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1.
Role of osmoregulation in the actions of taurine 总被引:7,自引:0,他引:7
Summary. Taurine regulates an unusual number of biological phenomena, including heart rhythm, contractile function, blood pressure,
platelet aggregation, neuronal excitability, body temperature, learning, motor behavior, food consumption, eye sight, sperm
motility, cell proliferation and viability, energy metabolism and bile acid synthesis. Many of these actions are associated
with alterations in either ion transport or protein phosphorylation. Although the effects on ion transport have been attributed
to changes in membrane structure, they could be equally affected by a change in the activity of the affected transporters.
Three common ways of altering transporter activity is enhanced expression, changes in the phosphorylation status of the protein
and cytoskeletal changes. Interestingly, all three events are altered by osmotic stress. Since taurine is a key organic osmolyte
in most cells, the possibility that the effects of taurine on ion transport could be related to its osmoregulatory activity
was considered. This was accomplished by comparing the effects of taurine, cell swelling and cell shrinkage on the activities
of key ion channels and ion transporters. The review also compares the phosphorylation cascades initiated by osmotic stress
with some of the phosphorylation events triggered by taurine depletion or treatment. The data reveal that certain actions
of taurine are probably caused by the activation of osmotic-linked signaling pathways. Nonetheless, some of the actions of
taurine are unique and appear to be correlated with its membrane modulating and phosphorylation regulating activities.
Received January 25, 2000/Accepted January 31, 2000 相似文献
2.
Summary. Recent literature suggests that both caffeine and taurine can induce diuresis and natriuresis in rat and man. Although they
act via different cellular mechanisms, their diuretic actions might be additive. This is of considerable interest, as several
commercially available energy drinks contain both substances.
In this study we examined the possible diuretic effects of caffeine and taurine in a cross-over-design in which 12 healthy
male volunteers received each of 4 different test drinks (750 ml of energy drink containing 240 mg caffeine and 3 g taurine,
the three other test drinks either lacked caffeine, taurine or both) after restraining from fluids for 12 h.
Mixed model analyses demonstrated that urinary output and natriuresis were significantly increased by caffeine (mean differences
243 ml and 27 mmol; both p < 0.001) and that there were no such effects of taurine (mean differences 59 ml and −4 mmol). Additionally, urinary osmolarity
at baseline was significantly related to the urinary output (p < 0.001). Urine osmolarity values at baseline and in the 6 h urine collection did not differ significantly between treatments.
Taken together, our study demonstrates that diuretic and natriuretic effects of the tested energy drink were largely mediated
by caffeine. Taurine played no significant role in the fluid balance in moderately dehydrated healthy young consumers. Consequently,
the diuretic potential of energy drinks will not differ significantly from other caffeine containing beverages. 相似文献
3.
Summary. Caffeine- and taurine-containing drinks have been on the European market for about a decade, and research on the individual
constituents of these drinks indicates an improvement in cognitive performance resulting from consumption of such drinks.
In this double-blind, placebo-controlled study using 10 graduate students, we obtained the P300 components of event-related
potential (ERP) waveforms following an auditory oddball paradigm, measured motor reaction time, and applied the d2 test for
the assessment of attention. Status of mood was assessed by the “Basler-Befindlichkeitsbogen” questionnaire, a standard test
for evaluation of feelings of well-being. Measurements were made at night, prior to and starting one hour after consumption
of energy drink ingredients or placebo.
At the end of the experiment (midnight), P300 latency and motor reaction time were significantly longer compared with baseline
measurements in the placebo group, but were unchanged in the energy drink group. In the test system for evaluating feelings
of well-being, total scores, vitality scores and social extrovertedness scores were significantly decreased in the placebo
group but not in the energy drink group.
