Heterogeneity of Na+/K+-ATPase from rectal gland of Squalus acanthias is not due to α isoform diversity

 Purified Na⁺/K⁺-ATPase (EC 3.6.1.37) isolated from the rectal gland of Squalus acanthias was characterized in ouabain-binding studies and with respect to isoform(s) of the α peptide. To avoid enzyme inactivation [³H]ouabain equilibrium binding was carried out at 20°C. The heterogeneity of Na⁺/K⁺-ATPase isolated from shark rectal gland was similar in [³H]ouabain binding as previously seen in hydrolytic studies. The binding isotherms were compatible with the existence of a high-affinity (K _dis 0.69 nM) and a low-affinity (K _dis 42 nM) component of 1.46 and 0.79 nmol^.(mg protein)^–1, respectively. In Western blots the α peptide of the enzyme hybridized with an isoform-specific polyclonal antibody raised to an α₃-specific region of the large intracellular domain of rat Na⁺/K⁺-ATPase, but not with the supposed α₃-specific monoclonal antibody MA3-915 with its epitope near the N-terminus. Semi-quantitative analysis of the reaction of the α₃-specific polyclonal antibody with the α peptide from the shark enzyme compared to the reaction with α peptide from rat brain enzyme indicated that this region is not exactly the same in the two species. The α peptide of shark enzyme was not recognized by α₁- or α₂-specific polyclonal antibodies, or by the α₁-specific monoclonal antibodies 3B and F6. The large intracellular domain of Na⁺/K⁺-ATPase from shark rectal gland thus seems to be α₃-like and no α isoform heterogeneity seems able to account for the heterogeneity seen in ouabain binding. Received: 7 August 1998 / Accepted: 6 November 1998     

Cytoskeleton mediates inhibition of the fast Na+ current in respiratory brainstem neurons during hypoxia

Whole-cell Na+ currents (INa) were recorded in inspiratory neurons in a medullary slice preparation from neonatal mouse that contains the functional respiratory network. Hypoxia and metabolic poisoning with KCN rapidly inhibited INa by reducing the number of Na+ channels available for opening during depolarization. Application of agents specific for G-proteins, protein kinase C and A, intracellular Ca2+ and pH did not prevent the hypoxic inhibition of INa. The effects of hypo-osmolarity and hypoxia were additive, whereas hyperosmolarity partially prevented a subsequent hypoxic inhibition of INa. Cytochalasin B and colchicine decreased, and taxol or phalloidin increased INa and reduced its hypoxic inhibition. We conclude that cytoskeleton rearrangements during hypoxia are responsible for suppression of a fast INa in brainstem respiratory neurons, which could be mediated by the uncoupling of channel inactivation gates from cytoskeletal elements.     

Inhibition of Ca2+ transport associated with cAMP-dependent protein phosphorylation in rat cardiac sarcoplasmic reticulum by triorganotins

Organotin compounds have been shown to interfere with cardiovascular system. We have studied the in vitro and in vivo effects of tributyltin bromide (TBT), triethyltin bromide (TET) and trimethyltin chloride (TMT) on the cardiac SR Ca²⁺ pump, as well as on protein phosphorylation of SR proteins, in order to understand the relative potency of these tin compounds. All the three tin compounds inhibited cardiac SR⁴⁵Ca uptake and Ca²⁺-ATPase in vitro in a concentration-dependent manner. The order of potency for Ca²⁺-ATPase as determined by IC₅₀, is TBT (2 M) > TET (63 M) > TMT (280 M). For⁴⁵Ca uptake, it followed the same order i.e., TBT (0.35 M) > TET (10 M) > TMT (440 M). In agreement with the in vitro results, both SR Ca²⁺-ATPase and⁴⁵Ca uptake were significantly inhibited in rats treated with these tin compounds, indicating that these tin compounds inhibit cardiac SR Ca²⁺ transport. cAMP significantly elevated (70–80%) the³²P-binding to SR proteins in vitro in the absence of any organotin. In the presence of organotins, cAMP-stimulated³²P-binding to proteins was significantly reduced, but the decrease was concentration dependent only at lower concentrations. The order of potency is TBT > TET > TMT. In agreement with in vitro studies, cAMP-dependent³²P bound to proteins was significantly reduced in rats treated with TBT, TET and TMT. SDS-polyacrylamide gel electrophoresis of the cardiac SR revealed at least 30 Coomassie blue stainable bands ranging from 9 to 120 kDa. Autoradiographs from samples incubated in the presence of cAMP indicated³²P incorporation in seven bands. Of these, the band corresponding to about 24 kDa molecular weight protein decreased in its intensity with the treatment of organotins. These results suggest that triorganotins may be affecting Ca²⁺ pumping mechanisms through the alteration of phosphorylation of specific proteins in rat cardiac SR.This work has been presented in part at the Annual meeting of Society of Toxicology, 1990 at Miami Beach, FL. The Toxicologist 10: 35 & 108 (1990).     

