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1.
Summary. Although there are a great number of studies concerning the uptake of taurine in several tissues, the regulation of taurine
transport has not been studied in the retina after lesioning the optic nerve. In the present study, isolated retinal cells
of the goldfish retina were used either immediatly after cell suspension or in culture. The high-affinity transport system
of [3H]taurine in these cells was sodium-, temperature- and energy-dependent, and was inhibited by hypotaurine and β-alanine, but
not by γ-aminobutyric acid. There was a decrease in the maximal velocity (Vmax) without modifications in the substrate affinity (Km) after optic axotomy. These changes were mantained for up to 15 days after the lesion. The results might be the summation
of mechanisms for providing extracellular taurine to be taken up by other retinal cells or eye structures, or regulation by
the substrate taurine, which increases after lesioning the optic nerve. The in vivo accumulation of [3H]taurine in the retina after intraocular injection of [3H]taurine was affected by crushing the optic nerve or by axotomy. A progressive retinal decrease in taurine transport was
observed after crushing the optic nerve, starting at 7 hours after surgery on the nerve. The uptake of [3H]taurine by the tectum was compensated in the animals that were subjected to crushing of the optic nerve, since the concentration
of [3H]taurine was only different from the control value 24 hours after the lesion, indicating an efficient transport by the remaining
axons. On the contrary, the low levels of [3H]taurine in the tectum after axotomy might be an index of the non-axonal origin of taurine in the tectum. Axonal transport
was illustrated by the differential presence of [3H]taurine in the intact or crushed optic nerve. The uptake of [3H]taurine into retinal cells in culture in the absence or in the presence of taurine might indicate the existence of an adaptive
regulation of taurine transport in this tissue, however taurine transport probably differentially occurs in specific populations
of retinal cells. The use of a purified preparation of cells might be useful for future studies on the modulation of taurine
transport by taurine in the retina and its role during regeneration.
Received June 11, 1999/Accepted August 31, 1999 相似文献
2.
3.
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
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. In the literature taurine is characterized as a non-specific growth or blood clotting factor, an antioxidant, a membrane
protector, or a regulator of calcium ion homeostasis, just as vitamins A, D, E, F, and K are similarly characterized. On the
basis of recent finding concerning the relationship between taurine and the aldehyde of vitamin A-retinal (Petrosian and Haroutounian,
1988, 1998; Petrosian et al., 1996), as well as on the basis of data from the literature, we now suggest a hypothesis that
taurine promotes the bioavailability of the lipid soluble vitamins A, D, E, K, and F, probably by forming different types
of water soluble, easily hydrolyzable complexes. It is quite possible that the ability of taurine to convert lipids and lipid
soluble substances into a water soluble state is the key to understanding the unusually wide diversity of biological phenomena
associated with taurine. This form of delivery may be an additional, secondary mechanism for the transport of lipid soluble
vitamins, which was probably acquired early in evolution, and remains extremely important for mammals and humans directly
after birth for a variety of physiological functions such as: vision in normal and in emergency situations, rapid blood clotting,
sperm eruption, and situations requiring a prompt consumption of lipid soluble vitamins characteristic of excitable systems.
Clearly, the role of taurine in the physiology of the water insoluble vitamins remains an enigma and is worthy of further
investigations.
Received December 23, 1999; Accepted December 28, 1999 相似文献
6.
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
7.
Summary. In human KB and LoVo cell lines, high affinity taurine uptake was strongly reduced in both a time and dose-dependent manner
by cumene hydroperoxide (CH) and to a lesser extent by hydrogen peroxide (H2O2). Uptake-inhibition was greater in multidrug resistant (MDR) cells than in their non-MDR counterparts. Basal taurine efflux
was unaffected by the oxidants. Lipid peroxidation levels closely correlated with the uptake inhibition levels, and were greater
in MDR cells than in their non-MDR counterparts. The two oxidants reduced the Vmax and, to a lesser extent, the affinity of
the transporter for taurine. They also reduced low affinity taurine uptake and, to a lesser extent, taurine diffusion. The
composition of the medium used for cell treatment, especially its pyruvate content, greatly affected the H2O2 effect. H2O2- or CH-induced reduction of the high affinity taurine uptake was unaffected by protein kinase C (PKC) inhibitors and by the
calmodulin antagonist W-13, ruling out the involvement of PKC and perhaps of calmodulin kinases in their effect.
