The effects of taurine and hypotaurine on in vitro fertilization in the golden hamster

Taurine and hypotaurine were examined for their efficacy in replacing sperm motility factor (SMF), prepared from bovine adrenal cortex, for in vitro fertilization in the golden hamster. Combinations of these amino acids at concentrations of 0.001, 0.01, 0.1, and 1 mM together with 16 μM isoproterenol (a catecholamine β-agonist) were added to the sperm incubations. After three hours of sperm preincubation, oviductal eggs were added to the sperm suspensions and examined for penetration and stage of fertilization after three or five hours of culture. At 0.001 mM, neither taurine or hypotaurine was capable of maintaining motility of hamster sperm for four to 4½ hours or of inducing fertilization. With all other concentrations, both amino acids were found to maintain motility of sperm as well as SMF. Hypotaurine stimulated motility to a greater extent than taurine and both required isoproterenol for the greatest motility. A low proportion of cumulus-free ova were fertilized when sperm were preincubated with either amino acid alone over the range of 0.01 to 1 mM; however, over 80% fertilization was consistently obtained when isoproterenol was also present during sperm incubation. Proportions of ova fertilized with taurine or hypotaurine present during sperm preincubation were comparable to those achieved with SMF. The possibility that taurine or hypotaurine is the sperm motility factor is discussed. After three hours of sperm/egg incubation, a lag in the early events of fertilization was observed in experimental groups treated with one of the amino acids (0.01 mM) alone compared with groups treated with isoproterenol present. However, if sperm/egg incubation was extended from three to five hours, no increase in number of eggs penetrated was found. Therefore, the delay observed at three hours was considered a function of fewer numbers of capacitated sperm present in the absence of isoproterenol rather than of the need for an extended capacitation time.     

高糖对培养大鼠心肌细胞牛磺酸转运的影响及其可能机制

目的：观察不同浓度葡萄糖对细胞牛磺酸(taurine)转运功能的影响。方法：在培养的大鼠心肌细胞上,用^3H标记的牛磺酸测定细胞牛磺酸转运和竞争性定量RTPCR测定细胞牛磺酸转运体(TAUT)mRNA含量。结果：不同浓度葡萄糖(10～30mmol/L)孵育,抑制细胞^3H-牛磺酸转运,呈时间依赖性。与对照组比较,高糖(20mmol／L和30mmol／L)使心肌细胞牛磺酸摄入量显著减少,其^3H-牛磺酸转运的最大速率(Vmax)减少,心肌细胞TAUTmRNA含量较对照组减少。结论：高糖抑制心肌细胞牛磺酸转运,这与TAUT的牛磺酸结合位点减少和TAUT基因转录水平下调有关。     

Inhibition of hamster sperm Na+, K+-ATPase activity by taurine and hypotaurine

Taurine, hypotaurine and the structural analogue, beta-alanine, were tested for their effects on Na+, K+-ATPase activity of crude homogenates prepared from washed cauda epididymal hamster sperm. Preincubation with 0.1-10 mM taurine or hypotaurine inhibited Na+, K+-ATPase in a dose-dependent manner, while beta-alanine had an inhibitory effect only at 10 mM. The results of this study are the first evidence to demonstrate inhibition of Na+, K+-ATPase activity by taurine and hypotaurine and are discussed in relation to the ability of these compounds to sustain hamster sperm motility and fertility.     

The relationship between sodium and high-affinity taurine uptake in hypothalamic crude P2 synaptosomal preparations

Two uptake systems for taurine transport in a rat hypothalamic crude synaptosomal preparation were identified. The true transport constants were, for the high-affinity uptake system,K _m=240 M andV (maximum velocity)=400 nmol/g protein/min, and for the low-affinity uptake system.K _m=5290 M and V=1640 nmol/g protein/min. The initial velocity of high-affinity taurine uptake by the crude synaptosomal preparation was studied as a function of sodium and taurine concentration. Hill plots were constructed from these data. The requirement of high-affinity taurine uptake on a sodium gradient was examined by utilizing monensin, and the metabolic poisons, 2,4-dinitrophenol and ouabain. The major findings are as follows: 1) One sodium ion is co-transported with each taurine molecule; 2) the high-affinity uptake process is driven by the sodium concentration gradient across the membrane; 3) sodium increases the maximal velocity rather than the affinity of the high-affinity taurine carrier for the taurine molecule; 4) one taurine molecule is transported per carrier for both the high- and low-affinity taurine uptake systems; and 5) high-affinity taurine uptake is an energy-dependent process.     