The findings clearly indicate that the mixture of three key ingredients of Red BullR Energy Drink used in the study (caffeine, taurine, glucuronolactone) have positive effects upon human mental performance
and mood. These effects may be mediated by the action of caffeine on purinergic (adenosinergic) receptors and taurine modulation
of receptors. As half of the study cohort were non-caffeine users, the described effects cannot be explained in terms of the
restoration of plasma caffeine levels to normal following caffeine withdrawal.
Received January 5, 2000/Accepted June 5, 2000 相似文献
4.
Interaction between the actions of taurine and angiotensin II 总被引:1,自引:0,他引:1
Summary. The amino acid, taurine, is an important nutrient found in very high concentration in excitable tissue. Cellular depletion
of taurine has been linked to developmental defects, retinal damage, immundeficiency, impaired cellular growth and the development
of a cardiomyopathy. These findings have encouraged the use of taurine in infant formula, nutritional supplements and energy
promoting drinks. Nonetheless, the use of taurine as a drug to treat specific diseases has been limited. One disease that
responds favorably to taurine therapy is congestive heart failure. In this review, we discuss three mechanisms that might
underlie the beneficial effect of taurine in heart failure. First, taurine promotes natriuresis and diuresis, presumably through
its osmoregulatory activity in the kidney, its modulation of atrial natriuretic factor secretion and its putative regulation
of vasopressin release. However, it remains to be determined whether taurine treatment promotes salt and water excretion in
humans with heart failure. Second, taurine mediates a modest positive inotropic effect by regulating [Na+]i and Na+/Ca2+ exchanger flux. Although this effect of taurine has not been examined in human tissue, it is significant that it bypasses
the major calcium transport defects found in the failing human heart. Third, taurine attenuates the actions of angiotensin
II on Ca2+ transport, protein synthesis and angiotensin II signaling. Through this mechanism taurine would be expected to minimize many
of the adverse actions of angiotensin II, including the induction of cardiac hypertrophy, volume overload and myocardial remodeling.
Since the ACE inhibitors are the mainstay in the treatment of congestive heart failure, this action of taurine is probably
very important.
Received November 10, 1998, Accepted May 19, 1999 相似文献
5.
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. 相似文献
6.
Summary. We studied in vivo production of taurine, hypotaurine and sulfate following subcutaneous administration of L-cysteinesulfinate (CSA) to rats and mice. When 5.0 mmol/kg of body weight of CSA was injected to rats, increased urinary
excretions of taurine, hypotaurine and sulfate in 24 h urine were 617, 52 and 1,767 μmol/kg, respectively. From these results
together with our previous data, sulfate production was calculated to be 1.6 times greater than taurine production. Increased
contents (μmol/g of wet tissue) over the control of taurine and hypotaurine in mouse tissues at 60 min after the injection
of 5.0 mmol/kg body weight of CSA were: liver, 3.5 and 9.9; kidney, 0.3 and 5.2; heart, 3.7 and 0.2; blood plasma, 0.4 and
0.2, respectively. Upon loading of hypotaurine or taurine, tissue contents of these amino acids in liver and kidney increased
greatly. Our results indicate that liver is the most active tissue for taurine production, followed by kidney, and that external
CSA, hypotaurine and taurine are easily taken up by these tissues. 相似文献
7.
Mühling J Nickolaus KA Matejec R Langefeld TW Harbach H Engel J Wolff M Weismüller K Fuchs M Welters ID Krüll M Heidt MC Hempelmann G 《Amino acids》2008,34(2):257-270
We examined the effects of beta-alanine (taurine analogue and taurine transport antagonist), taurine (regarding its role in neutrophil (PMN) immunonutrition) and taurine combined either with L-NAME (inhibitor of *NO-synthase), SNAP (*NO donor), DON (glutamine-analogue and inhibitor of glutamine-requiring enzymes), DFMO (inhibitor of ornithine-decarboxylase) and beta-alanine on neutrophil amino- and alpha-keto acid profiles or important PMN immune functions in order to establish whether taurine transport-, nitric oxide-, glutamine- or ornithine-dependent mechanisms are involved in any of the taurine-induced effects. According to the present findings, the taurine-mediated effect appears to be based primarily on a modulation of important transmembraneous transport mechanisms and only secondarily on directly or indirectly induced modifications in intragranulocytic amino- and alpha-keto acid homoeostasis or metabolism. Although a direct relation to the parallel observed immunological modifications can only be presumed, these results show very clearly that compositional modifications in the free intragranulocytic amino- and alpha keto-acid pools coinciding with changes in intragranulocytic taurine levels are relevant metabolic determinants that can significantly influence the magnitude and quality of the granulocytic immune response. 相似文献
8.