Received October 2, 2000 Accepted February 13, 2001 相似文献
8.
Summary. The lancelet (amphioxus), a cephalochordate, is the closest invertebrate relative to vertebrates, with a simple vertebrate-like
body plan and a prototypical genome. We have determined D-aspartic acid (D-Asp) and major free L-amino acids (L-AAs) content
in the nervous system (neural tube) of the European amphioxus Branchiostoma lanceolatum, and have compared these values with those of molluscs and human brain. The B. lanceolatum neural tube contains relatively high amounts of L-Glu, L-Asp, L-Ala and L-Gly. Thus, the amphioxus neural tube has in common
with the molluscan and human nervous systems the presence of appreciable amounts of L-Glu and L-Asp, which suggests that they
are the most common neurotransmitters among these phylogenetically distant animal groups. The relatively high concentration
of L-Ala in amphioxus is consistent with that found in molluscs and the low concentration of taurine is consistent with that
described in the human brain.
The D-Asp concentration, very high in the molluscan nervous system, was rather low in amphioxus, although a little higher
than the extremely low amounts observed in the human brain. Our data on free amino acids composition is in agreement with
the intermediate phylogenetic position of cephalochordates, in terms of the evolutionary transition from simple to complex
neural systems. 相似文献
9.
Relationship of taurine and other amino acids in plasma and in neutrophils of septic trauma patients
Engel JM Mühling J Weiss S Kärcher B Löhr T Menges T Little S Hempelmann G 《Amino acids》2006,30(1):87-94
Summary. Recently, an interdependency of plasma taurine and other amino acids as well as metabolic and clinical variables implicating
therapeutic options was reported. This result may be an indication that plasma taurine levels are directly related to intracellular
levels. Therefore, the aim of this study was to analyse the possible relationship between taurine levels in plasma and in
neutrophils, the relationship to other amino acids, and variables quantifying metabolic impairment and severity of sepsis
in multiple trauma patients developing sepsis. After multiple trauma taurine decreased significantly in plasma in thirty-two
patients as well as within the neutrophil and does not recover in sepsis. Lower individual levels in the neutrophil did not
follow lower individual levels in plasma and no correlation of taurine in plasma and in the neutrophils could be observed.
In sepsis, only plasma showed an interdependency of taurine, aspartate, and glutamate. No association between taurine plasma
or intracellular levels and SOFA score as indicator for severity of sepsis or metabolic variables was observed. After multiple
trauma and in sepsis, taurine uptake in cells (which is regulated in different ways), and intracellular taurine (which serves
e.g. as an osmolyte) can be influenced. Therefore a prediction of the neutrophil taurine pool seems not fully possible from
taurine plasma levels. Intracellular taurine has some unique properties explaining the missing interdependency despite some
similarities in osmoregulation and metabolic interactions to other amino acids. The association of taurine, aspartate, and
glutamate in plasma cannot be simply transferred to the neutrophils intracellular level. The clinical meaning of the plasma
correlation remains unclear. A dependency of plasma and neutrophil taurine to severity of sepsis and to metabolic variables
seems not possible because of the multifactorial pathophysiology of sepsis. 相似文献
10.