Identification of a high affinity taurine transporter which is not dependent on chloride

Taurine transport by lactating gerbil mammary tissue has been examined. Taurine uptake is, mediated by a high-affinity system which is specific for -amino acids. The uptake of taurine is Na⁺-dependent but appears not to be obligatorly dependent upon Cl^–. Thus, replacing Na⁺ with choline almost abolished taurine uptake. Substituting Cl^– with NO ₃ ^– had no effect whereas SCN^– induced a small but significant increase in taurine influx. Taurine uptake was Na⁺-dependent under conditions where Cl^– had been replaced with NO ₃ ^– . However, it is apparent that the Na⁺-dependent taurine transport system requires the presence of a permeable anion because replacing Cl^– with gluconate markedly reduced taurine uptake. Cell-swelling, induced by a hyposmotic challenge, increased the efflux of taurine from gerbil mammary tissue via a pathway sensitive to niflumic acid.Abbreviations Tris (Tris(hydroxymethyl)aminomethane - BES (N,N-bis[2-hydroxyethyl]-2-aminoethane sulphonic acid)     

Both taurine and albumin support mouse sperm motility and fertilizing ability in vitro but there is no obligatory requirement for taurine

When mouse spermatozoa were washed immediately upon release from the epididymis, preincubated for up to 120 min in PVA-containing, albumin-free medium and assessed for their ability to fertilize cumulus-intact eggs in vitro, they were poorly fertile in comparison with their unwashed counterparts in the same medium. Fertilizing ability could be significantly improved by introducing taurine or albumin or by washing a second time at the end of preincubation. The most effective treatment was provided by the continuous presence of low concentrations (0.05-0.1 mg/ml) of BSA, similar to the amount of albumin detected in the supernatants removed during washing. There was no evidence that acrosome loss was inhibited by washing; rather, it was enhanced by the removal of a surface component which inhibits the acrosome reaction. The presence of taurine did not further increase this response. Motility, reduced in washed suspensions, was improved by the presence of taurine or albumin and experimental results suggest that this was a major factor in the improvement of fertilizing ability after introduction of these compounds. Although taurine, hypotaurine and albumin were all found in the sperm washings and thus would be present in unwashed, fertile samples, low concentrations of albumin were able to maintain full fertilizing ability. Therefore, unlike hamster spermatozoa, mouse spermatozoa would not appear to have an obligatory requirement for a motility stimulating factor such as taurine.     

Glial uptake system of GABA distinct from that of taurine in the bullfrog sympathetic ganglia

The kinetics and specificity of GABA and taurine uptake were studied in the bullfrog sympathetic ganglia. GABA uptake system consisted of simple saturable component and taurine uptake system consisted of two saturable components exclusive of non-saturable influx. Taurine unaffected GABA uptake while GABA inhibited taurine uptake competitively with theK _i/K_m ratio of 38. GABA (5.14 M) uptake was inhibited by -aminovaleric acid and slightly by 2,4-diaminobutyric acid (5 mM, each) among ten structural analogs. Taurine uptake under high-affinity conditions was most strongly suppressed by hypotaurine and -alanine competitively with theK _i/K_m ratio of 1.0 and 1.9, respectively. Autoradiography showed that glial cells were heavily labeled by both [³H]GABA and [³H]taurine. These results suggest that GABA is transported by a highly specific carrier system distinct from the taurine carrier and that taurine, hypotaurine, and -alanine may share the same high-affinity carrier system in the glial cells of the bullfrog sympathetic ganglia.     

Effects of taurine on the motility and intracellular free Ca2+ concentration of fowl spermatozoa in vitro

The effects of taurine on the motility and intracellular free Ca2+ concentration of fowl spermatozoa were investigated in vitro. The addition of taurine, within the range of 0-5 mmol l(-1), did not appreciably affect the motility of intact fowl spermatozoa. Motility remained almost negligible at 40 degrees C, while vigorous movement was observed at 25 degrees C. Even with the addition of Ca2+ before the addition of taurine, neither stimulation nor inhibition of motility was observed compared with the control (no addition of taurine). Similar results were obtained by the addition of taurine and calyculin A, a specific inhibitor of protein phosphatases. There were no changes in intracellular free Ca2+ concentrations, measured by a fluorescent Ca2+ indicator, fura-2, in taurine-treated spermatozoa. These results suggest that taurine is not involved in the regulation of fowl sperm motility and metabolism by intracellular Ca2+ mobilization in vitro.     