Effects of high salt diets and taurine on the development of hypertension in the stroke-prone spontaneously hypertensive rat 总被引:3,自引:0,他引:3
Summary. Taurine is present in high concentrations in mammalian tissues and has been implicated in cardiovascular control mechanisms.
The aim of the present study was to evaluate the ability of taurine to attenuate salt-induced elevations in blood pressure
and markers of damage to the kidney and cardiovascular system in stroke prone spontaneously hypertensive rats (SPSHR). Male
SPSHR (6 weeks old) were placed on high salt diets that contained 1% (w/w) NaCl added to their normal chow for 84 days and
then were switched to 3% added NaCl for the remaining 63 days of the study. SPSHR was given 1.5% taurine in the drinking water
(n = 8), a taurine free diet (n = 8) or normal chow (n = 8). A final control group (n = 6) was not given high salt diets.
High salt diets caused an acceleration in the development of hypertension in all groups. Taurine supplementation reduced ventricular
hypertrophy and decreased urinary excretion of protein and creatinine. The taurine free diet did not alter serum or urinary
excretion of taurine, but did result in elevated urinary nitrogen excretion, increased serum cholesterol levels, and impaired
performance in a spatial learning task. Alterations in dietary taurine intake did not alter urinary or serum electrolytes
(Na+, K+), but taurine supplementation did attenuate a rise in serum calcium seen with the high salt diets. Urinary excretion (μg/24
h) of epinephrine and dopamine was significantly reduced in SPSHR given 1% NaCl in the diet, but this effect was not seen
in SPSHR on taurine free or supplemented diets. Taurine supplementation showed cardioprotective and renoprotective effects
in SPSHR given high salt diets.
Received April 12, 1999/Accepted September 13, 1999 相似文献
9.
Summary. Using microdialysis, the effects of endogenous glutamate on extracellular concentrations of taurine in striatum and nucleus
accumbens of the awake rat were investigated. The glutamate uptake inhibitor L-trans-pyrrolidine-2,4-dicarboxylic acid (PDC) was used to increase the extracellular concentration of glutamate. PDC (1, 2 and
4 mM) produced a dose-related increase of extracellular concentrations of glutamate and taurine in striatum and nucleus accumbens.
Increases of extracellular taurine were significantly correlated with increases of extracellular glutamate, but not with PDC
doses, which suggests that endogenous glutamate produced the observed increases of extracellular taurine in striatum and nucleus
accumbens. The role of ionotropic glutamate receptors on the increases of taurine was also studied. In striatum, perfusion
of the antagonists of NMDA and AMPA/kainate glutamate receptors attenuated the increases of extracellular taurine. AMPA/kainate,
but not NMDA receptors, also reduced the increases of extracellular taurine in nucleus accumbens. These results suggest that
glutamate-taurine interactions exist in striatum and nucleus accumbens of the awake rat.
Received March 5, 1999/Accepted September 22, 1999 相似文献
10.