Summary. Taurine transport in human intestinal epithelial Caco-2 cells was down-regulated by culturing the cells in taurine-containing
media and was up-regulated in a taurine-free medium. This adaptive regulation was associated with changes in both the Vmax
and Km values of taurine transport. A change in the mRNA level of the taurine transporter (TAUT) in this regulation was also
observed. The presence of such a regulatory mechanism for maintaining the intracellular taurine content at a certain level
suggests that taurine plays an important role in the intestinal cell functions. The intracellular taurine content was increased
when Caco-2 cells were exposed to a hypertonic stress. TAUT was up-regulated via the increased expression of TAUT mRNA in
the hypertonic cells, suggesting that taurine serves as an osmolyte and protects the cells from osmotic stress. Similar up-regulation
of TAUT was observed in the small intestine of water-deprived rats.
Received January 25, 2000/Accepted January 31, 2000 相似文献
11.
Summary. Taurine has been reported to enhance cholesterol 7α-hydroxylase (CYP7A1) mRNA expression in animal models. However, no in vitro studies of this effect have been reported. The Hep G2 human hepatoma cell line has been recognized as a good model for studying
the regulation of human CYP7A1. This work characterizes the effects of taurine on CYP7A1 mRNA levels of Hep G2 cells in a
dose- and time-dependent manner. In the dose-dependent experiment, Hep G2 cells were treated with 0, 2, 10 or 20 mM taurine
in the presence or absence of cholesterol 0.2 mM for 48 h. In the time-dependent experiment, Hep G2 cells were treated with
0 or 20 mM taurine for 4, 24 and 48 h with and without cholesterol 0.2 mM. Our data revealed that taurine showed time- and
dose-response effects on CYP7A1 mRNA levels in Hep G2 cells. However, glycine – a structural analogue of taurine – did not
have an effect on CYP7A1 gene expression. These results show that, in agreement to previous studies on animal models, taurine
induces the mRNA levels of CYP7A1 in Hep G2 cells, which could enhance cholesterol conversion into bile acids. Also, Hep G2
cell line may be an appropriate model to study the effects of taurine on human cholesterol metabolism. 相似文献
12.
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
13.
D.T. Thwaites D. Markovich H. Murer N.L. Simmons 《The Journal of membrane biology》1996,151(3):215-224
The nature of transepithelial and cellular transport of the dibasic amino acid lysine in human intestinal epithelial Caco-2
cells has been characterized. Intracellular accumulation of lysine across both the apical and basolateral membranes consists
of a Na+-independent, membrane potential-sensitive uptake. Na+-independent lysine uptake at the basolateral membrane exceeds that at the apical membrane. Lysine uptake consists of both
saturable and nonsaturable components. Na+-independent lysine uptake at both membranes is inhibited by lysine, arginine, alanine, histidine, methionine, leucine, cystine,
cysteine and homoserine. In contrast, proline and taurine are without inhibitory effects at both membranes. Fractional Na+-independent lysine efflux from preloaded epithelial layers is greater at the basolateral membrane and shows trans-stimulation
across both epithelial borders by lysine, arginine, alanine, histidine, methionine, and leucine but not proline and taurine.
Na+-independent lysine influx (10 μm) in the presence of 10 mm homoserine shows further concentration dependent inhibition by lysine. Taken together, these data are consistent with lysine
transport being mediated by systems bo,+, y+ and a component of very low affinity (nonsaturable) at both membranes. The relative contribution to lysine uptake at each
membrane surface (at 10 μm lysine), normalized to total apical uptake (100%), is apical bo,+ (47%), y+ (27%) and the nonsaturable component (26%), and basal bo,+ (446%), y+ (276%) and the nonsaturable component (20%). Northern analysis shows hybridization of Caco-2 poly(A)+RNA with a human rBAT cDNA probe.
Received: 3 July 1995/Revised: 6 February 1996 相似文献
14.