Taurine-induced long-lasting potentiation in the rat hippocampus shows a partial dissociation from total hippocampal taurine content and independence from activation of known taurine transporters

Perfusion with high millimolar levels of taurine evoked a long-lasting potentiation (LLP-TAU) of synaptic transmission in the Schaffer-collateral CA1 region of the rat hippocampus. Although LLP-TAU showed some correlations to increases in the total taurine content of hippocampal slices, it could not be blocked by the taurine transport inhibitor guanidinoethanesulfonic acid (GES), which was able to significantly reduce total slice taurine uptake. Inhibition of GABA transport by either nipecotic acid or beta-guanidinopropionate failed to abolish LLP-TAU and had no significant effect on taurine uptake. The combination of GES and nipecotic acid also had no significant effect on LLP-TAU. Experiments with transportable structural analogs of taurine (beta-aminoisobutyric acid, homotaurine, and isethionic acid) suggest that activation of classical taurine transport pathways does not always yield a robust LLP-TAU. Hippocampal LLP-TAU could be significantly attenuated, however, by pre-incubation with submillimolar levels of taurine. In summary, the development of LLP-TAU in the rat hippocampus appears to be associated with the intracellular accumulation rather than the activation of known transporters of taurine, but the precise means of its accumulation remains to be identified.     

Net taurine transport and its inhibition by a taurine antagonist

P₂-fractions were isolated from rat brain, and used to study net taurine transport. The fractions were incubated in increasing concentrations of [³H]taurine and the intraterminal concentration measured by liquid scintillation and amino acid analysis. The membrane potential of the isolated fractions was estimated using⁸⁶Rb⁺ as a marker for intracellular K⁺. Taurine was synthesized in the P₂-fraction when incubated in taurine free medium. At external taurine concentrations below 370 M a significant amount of the endogenous taurine was released to the incubation medium. Net taurine uptake into the P₂-fraction was achieved at external taurine concentrations exceeding 370 M. The taurine antagonist 6-aminomethyl-3-methyl-4H, 1, 2, 4-benzothiadiazine-1, 1-dioxide (TAG) competitively inhibited taurine and [³H]taurine transport into the P₂-fraction. As the external concentration of taurine was increased, the accumulation of⁸⁶Rb⁺ into the P₂-fraction was facilitated. This indicated an increasing hyperpolarization of the neuronal membrane as taurine transport shifted from release towards uptake. TAG reduced the hyperpolarization that paralleled taurine accumulation, in a dose dependent manner. Our results indicate that relatively low transmembranal gradients of taurine may be maintained by an electrogenic taurine transporter having a large transport capacity. Such a transporter may well serve the needs of osmotic regulation, i.e. to transport large amounts of taurine in any direction across the neuronal membrane.     

自发性高血压大鼠心肌和血管组织牛磺酸的转运障碍

在自发性高血压大鼠（SHR）的心肌和主动脉血管组织上观察牛磺酸（taurine)转运和牛磺酸转运体（taurine transporter,TAUT) mRNA 的改变,结果显示,与对照组WKY大鼠相比,SHR组血浆牛磺酸水平和牛磺酸释放量增加,而心肌和血管组织牛磺酸水平和TAUT mRNA含量均降低,牛磺酸最大转运速率（Vmax)分别低24％和35％（P＜0．05）,米氏常数（Km)值分别高16％和39％（P＜0．05）,这些结果提示,SHR的心肌和血管组织牛磺酸转运障碍可能与TAUT活性和亲和力降低及TAUT基因水平的下调有关。     

Effect of various extenders and taurine on survival of stallion sperm cooled to 5 degrees C

Stallion semen was diluted in five different extenders (dimitro-poulus onze (Dimitro's), Kenney's modified tryode (Kenney's), modified INRA82 (INRA82), egg yolk-citrate-taurine (Citrate) and EZ-Mixin) and evaluated for motility after cooling and storage at 5 degrees C for 0, 24, 48, 72 and 96 h. EZ-Mixin extender was used as control while 70 and 100 mM of taurine were added to Dimitro's, Kenney's and INRA82 to study its effect under conditions of storage at 5 degrees C and varying processing modifications. Motility in INRA82 was 57.0, 58.4, 61.1, and 56.1% after 24, 48, 72 and 96 h, respectively and was higher (P < 0.05) than in other extenders after 48, 72, and 96 h. Motility decreased over time in Dimitro's (P < 0.05) and Kenney's (P < 0.01). Motility in INRA82 and EZ-Mixin decreased (P < 0.05) after 24 h and then remained unchanged until 96 h. In taurine (70 mM) containing extender Citrate, motility decreased throughout storage. Motility in INRA82 and Kenney's with taurine decreased (P < 0.05 and P < 0.01, respectively) after 48 h, and then remained stable until 96 h only in INRA82 with taurine. Motility in INRA82 with taurine was higher (P < 0.05) than in Citrate throughout incubation, whereas motility in INRA82 with taurine was higher than in EZ-Mixin and Kenney's with taurine after 24 and 48 h, respectively. Motility in INRA82 and Kenney's with taurine improved (P < 0.05) when osmotic pressure was increased with taurine (100 mM) but not when osmotic pressure was increased with Na (+) and K (+) salts. Motility was always higher (P < 0.01) in taurine (70 mM or 100 mM) containing extenders than in non-taurine extenders, Dimitro's, INRA82, and Kenney's, when sperm were incubated for 24 h at 5 degrees C in these extenders, then washed and incubated at 39 degrees C in Sp-TALP for 12 or 24 h. In conclusion 1) INRA82 was a better extender than the other extenders tested. 2) inclusion of taurine (100 mM) in INRA82 and Kenney's improved sperm survival until 96 and 48 h, respectively, and 3) sperm preincubation for 24 h in taurine containing extenders resulted in better sperm survival when washed and stored in Sp-TALP for further 12 or 24 h.     