Hoe 140 abolishes the blood pressure lowering effect of taurine in high fructose-fed rats 总被引:1,自引:0,他引:1
Summary. High fructose feeding induces moderate increases in blood pressure of normal rats, associated with hyperinsulinemia, insulin resistance and impaired glucose tolerance. Increased vascular resistance, and sodium retention have been proposed to contribute to the blood pressure elevation in this model. Taurine, a sulphur-containing amino acid has been reported to have antihypertensive and antinatriuretic actions. In addition, taurine is shown to increase the excretion of nitrite and kinin availability and hence would be expected to improve the vascular tone. In the present study, the involvement of kinins in the blood pressure lowering effect of taurine was investigated by coadministration of Hoe 140, a kinin B2 receptor antagonist along with taurine. The effects of taurine on plasma and urinary concentrations of sodium and tissue kallikrein activity were studied in high fructose-fed rats. Fructose-fed rats had elevated blood pressure and decreased levels of sodium in urine. Treatment with 2% taurine in drinking water prevented the blood pressure elevation and coadministration of Hoe 140 abolished this effect of taurine in high fructose-fed rats. The findings confirm the antinatriuretic action of taurine and also suggest a role for the kinins in the mechanism of taurine action in diet-induced hypertension. 相似文献
11.
Summary. Caffeine, the most widely consumed psychostimulant drug, acutely stimulates motor behaviour and enhances dopamine agonists
actions whilst chronically it induces tolerance to either caffeine- or dopamine agonist-induced motor activating effects.
The present study examined whether subchronic caffeine administration (15 mg/kg, on alternate days for 14 days) induces enduring
modifications in caffeine- and amphetamine-mediated motor activity. To this end, motor activation and rotational behaviour
stimulated by either caffeine or D-amphetamine (0.5, 2 mg/kg), given 3 days after the last caffeine administration, were evaluated
in neurologically intact and unilaterally 6-hydroxydopamine-lesioned rats respectively. Subchronic caffeine resulted in an
increase in caffeine-induced motor and turning behaviour. Furthermore, caffeine pretreatment potentiated the motor effects
of amphetamine in both intact and 6-hydroxydopamine-lesioned rats. These results suggest that subchronic caffeine treatment
results in an enhancement of its motor stimulant effects, rather than in tolerance, and induces neuroadaptive facilitatory
changes in dopamine transmission. 相似文献
12.
Taurine and neural cell damage 总被引:22,自引:2,他引:20
Summary. The inhibitory amino acid taurine is an osmoregulator and neuromodulator, also exerting neuroprotective actions in neural
tissue. We review now the involvement of taurine in neuron-damaging conditions, including hypoxia, hypoglycemia, ischemia,
oxidative stress, and the presence of free radicals, metabolic poisons and an excess of ammonia. The brain concentration of
taurine is increased in several models of ischemic injury in vivo. Cell-damaging conditions which perturb the oxidative metabolism
needed for active transport across cell membranes generally reduce taurine uptake in vitro, immature brain tissue being more
tolerant to the lack of oxygen. In ischemia nonsaturable diffusion increases considerably. Both basal and K+-stimulated release of taurine in the hippocampus in vitro is markedly enhanced under cell-damaging conditions, ischemia,
free radicals and metabolic poisons being the most potent. Hypoxia, hypoglycemia, ischemia, free radicals and oxidative stress
also increase the initial basal release of taurine in cerebellar granule neurons, while the release is only moderately enhanced
in hypoxia and ischemia in cerebral cortical astrocytes. The taurine release induced by ischemia is for the most part Ca2+-independent, a Ca2+-dependent mechanism being discernible only in hippocampal slices from developing mice. Moreover, a considerable portion of
hippocampal taurine release in ischemia is mediated by the reversal of Na+-dependent transporters. The enhanced release in adults may comprise a swelling-induced component through Cl− channels, which is not discernible in developing mice. Excitotoxic concentrations of glutamate also potentiate taurine release
in mouse hippocampal slices. The ability of ionotropic glutamate receptor agonists to evoke taurine release varies under different
cell-damaging conditions, the N-methyl-D-aspartate-evoked release being clearly receptor-mediated in ischemia. Neurotoxic
ammonia has been shown to provoke taurine release from different brain preparations, indicating that the ammonia-induced release
may modify neuronal excitability in hyperammonic conditions. Taurine released simultaneously with an excess of excitatory
amino acids in the hippocampus under ischemic and other neuron-damaging conditions may constitute an important protective
mechanism against excitotoxicity, counteracting the harmful effects which lead to neuronal death. The release of taurine may
prevent excitation from reaching neurotoxic levels.