Summary. Calcium ion (Ca2+) uptake was measured in rod outer segments (ROS) isolated from rat retina in the presence of varying concentrations of CaCl2 in the incubation buffer (1.0–2.5 mM). It is known that taurine increases Ca2+ uptake in rat ROS in the presence of ATP and at low concentrations of CaCl2 (Lombardini, 1985a); taurine produces no significant effects when CaCl2 concentrations are increased to 1.0 and 2.5 mM. With the removal of both taurine and ATP, Ca2+ uptake in rat ROS increased significantly in the presence of 2.5 mM CaCl2. Taurine treatment in the absence of ATP was effective in decreasing Ca2+ uptake at the higher levels of CaCl2 (2.0 and 2.5 mM). Similar effects were observed with ATP treatment. The data suggest that taurine and ATP, alone or in combination,
limit the capacity of the rat ROS to take up Ca2+ to the extent that a stable uptake level is achieved under conditions of increasing extracellular Ca2+, indicating a protective role for both agents against calcium toxicity.
Received January 25, 2000/Accepted January 31, 2000 相似文献
15.
Taurine transporter is expressed in vascular smooth muscle cells 总被引:2,自引:0,他引:2
Summary. The regulation of vascular smooth muscle cells (VSMCs) function by taurine has been a subject of increasing interest and investigation,
and taurine is taken up into cells through a specific transporter system, the taurine transporter (TAUT). In the present study,
we examined the expression of TAUT in VSMCs and the kinetic parameters of the uptake process of TAUT in VSMCs. RT-PCR and
western blot demonstrated that the mRNA and protein of TAUT was expressed in VSMCs in vitro. Immunohistochemistry using antibody
for TAUT revealed the expression of this protein in rat thoracic aorta. The maximal [3H]taurine uptake rate in VSMCs was 37.75 ± 3.13 pmol/min per mg of protein, with a K
m
value of 5.42 ± 0.81 μM. Thus, VSMCs are able to express a functional taurine transporter. The regulation and detailed function
of taurine and TAUT in VSMCs remain unclear, but our findings suggest a functional role for them in VSMCs metabolism. 相似文献
16.
Summary. In daunorubicin resistant Ehrlich ascites tumor cells (DNR), the initial taurine uptake was reduced by 56% as compared to
the parental, drug sensitive Ehrlich cells. Kinetic experiments indicated that taurine uptake in Ehrlich cells occurs via
both high- and low-affinity transporters. The maximal rate constant for the initial taurine uptake was reduced by 45% (high-affinity
system) and 49% (low affinity system) in the resistant subline whereas the affinity of the transporters to taurine was unchanged.
By immunoblotting we identified 3 TauT protein bands in the 50–70 kDa region. A visible reduction in the intensity of the
band with the lowest molecular weight was observed in resistant cells. Quantitative RT-PCR indicated a significant reduction
in the amount of taurine transporter mRNA in the resistant cells. Drug resistance in DNR Ehrlich cells is associated with
overexpression of the mdr1 gene product P-glycoprotein (P-gp). Using 5 progressively DNR resistant Ehrlich cell sublines with different P-gp expression
pattern no correlation between taurine uptake and P-gp expression was found. Taurine uptake in MDR1 transfected NIH/3T3 mouse fibroblasts was in contrast to the findings in Ehrlich cells increased compared to the parental
fibroblasts. It is concluded that the reduced taurine uptake in resistant Ehrlich cells reflects a down regulation of the
taurine transporter at the mRNA and protein level and it is most probably not related to P-gp overexpression.
Received October 22, 2001 Accepted November 26, 2001 相似文献
17.
Summary. Hepatocytes were cultured for 3 days as spheroids (aggregates) or as monolayers in basal medium and in sulfur amino acid-supplemented
media. Cultured hepatocytes had low levels of cysteine dioxygenase (CDO) activity and normal levels of γ-glutamylcysteine
synthetase (GCS) and cysteinesulfinate decarboxylase (CSDC) activities compared to freshly isolated cells. CDO activity increased
and GCS activity decreased in a dose-response manner in cells cultured in either methionine- or cysteine-supplemented media.
