Immunocytochemistry of Amino-Acids in the Rodent Pituitary Using Extremely Specific, Very High Titre Antisera

The compartmental interrelationships of the metabolically related amino-acids glutamate, GABA and glutamine and the metabolically unrelated amino-acids taurine and glycine in the rodent pituitary, were investigated by light microscopic immunocytochemistry using highly specific antisera. Glutamate-like immunoreactivity was abundant in astrocytes in the posterior pituitary. Glutamine immunoreactivity was present only at low levels in the posterior pituitary, but was abundant in astrocytes within the intermediate lobe. Other glia-like ceils in the anterior pituitary were also glutamine-immunoreactive. GABA immunoreactivity was abundant in the intermediate lobe but absent from anterior and posterior lobes. The GABA immunoreactivity mainly took the form of small punctata, the majority of which were in intimate apposition to the glutamine-immunoreactive glia. Strong taurine immunoreactivity was present in astrocytes in the posterior pituitary but only weak labelling was present in intermediate and anterior lobes of the pituitary. Specific glycine immunoreactivity was not detected in the pituitary. These results suggest that glutamate-immunoreactive astrocytes in the posterior pituitary, unlike glia in loci such as the retina, do not convert much, if any, of their glutamate content into glutamine (or if they do, it is rapidly further metabolized to another compound), whereas those astrocytes in the intermediate lobe do contain glutamine. The spatial association of GABAergic fibres with glutamine-positive astrocytes raises the possibility that astrocytes in the intermediate lobe receive a GABAergic innervation. Glutamate, glutamine and taurine (or their metabolites) may have roles as neuroactive substances regulating pituitary secretion.     

gamma-Aminobutyric acid and taurine release in the striatum of the rat during hypoglycemic coma, studied by microdialysis

Extracellular levels of striatal gamma-aminobutyric acid (GABA) and taurine were monitored during insulin-induced hypoglycemia using microdialysis. At the onset of isoelectricity in the electroencephalogram (EEG), a transient 5-fold increase in the levels of GABA occurred. Taurine levels increased 5 min following the onset of isoelectricity and continued to increase during the entire isoelectric period. The results demonstrate that events associated with the onset of isoelectricity during hypoglycemia trigger an increase in extracellular concentrations of GABA and taurine. The discrepancy in time-course of these changes may reflect differences in compartmentation, function and metabolism of the two amino acids.     

Imaging and retention measurements of selenium 75 homocholic acid conjugated with taurine,and the carbon 14 glycochol breath test to document ileal dysfunction due to late radiation damage

In order to assess ileal dysfunction in patients with complaints after pelvic radiation therapy, retention measurements and scintigraphic imaging with selenium 75 homocholic acid conjugated with taurine (⁷⁵Se-HCAT), combined with the carbon 14 glycochol breath test, were evaluated in 39 patients. In 22 patients without ileal resection the results of the⁷⁵Se-HCAT test and the breath test differentiated between a normal functioning ileum (both tests negative) and ileal dysfunction as a cause of complaints (one or both tests positive). Among the patients with ileal dysfunction, the combination of both tests permitted those with bacterial overgrowth (breath test positive,⁷⁵Se-HCAT negative) to be separated from patients with evidence of bile acid malabsorption (⁷⁵Se-HCAT positive, breath test positive or negative). In 17 patients with small-bowel resection, the⁷⁵Se-HCAT test helped to estimate the severity of bile acid malabsorption with implications for therapy. In this group the breath test was false-negative in 7 cases with abnormal⁷⁵Se-HCAT. Additional systematically performed scintigraphic imaging improved the accuracy of the⁷⁵Se-HCAT test, revealing cases with prolonged colonic accumulation of the radiopharmaceutical, causing spurious retention values. In conclusion, assessment of ileal dysfunction by nuclear medicine techniques in post-irradiation conditions provides information about the aetiology and therefore the possibility of adjustment in the clinical management. Offprint requests to: R.A. Valdes Olmos     

牛磺酸含量与实验性白内障关系的研究

以实验性半乳糖性白内障大鼠血、房水、晶体中牛磺酸含量的变化研究了牛磺酸与白内障发病的关系。结果半乳糖性白内障大鼠血中牛磺酸含量在发病晚期明显下降。实验组较正常组减少６８．１７％；房水中牛磺酸含量第５，８，１４天分别下降４１．０２％，４８．３０％，５４．８０％；晶体牛磺酸含量第５，８，１４天分别下降７６．９１％，７４．８４％，８５．１３％。作者认为半乳糖性白内障的发病与机体血、房水、晶体中牛磺酸含量的减少有密切关系，且在白内障发病初期眼局部牛磺酸含量的减少尤为明显。     