Received January 25, 2000/Accepted January 31, 2000 相似文献
13.
Guz G Oz E Lortlar N Ulusu NN Nurlu N Demirogullari B Omeroglu S Sert S Karasu C 《Amino acids》2007,32(3):405-411
Summary. Ischemia-reperfusion (I/R) injury is one of the most common causes of renal dysfunction. Taurine is an endogenous antioxidant
and a membrane-stabilizing, intracellular, free beta-amino acid. It has been demonstrated to have protective effects against
I/R injuries to tissues other than kidney. The aim of this study was to determine whether taurine has a beneficial role in
renal I/R injury. Forty Wistar-Albino rats were allocated into four groups as follows: sham, taurine, I/R, and I/R + taurine.
Taurine 7.5 mg/kg was given intra-peritoneally to rats in the groups taurine and I/R + taurine. Renal I/R was achieved by
occluding the renal arteries bilaterally for 40 min, followed by 6 h of reperfusion. Immediately thereafter, blood was drawn
and tissue samples were harvested to measure 1) serum levels of BUN and creatinine; 2) serum and/or tissue levels of malondialdehyde
(MDA), glutathione (GSH), glucose 6-phosphate dehydrogenase (G-6PD), 6-phosphogluconate dehydrogenase (6-PGD) and glutathione
reductase (GSH-red); 3) renal morphology; and 4) immunohistochemical staining for P-selectin. Taurine administration reduced
I/R-induced increases in serum BUN and creatinine, and serum and tissue MDA levels (p < 0.05). Additionally, taurine lessened
the reductions in serum and tissue glutathione levels secondary to I/R (p < 0.05). Taurine also attenuated histopathologic
evidence of renal injury, and reduced I/R-induced P-selectin immunoreactivity (p < 0.05). Overall, then, taurine administration
appears to reduce the injurious effects of I/R on kidney. 相似文献
14.
Summary. The effects of Red Bull Energy Drink, which includes taurine, glucuronolactone, and caffeine amongst the ingredients, were
examined over 3 studies in a total of 36 volunteers. Assessments included psychomotor performance (reaction time, concentration,
memory), subjective alertness and physical endurance. When compared with control drinks, Red Bull Energy Drink significantly
(P < 0.05) improved aerobic endurance (maintaining 65–75% max. heart rate) and anaerobic performance (maintaining max. speed)
on cycle ergometers. Significant improvements in mental performance included choice reaction time, concentration (number cancellation)
and memory (immediate recall), which reflected increased subjective alertness. These consistent and wide ranging improvements
in performance are interpreted as reflecting the effects of the combination of ingredients.
Received March 20, 2000 Accepted May 25, 2000 相似文献
15.
Taurine release modified by GABAergic agents in hippocampal slices from adult and developing mice 总被引:2,自引:0,他引:2
Summary. In order to characterize the possible regulation of taurine release by GABAergic terminals, the effects of several agonists
and antagonists of GABA receptors on the basal and K+-stimulated release of [3H]taurine were investigated in hippocampal slices from adult (3-month-old) and developing (7-day-old) mice using a superfusion
system. Taurine release was concentration-dependently potentiated by GABA, which effect was reduced by phaclofen, saclofen
and (1,2,5,6-tetrahydropyridin-4-yl)methylphosphinic acid (TPMPA) at both ages, suggesting regulation by both GABAB and GABAC receptors. The involvement of GABAA receptors could not be excluded since the antagonist bicuculline was able to affect both basal and K+-evoked taurine release. Furthermore, several GABAB receptor effectors were able to inhibit K+-stimulated taurine release in the adults, while the GABAC receptor agonists trans-4-aminocrotonic acid (TACA) and cis-4-aminocrotonic acid (CACA) potentiated this release. The potentiation
of taurine release by agents acting on the three types of GABA receptors in both adult and developing hippocampus further
indicates the involvement of transporters operating in an outward direction. This inference is corroborated by the moderate
but significant inhibition of taurine uptake by the same compounds.
