrenaline injections strongly increased plasma free fatty acid concentration but evoked no change in blood glucose levels, while adrenaline treatment increased glycemia without affecting free fatty acid levels. Hexamethonium did not block the increase in plasma free fatty acids induced by noradrenaline, while somatostatin pretreatment abolished noradrenaline-induced lipolysis during the experimental period. Adrenaline-induced hyperglycemia was blocked by systemic injections of somatostatin, hexamethonium and guanethidine. The present results suggest that: (1) adrenergic and noradrenergic mechanisms may participate in central control of blood glucose and free fatty acids, respectively, as observed in mammals, (2) noradrenaline-induced lipolysis may be mediated by pituitary mechanisms, and (3) postganglionic sympathetic fibers, possibly innervating the endocrine pancreas, may be involved in adrenaline-induced hyperglycemia. Accepted: 14 April 2000     

Blood amino acids concentration during insulin induced hypoglycemia in rats: the role of alanine and glutamine in glucose recovery

Summary. Our purpose was to determine the blood amino acid concentration during insulin induced hypoglycemia (IIH) and examine if the administration of alanine or glutamine could help glycemia recovery in fasted rats. IIH was obtained by an intraperitoneal injection of regular insulin (1.0 U/kg). The blood levels of the majority of amino acids, including alanine and glutamine were decreased (P < 0.05) during IIH and this change correlates well with the duration than the intensity of hypoglycemia. On the other hand, the oral and intraperitoneal administration of alanine (100 mg/kg) or glutamine (100 mg/kg) accelerates glucose recovery. This effect was partly at least consequence of the increased capacity of the livers from IIH group to produce glucose from alanine and glutamine. It was concluded that the blood amino acids availability during IIH, particularly alanine and glutamine, play a pivotal role in recovery from hypoglycemia.     

Isolation of freeze-tolerant laboratory strains of Saccharomyces cerevisiae from proline-analogue-resistant mutants

Since some amino acids, polyols and sugars in cells are thought to be osmoprotectants, we expected that several amino acids might also contribute to enhancing freeze tolerance in yeast cells. In fact, proline and charged amino acids such as glutamate, arginine and lysine showed a marked cryoprotective activity nearly equivalent to that of glycerol or trehalose, both known as major cryoprotectants for Saccharomyces cerevisiae. To investigate the cryoprotective effect of proline on the freezing stress of yeast, we isolated proline-analogue-resistant mutants derived from a proline-non-utilizing strain of S. cerevisiae. When cultured in liquid minimal medium, many mutants showed a prominent increase, two- to approximately tenfold, in cell viability compared to the parent after freezing in the medium at −20 °C for 1 week. Some of the freeze-tolerant mutants were found to accumulate a higher amount of proline, as well as of glutamate and arginine which are involved in proline metabolism. It was also observed that proline-non-utilizer and the freeze-tolerant mutants were able to grow against osmotic stress. These results suggest that the increased flux in the meta-bolic pathway of specific amino acids such as proline is effective for breeding novel freeze-tolerant yeasts. Received: 6 November 1996 / Accepted: 7 December 1996     

The effect of severe eccentric exercise-induced muscle damage on plasma elastase, glutamine and zinc concentrations

The aim of this study was to determine if severe exercise-induced muscle damage alters the plasma concentrations of glutamine and zinc. Changes in plasma concentrations of glutamine, zinc and polymorphonuclear elastase (an index of phagocytic cell activation) were examined for up to 10 days following eccentric exercise of the knee extensors of one leg in eight untrained subjects. The exercise bout consisted of 20 repetitions of electrically stimulated eccentric muscle actions on an isokinetic dynamometer. Subjects experienced severe muscle soreness and large increases in plasma creatine kinase activity indicative of muscle fibre damage. Peak soreness occurred at 2 days post-exercise and peak creatine kinase activity [21714 (6416) U · l⁻¹, mean (SEM)] occurred at 3 days post-exercise (P < 0.01 compared with pre-exercise). Plasma elastase concentration was increased at 3 days post-exercise compared with pre-exercise (P < 0.05), and is presumably indicative of ongoing phagocytic leucocyte infiltration and activation in the damaged muscles. There were no significant changes in plasma zinc and glutamine concentrations in the days following eccentric exercise. We conclude that exercise-induced muscle damage does not produce changes in plasma glutamine or zinc concentrations despite evidence of phagocytic neutrophil activation. Accepted: 3 November 1997     