Urinary excretion of taurine in epilepsy

Evidence that taurine (2-aminoethanesulfonic acid) is related to the epilepsies is supported by work with both experimental animals and hurmans. It may function as a neurotransmitter or modulator of neurotransmission. Investigators using an automated amino acid analyzer reported lower mean urinary taurine excretion among epileptics. However, Rao et al. reported higher taurine excretion among epileptics using an older method. Analyses of the same epileptic and control urines by both methods coupled with paper and molecular size chromatography indicate that substances in addition to taurine are co-eluted with taurine using the older method, yielding spuriously high values. The resolution of this disparity is important because the urinary excretion of taurine may reflect primarily the influence of taurine transport alleles which may be polygenic components in the idiopathic epilepsies.     

Characteristics of taurine transport in rat hepatocytes in primary culture

Characteristics of taurine transport in rat hepatocytes maintained in primary culture for 24 h (cultured hepatocytes) have been investigated. The uptake of [3H] taurine by cultured hepatocytes at 2 degrees C was unsaturable, whereas that at 37 degrees C consisted of unsaturable and saturable processes. The saturable transport system was sodium-dependent and consisted of two processes with low and with high affinities. The latter process (Km, 76.9 microM; Vmax, 0.256 nmole/mg protein/min; activation energy (EA), 37.8 kcal mol-1) was competitively inhibited by 2,4-dinitrophenol and ouabain, as well as by taurine analogues such as hypotaurine and guanidinoethyl sulphonate. The Vmax and EA values found in cultured hepatocytes at 37 degrees C were 6.0 and 6.8 times higher than those found in freshly isolated hepatocytes. These results indicate that taurine transport in hepatocytes in primary culture consisted of unsaturable, and saturable, sodium and energy-dependent carrier-mediated transport processes, respectively. The facilitation of the latter transport system by primary culture of hepatocytes is also suggested.     

Analysis of hyposmolarity-induced taurine efflux pathways in the bullfrog sympathetic ganglia.

Hyposmolarity-induced taurine release was dependent on the decrease in medium osmolarity (5-50%) in the satellite glial cells of the bullfrog sympathetic ganglia. Release of GABA induced by hyposmolarity was much less than that of taurine. Omission of external Cl- replaced with gluconate totally suppressed taurine release, but only slightly suppressed GABA release. Bumetanide and furosemide, blockers of the Na+/K+/2Cl- cotransport system, inhibited taurine release by about 40%. Removal of external Na+ by replacement with choline, or omission of K+, suppressed taurine release by 40%. Antagonists of the Cl-/HCO3 exchange system, SITS, DIDS and niflumic acid, significantly reduced taurine release. The carbonic anhydrase inhibitor, acetazolamide, reduced the taurine release by 34%. Omission of external HCO3 by replacement with HEPES caused a 40% increase in the hyposmolarity-induced taurine release. Hyposmolarity-induced GABA release was not affected by bumetanide or SITS. Chloride channel blockers, 5-nitro-2-(3-phenylpropylamino) benzoic acid (NPPB) and N-phenylanthranilic acid (DPC), practically abolished taurine release. Blockers of K+ channels, clofilium and quinidine, had no effect on the taurine release. The hyposmolarity-induced taurine release was considerably enhanced by a simultaneous increase in external K+. GABA was not mediated by the same transport pathway as that of taurine. These results indicate that Cl- channels may be responsible for the hyposmolarity-induced taurine release, and that Na+/K+/2Cl- cotransporter and Cl-/HCO3 exchanger may contribute to maintain the intracellular Cl- levels higher than those predicted for a passive thermodynamic distribution in the hyposmolarity-induced taurine release.     