Received June 28, 1999, Accepted August 31, 1999 相似文献
16.
Parildar-Karpuzoğlu H Doğru-Abbasoğlu S Balkan J Aykaç-Toker G Uysal M 《Amino acids》2007,32(1):115-119
Summary. We aimed to investigate the effect of decreased taurine levels on endogenous and induced lipid peroxide levels in liver, brain,
heart and erythrocytes as well as prooxidant and antioxidant balance in the liver of rats administered β-alanine (3%, w/v)
in drinking water for 1 month to decrease taurine levels of tissues. This treatment caused significant decreases in taurine
levels of liver (86%), brain (36%) and heart (15%). We found that endogenous and ascorbic acid-, NADPH- and cumene hydroperoxide-induced
malondialdehyde (MDA) levels did not change in the liver, brain and heart homogenates following β-alanine treatment. Also,
H2O2-induced MDA levels remained unchanged in erythrocytes. In addition, we did not observe any changes in levels of MDA, diene
conjugates, glutathione, α-tocopherol, ascorbic acid and the activities of superoxide dismutase, glutathione peroxidase and
glutathione transferase in the liver. According to this, buffering or sequestering capacity of tissues to exogenous stimuli
was not influenced by reduced taurine levels in tissues of rats. 相似文献
17.
Sved DW Godsey JL Ledyard SL Mahoney AP Stetson PL Ho S Myers NR Resnis P Renwick AG 《Amino acids》2007,32(4):459-466
Summary. Three biodisposition studies with taurine were performed in male and female adult rats at dosages of 30 and 300 mg/kg. A single
oral dose of 14C-taurine was rapidly absorbed, distributed to tissues and excreted unchanged in urine. Elimination of radioactivity from
intracellular pools was slow. Pre-treatment of animals for 14 days with unlabelled taurine did not significantly affect the
fate of 14C-taurine. At the higher dose there was more extensive excretion combined with a lower percentage of the dose in the carcass,
indicating the possibility of saturation of the tubular reabsorption mechanism for taurine. Daily administration of unlabelled
taurine for 14 days did not result in an increase in total taurine in the brain. The data indicate that exogenous taurine
rapidly equilibrates with endogenous body pools and that any excess is rapidly eliminated by the kidneys. 相似文献
18.
Summary. Nitric oxide (NO) has been shown to regulate neurotransmitter release in the brain; both inhibitory and excitatory effects
have been seen. Taurine is essential for the development and survival of neural cells and protects them under cell-damaging
conditions. In the brain stem, it regulates many vital functions such as cardiovascular control and arterial blood pressure.