The effect of exercise intensity on hematuria in healthy male runners

The purpose of this study were: (1) to establish the prevalence of exercise-induced hematuria in a group of otherwise healthy male runners (n = 70), and (2) to investigate the role of exercise intensity in those runners who exhibited exercise-related hematuria (n = 10) by evaluating the effect of running and cycling at high and low intensities. The identified and recruited subjects participated in four different exercise protocols: (1) a 60-min treadmill run (RUN) at 90% of anaerobic threshold (Th_ae), (2) a 60-min leg cycle ergometer ride (BIKE) at 90% of Th_ae, (3) a 3×400-m sprint (SPRINT), each followed by 4 min of rest or light walking, and (4) 3×60-Wingate leg cycle ergometry tests, each followed by 4 min of rest or light cycling. The study employed a 3×4 (time by protocol) within-subjects design and dependent variables were measured before exercise, 4 min after, and 1 h after exercise, and included measurements of hematuria, proteinuria, urinary pH, serum haptoglobin concentration, serum creatine phosphokinase activity, plasma lactate concentration, and hemoglobin. The 400-m sprint at maximal effort significantly increased both hematuria and proteinuria (P < 0.01). Post-exercise hematuria for the SPRINT protocol was significantly different than that for the BIKE (P < 0.01) and RUN (P < 0.01) protocols. Due to the significant increase in hematuria and proteinuria following the SPRINT protocol, it was concluded that exercise-related changes in renal function were associated with weight-bearing exercise intensity rather than non-weight-bearing exercise duration. Accepted: 30 April 1998     

Changes in plasma and urinary taurine and amino acids in runners immediately and 24 h after a marathon

Summary. Changes in urinary and plasma taurine and amino acids have been evaluated in trained runners competing in the Rotterdam Marathon, 1998, both immediately after completing the event and 24 h after recovery. There were significant changes in the urinary amino acids excretion, the majority showing a significant decrease both immediately at the completion of the Marathon and after 24 h recovery. In contrast urinary taurine excretion increased immediately post Marathon, although not significantly as the range of results was wide. Such changes in urinary taurine correlated with percentage changes in plasma creatine kinase both immediately post race, (r = 0.972, P < 0.001), and 24 h later (r = 0.872, P < 0.001), possibly indicating that the source of the taurine was muscle. Significant correlations between the individual values for urinary and plasma amino acids in all of the athletes were calculated for taurine (r = 0.528), glycine (r = 0.853), threonine (r = 0.749), alanine (r = 0.747), serine (r = 0.620), glutamine (0.614), arginine (r = 0.507), histidine (r = 0.470) and valine (r = 0.486). Changes in the mean plasma concentrations of amino acids were comparable to our previously published data (Ward et al., 1999) the majority showing significant decreases immediately and 24 h post Marathon, such an adaptation being due primarily to their utilisation for gluconeogenesis. However, in contrast, the mean taurine concentrations were significantly elevated both post race, P < 0.01 and after 24 h, P < 0.05. The physiological response by the muscle to exhaustive exercise, particularly with regard to changes in plasma and urinary taurine concentrations remain to be elucidated, but is probably related to muscle function impairment. The increase in taurine urinary excretion could be used as an indicator of muscle damage occurring during exhaustive exercise. Whether taurine supplementation would minimise such changes is an interesting scientific question and merits investigation. Received January 6, 2000 / Accepted February 1, 2000     

Plasma amino acid levels in hyperosmolar nonketotic diabetic coma

The plasma amino acid levels in five patients with hyperosmolar nonketotic diabetic coma and in seven normal subjects were analysed. In the patients with hyperosmolar nonketotic diabetic coma, total amino acids were generally low, especially, the concentrations and the molar ratios of arginine, taurine and serine were significantly low, and ornithine decreased only at the concentration. The level of phenylalanine increased both at the concentration and the molar ratio, and tyrosine did only at the molar ratio. The significance of such changes in the plasma is discussed in relation to diabetic ketoacidosis or lactic acidosis.     

The effect of taurine depletion on the contractile properties and fatigue in fast-twitch skeletal muscle of the mouse

Summary. Taurine as well as tauret (retinyliden taurine) levels were measured in locust Locusta migratoria compound eyes. HPLC measurements revealed relatively low taurine levels (1.9 ± 0.16 mM) in dark-adapted eyes. Glutamate, aspartate and glycine levels were 2.0 ± 0.2, 2.7 ± 0.4 and 3.0 ± 0.37 mM, respectively, while GABA was present only in trace amounts. After about 4 h of light adaptation at 1500–2000 lx, amino acid levels in the compound eye were as follows: taurine, 1.8 ± 0.17 mM; glutamate, no change at 2.1 ± 0.2 mM; aspartate sharply increased to 4.7 ± 0.7 mM; glycine slightly decreased to 2.8 ± 0.3 mM; and GABA trace levels. In the compound eye of locust Locusta migratoria, the existence of endogenous tauret in micro-molar range was established. In the dark, levels were several times higher compared with compound eye after light adaptation 1500 lx for 3 h, as estimated by TLC in combination with spectral measurements. Existence of tauret in compound eye is of special interest because in the compound eye, rhodopsin regeneration is based on photoregeneration.