Effects of taurine on male reproduction in rats of different ages

Background

It has been demonstrated that taurine is one of the most abundant free amino acids in the male reproductive system, and can be biosynthesized by male reproductive organs. But the effect of taurine on male reproduction is poorly understood.

Methods

Taurine and β-alanine (taurine transport inhibitor) were offered in water to male rats of different ages. The effects of taurine on reproductive hormones, testis marker enzymes, antioxidative ability and sperm quality were investigated.

Results

The levels of T and LH were obviously increased by taurine supplementation in rats of different ages, and the level of E was also significantly elevated in baby rats. The levels of SOD, ACP, SDH and NOS were obviously increased by taurine administration in adult rats, but the levels of AKP, AST, ALT and NO were significantly decreased. The levels of SOD, ACP, LDH, SDH, NOS, NO and GSH were significantly elevated by taurine administration in aged rats, but the levels of AST and ALT were significantly decreased. The motility of spermatozoa was obviously increased by taurine supplement in adult rats. The numbers and motility of spermatozoa, the rate of live spermatozoa were significantly increased by taurine supplement in aged rats.

Conclusions

The present study demonstrated that a taurine supplement could stimulate the secretion of LH and T, increase the levels of testicular marker enzymes, elevate testicular antioxidation and improve sperm quality. The results imply that taurine plays important roles in male reproduction especially in aged animals.

     

Cell volume regulation in the perfused liver of a freshwater air-breathing catfishClarias batrachus under aniso-osmotic conditions: Roles of inorganic ions and taurine

The roles of various inorganic ions and taurine, an organic osmolyte, in cell volume regulation were investigated in the perfused liver of a freshwater air-breathing catfishClarias batrachus under aniso-osmotic conditions. There was a transient increase and decrease of liver cell volume following hypotonic (-80 mOsmol/l) and hypertonic (+80 mOsmol/l) exposures, respectively, which gradually decreased/increased near to the control level due to release/ uptake of water within a period of 25–30 min. Liver volume decrease was accompanied by enhanced efflux of K⁺ (9.45 ± 0.54 μmol/g liver) due to activation of Ba²⁺- and quinidine-sensitive K⁺ channel, and to a lesser extent due to enhanced efflux of Cl^- (4.35 ± 0.25 μmol/g liver) and Na⁺ (3.68 ± 0.37 μmol/g liver). Conversely, upon hypertonic exposure, there was amiloride- and ouabain-sensitive uptake of K⁺(9.78 ± 0.65 μmol/g liver), and also Cl^- (3.72 ± 0.25 μmol/g liver). The alkalization/acidification of the liver effluents under hypo-/hypertonicity was mainly due to movement of various ions during volume regulatory processes. Taurine, an important organic osmolyte, appears also to play a very important role in hepatocyte cell volume regulation in the walking catfish as evidenced by the fact that hypo- and hyper-osmolarity caused transient efflux (5.68 ± 0.38 μmol/g liver) and uptake (6.38 ± 0.45 μmol/g liver) of taurine, respectively. The taurine efflux was sensitive to 4,4′-di-isothiocyanatostilbene-2,2′-disulphonic acid (DIDS, an anion channel blocker), but the uptake was insensitive to DIDS, thus indicating that the release and uptake of taurine during volume regulatory processes are unidirectional. Although the liver of walking catfish possesses the RVD and RVI mechanisms, it is to be noted that liver cells remain partly swollen and shrunken during anisotonic exposures, thereby possibly causing various volume-sensitive metabolic changes in the liver as reported earlier.     

GABA and taurine sensitivity of cockroach giant interneurone synapses: Indirect evidence for the existence of a GABA uptake mechanism

The effects of exogenous GABA and taurine were studied on the cercal afferent-giant interneurone synapses (G.I. 2) located in the neuropile of the sixth abdominal ganglion of the cockroach, Periplaneta americana L. The decrease in excitatory synaptic potentials and the increase in postsynaptic membrane conductance due to GABA were enhanced by lowering the temperature of the saline, by using Na⁺ pump inhibitors, Na⁺ free salines or by agents blocking GABA uptake. The action of temperature was studied for taurine. Implications of these results for the identification of a metabolically dependent GABA uptake mechanism into glial cells are discussed.     

牛磺酸对学习记忆影响的研究现状

牛磺酸作为一种条件必须氨基酸对学习记忆能力的影响受到越来越多的关注,许多研究证明适量牛磺酸的添加可明显提高大鼠的记忆能力。通过牛磺酸对神经细胞、基因、激素、离子、受体、酶类等的作用,对其影响学习记忆方面的研究现状作出综述。