CSDC activity was not significantly affected by methionine supplementation. Changes in CDO and GCS were associated with changes
in cysteine catabolism to taurine plus sulfate and in synthesis of glutathione, respectively. These responses are similar
to those observed in liver of intact rats fed diets supplemented with sulfur amino acids. A near-maximal response of CDO or
GCS activity was observed when the medium contained 1.0 mmol/L of methionine plus cyst(e)ine. Changes in CDO and GCS activities
did not appear to be mediated by changes in the intracellular glutathione concentration. Cultured hepatocytes offer a useful
model for further studies of cysteine metabolism and its regulation in response to sulfur amino acid availability.
Received June 2, 1999/Accepted September 16, 1999 相似文献
18.
Leaf and minor vein structure were studied in Arabidopsis thaliana (L.) Heynh. to gain insight into the mechanism(s) of phloem loading. Vein density (length of veins per unit leaf area) is
extremely low. Almost all veins are intimately associated with the mesophyll and are probably involved in loading. In transverse
sections of veins there are, on average, two companion cells for each sieve element. Phloem parenchyma cells appear to be
specialized for delivery of photoassimilate from the bundle sheath to sieve element-companion cell complexes: they make numerous
contacts with the bundle sheath and with companion cells and they have transfer cell wall ingrowths where they are in contact
with sieve elements. Plasmodesmatal frequencies are high at interfaces involving phloem parenchyma cells. The plasmodesmata
between phloem parenchyma cells and companion cells are structurally distinct in that there are several branches on the phloem
parenchyma cell side of the wall and only one branch on the companion cell side. Most of the translocated sugar in A. thaliana is sucrose, but raffinose is also transported. Based on structural evidence, the most likely route of sucrose transport is
from bundle sheath to phloem parenchyma cells through plasmodesmata, followed by efflux into the apoplasm across wall ingrowths
and carrier-mediated uptake into the sieve element-companion cell complex.
Received: 5 October 1999 / Accepted: 20 November 1999 相似文献
19.
Mühling J Burchert D Langefeld TW Matejec R Harbach H Engel J Wolff M Welters ID Fuchs M Menges T Krüll M Hempelmann G 《Amino acids》2007,33(3):511-524
Summary. We examined the effects of DON [glutamine-analogue and inhibitor of glutamine-requiring enzymes], alanyl-glutamine (regarding
its role in neutrophil immunonutrition) and alanyl-glutamine combined with L-NAME, SNAP, DON, β-alanine and DFMO on neutrophil
amino and α-keto acid concentrations or important neutrophil immune functions in order to establish whether an inhibitor of
•NO-synthase [L-NAME], an •NO donor [SNAP], an analogue of taurine and a taurine transport antagonist [β-alanine], an inhibitor
of ornithine-decarboxylase [DFMO] as well as DON could influence any of the alanyl-glutamine-induced effects. In summary,
irrespective of which pharmacological, metabolism-inhibiting or receptor-mediated mechanisms were involved, our results showed
that impairment of granulocytic glutamine uptake, modulation of intracellular glutamine metabolisation and/or de novo synthesis
as well as a blockade of important glutamine-dependent metabolic processes may led to significant modifications of physiological
and immunological functions of the affected cells. 相似文献
20.
Summary. The effects of chronic taurine treatment on the reactivity of the aorta form male Wistar-Kyoto rats were investigated. Contractile
responses to norepinephrine (NE) and potassium chloride (KCl) were attenuated in aortic rings from taurine-treated rats as
compared to controls both in the absence and presence of endothelium. However, the degree of attenuation was greater in endothelium-intact
tissues contracted with NE. Acetylcholine (Ach)-induced relaxation responses were augmented in endothelium-intact vessels
from rats supplemented with taurine compared to the responses observed in control preparations. Relaxation responses of the
aortae from control and taurine-treated rats to sodium nitroprusside (SNP) were not different from each other. Our results
suggest that taurine treatment attenuates vascular contractility nonspecifically and this effect is partly mediated via the
endothelium.
Received December 20, 1999/Accepted January 9, 2000 相似文献