牛磺酸对苯并芘体外诱导血小板聚集活化功能的影响

取健康志愿者外周静脉血并分离血小板,采用随机分组的方式将血小板分成6组。通过检测血小板最大聚集率、膜表面CD62P及PAC-1阳性表达率,探讨不同浓度的牛磺酸(Tau)对苯并芘(BAP)体外诱导血小板聚集活化功能的影响。结果表明,血小板最大聚集率在二磷酸腺苷( ADP)和胶原诱导下各浓度BAP-Tau组与溶剂对照组之间比较差异均有统计学意义(P<0．01)。血小板膜表面CD62P、PAC-1表达率BAP-Tau高浓度组与溶剂对照组比较差异有统计学意义(P<0．01)。不同浓度的Tau均可拮抗BAP致血小板功能损伤的作用,且呈浓度梯度性变化。     

Changes in brain amino acid content induced by hyposmolar stress and energy deprivation

The changes in endogenous amino acids in brain extracellular and intracellular compartments evoked by hyposmotic stress and energy deprivation were compared. Tissue content and release of ten amino acids were measured simultaneously in rat hippocampal slices by means of high performance liquid chromatography Hyposmotic stress induced a large release of taurine (25568 pmol mg-7 protein), and a smaller release of glutamate, accompanied by an inverse change in tissue content. Adding mannitol to correct osmolarity blocked these changes. Energy deprivation caused an increase in the release of all amino acids except glutamine. The release was particularly large for glutamate and GABA (31141 and 13282 pmol mg^–1 respectively). The intracellular concentrations were generally reduced, but the total amount of the released amino acids increased. In contrast to the effect seen during hyposmolar stress, mannitol enhanced the changes due to energy deprivation. The results show that hyposmolar stress and energy deprivation cause different content and release profiles, suggesting that the mechanisms involved in the two situations are either different, or modulated in different ways. The intracellular amino acid depletion seen during energy deprivation shows that increased outward transport is probably a primary eventL, and increased amino acid formation likely secondary to this release. [Neurol Res 1995; 17: 402–408]     

Oral administration of taurine improves experimental pancreatic fibrosis

Background and Aim: The mechanism of pancreatic fibrosis is unclear. Taurine is used in the clinical treatment of a wide variety of diseases, but its effect on improving pancreatic fibrosis is unknown. We examined whether a diet with added taurine improves pancreatic fibrosis induced by dibutyltin dichloride (DBTC) in an experimental chronic pancreatitis rat model. In addition, we examined the influence of taurine on pancreatic stellate cells. Methods: Pancreatic fibrosis was induced by DBTC. Rats were fed a taurine‐containing diet or a normal diet and were killed at 4 weeks. Pancreatic stellate cells were isolated from male Wistar rats. Cultured pancreatic stellate cells were incubated with or without taurine chloramine. Type I collagen and transforming growth factor‐β1 secretion was evaluated by ELISA, and matrix metalloproteinase activity was assessed by gelatin zymography. Interleukin‐6, interleukin‐2, and transforming growth factor‐β1 levels in the supernatants of pancreatic tissue homogenates were measured. Results: Pancreatic fibrosis induced by DBTC was improved remarkably by the oral administration of the taurine‐containing diet. Taurine chloramine decreased type I collagen, transforming growth factor‐β1, and matrix metalloproteinases 2 of the pancreatic stellate cell culture supernatant. Increased interleukin‐6 and decreased interleukin‐2 were found in the supernatants of the pancreatic tissue homogenates of DBTC‐induced pancreatitis rats compared with other groups. Conclusion: The oral administration of taurine improves pancreatic fibrosis. Taurine chloramine inhibits transforming growth factor‐β1 produced from activated pancreatic stellate cells and improves pancreatic fibrosis.     

Differential effect of taurine and serotonin on the outgrowth from explants or isolated cells of the retina

The sulfur amino acid taurine and the indoleamine serotonin increases and decreases, respectively, the outgrowth from goldfish retinal explants. Taurine seems to be acting, at least partially, through an increase in calcium fluxes, and the serotonin-inhibiting effect appears to be mediated by serotonin_1A receptors and cAMP. Isolated cells of postcrush goldfish retina and of retina from 5-day-old rats were cultured in the presence of taurine or serotonin. In the goldfish, the classical morphology of postcrush ganglion cells was observed. An antibody against the glycoprotein Thy-1 labelled three types of cells in the cultures of goldfish retina. The number of cells outgrowing and the length of the main neurite was measured at 5 days in culture in both species. The number of cells presenting neurites was increased in the goldfish retina by the addition of taurine, and decreased by serotonin. However, the length of the neurites was unaffected by the addition of the modulators. In the rat, only a slight decrease in the number of cells outgrowing was observed in the presence of serotonin. The incorporation of [³H]thymidinewas not modified after 5 days in culture in the presence of taurine or serotonin, either in the goldfish or in the rat retina. The antibody Thy 1.1 can label retinal cells of the goldfish invitro, one of them being ganglion cells. The trophic effect exerted by taurine in the postcrush goldfish retina needs the integrity of the tissue favoring the interaction of cells and factors, because outgrowth increases in retinal explants, but not in isolated cells.