Now we studied the effects of the NO-generating compounds hydroxylamine (HA), S-nitroso-N-acetylpenicillamine (SNAP) and sodium
nitroprusside (SNP) on the release of preloaded [3H]taurine under normal and ischemic conditions in slices prepared from the mouse brain stem from developing (7-day-old) to
young adult (3-month-old) mice. In general, the effects of NO on the release were somewhat complex and difficult to explain,
as expected from the multifunctional role of NO in the central nervous system. The basal initial release under normal conditions
was enhanced by the NO donors 5 mM HA and 1.0 mM SNAP at both ages, but SNP was inhibitory in developing mice. The release
was markedly enhanced by K+ stimulation. The effects of HA, SNAP and SNP on the basal release were not antagonized by the NO synthase inhibitor NG-nitro-L-arginine (L-NNA, 1.0 mM), demonstrating that mechanisms other than NO synthesis are involved. Taurine release in
developing mice in the presence of SNP was reduced by the inhibitor of soluble guanylate cyclase, 1H-(1,2,3)oxadiazolo(4,3-a)quinoxalin-1-one
(ODQ), indicating the possible involvement of cGMP. In normoxia, N-methyl-D-aspartate (NMDA, 1.0 mM) enhanced the SNAP- and
HA-evoked taurine release in developing mice and the HA-evoked release in adults. In ischemia, both K+ stimulation and NMDA potentiated the NO-induced release, particularly in the immature mice, probably without the involvement
of the NO synthase or cGMP. The substantial release of taurine in the developing brain stem evoked by NO donors together with
NMDA might represent signs of important mechanisms against excitotoxicity which protect the brain stem under cell-damaging
conditions.
Authors’ address: Prof. Pirjo Saransaari, Brain Research Center, Medical School University of Tampere, Tampere, FIN-3 3014,
Finland 相似文献
19.
Summary. The objective of this study was to assess the effect of taurine-depletion on cardiovascular responses of rat to vasoactive
agents. Male Wistar-Kyoto (WKY) rats were given either tap water (control) or 3% β-alanine (taurine-depleted) for three weeks.
Thereafter, mean arterial pressure (MAP) and heart rate of the freely moving animal were measured in response to vasoactive
agents. Administration of phenylephine (5–40 μg/kg/min; i.v.) resulted in a similar and significant increase in MAP but a
reduction in heart rate in both control and taurine-depleted groups. On the other hand, administration of sodium nitroprusside
(15–300 μg/kg/min; i.v.) elicited a similar and significant reduction in MAP but increased heart rate in both groups. Lack
of a differential response to phenylephrine and sodium nitroprusside between the two groups suggests that baroreflex regulation
of cardiovascular function is not adversely affected by taurine-depletion. Administration of angiotensin II (0.1–3.0 μg/kg/min;
i.v.) resulted in a dose-related increase in the pressor response and a decrease in heart rate in both groups. However, angiotensin
II-induced pressor response was reduced in the taurine-depleted compared to the control rats (p < 0.05); heart rate was similarly
reduced in both groups. Acute exposure to β-alanine (3 g/kg; i.v., 30-minutes) did not alter angiotensin II-induced hemodynamic
responses. Similarly, incubation of aortic rings with β-alanine (40 mM, 30 minutes) did not affect the contractile responses
to angiotensin II. The results suggest that β-alanine, per se, does not affect angiotensin II-induced responses in rat. However, β-alanine-induced taurine depletion is associated with
a reduction in the pressor response to angiotensin II without impairing baroreflex function.
Received December 17, 1999/Accepted January 12, 2000 相似文献
20.
Chronic intake of caffeine during gestation down regulates metabotropic glutamate receptors in maternal and fetal rat heart 总被引:1,自引:0,他引:1
Summary. Caffeine is the most widely consumed substance in the world which antagonizes adenosine effects. Adenosine acting through
A1 receptors inhibits glutamate release which binds to metabotropic glutamate receptors (mGluRs). Recently, we have shown that
maternal caffeine intake during gestation causes down-regulation of A1 and metabotropic glutamate receptors in the brain of both rat mothers and fetuses. In the present work we provide evidence
that caffeine also affects receptors in hearts, causing a decrease in mGluRs from both maternal and fetal hearts. A decrease
in Gq/11 and PLC β1 proteins level was also observed in both tissues. However, phospholipase C activity was only affected in fetal heart, being
significantly decreased. These results suggest an in vivo cross-talk mechanism between adenosine and glutamate receptors in peripheral tissues. Therefore, special attention should
be paid to caffeine ingestion during gestation. 相似文献