氟罗沙星葡萄糖注射液处方工艺改进

目的　制备符合注射剂质量要求的 2 g· L-1氟罗沙星葡萄糖注射液。方法　去掉原处方中作为抗氧剂的维生素 C,而加入 0 .0 5 g·L-1EDTA- 2 Na作为金属离子络合剂 ;原处方中含量为 2 7.5 g· L-1的葡萄糖调整为 5 0 g· L-1。结果　改进后的 2 g· L-1氟罗沙星葡萄糖注射液质量符合要求。结论　改进后的处方合理 ,制备工艺简单 ,质量稳定。临床用药安全、有效     

Isoform-specific effects of a novel BmK 11(2) peptide toxin on Na channels.

BmK 11(2) is a 7216Da polypeptide toxin purified from the venom of the scorpion Buthus martensii Karsch. Nanomolar concentrations of the toxin prolong amphibian nerve action potentials without attenuation of the amplitude. The pharmacological action of the toxin and its sequence similarity to other alpha-scorpion toxins suggest that BmK 11(2) selectively alters voltage-gated Na channels. In order to test whether BmK 11(2) preferentially modulates the gating or kinetics of certain channel isoforms, we applied BmK 11(2) to muscle, heart and neuronal Na channels. 100nM BmK 11(2) increased the peak current amplitude of skeletal muscle (micro1) and neuronal (N1E-115) Na currents by 40 and 20%, respectively, and reduced the cardiac Na (hH1) current by 15%. The toxin slowed current decay of all isoforms, most prominently in N1E-115 (tau(BmK)/tau(Control)=12), micro1 (11), and less so for hH1 (1.3). BmK 11(2) shifted the voltage dependence of activation of micro1 and N1E-115 currents. BmK 11(2) had no effect on steady-state inactivation, use-dependent availability, and the kinetics of entry into slowly recovering inactivated states.     

胆红素对神经突触膜Na^＋,K^＋—ATP酶影响的实验研究

为了研究胆红素的神经毒性作用，对５９只出生２天的ＳＤ大白鼠分别予以腹腔注射不同剂量胆红素制造高胆红素血症动物模型，不连续密度梯度法分离提取脑神经元突触膜，测定Ｎａ＋，Ｋ＋－ＡＴＰ酶活力。结果：随着血清胆红素浓度的逐渐增加，脑组织中胆红素沉积量也逐渐增加，神经元突触膜Ｎａ＋，Ｋ＋－ＡＴＰ酶活力逐渐降低，Ｎａ＋，Ｋ＋－ＡＴＰ酶活力与脑组织中沉积的胆红素量呈负相关（ｒ＝－０．３４，Ｐ＜０．０１）。提示：胆红素对Ｎａ＋，Ｋ＋－ＡＴＰ酶具有抑制作用。     

仙芦抗癌胶囊抗肿瘤作用及对肝癌HepG2细胞内Ca2+浓度的影响

目的观察仙芦抗癌胶囊的体内外抗肿瘤作用及对人肝癌HepG2细胞内Ca2 浓度([Ca2 ]i)的影响,从而揭示仙芦抗癌胶囊的抗肿瘤作用机制。方法通过观察仙芦抗癌胶囊对S180A荷瘤小鼠瘤质量和H22小鼠生存时间的影响,观察其体内抗肿瘤作用。通过MTT法观察含药血清对肝癌HepG2细胞的细胞毒作用。通过Fluo-3/AM标记HepG2肝癌细胞,激光共聚焦扫描显微术测定肿瘤细胞[Ca2 ]i,ATP酶试剂盒测定HepG2细胞膜Ca2 ,Mg2 -ATP酶活性。结果仙芦抗癌胶囊(1.00、0.50、0.25g/kg)对S180A小鼠的瘤体生长有显著的抑制作用,对H22小鼠的生存时间有显著的延长作用。仙芦抗癌胶囊体外对HepG2细胞有细胞毒作用;对细胞[Ca2 ]i有显著升高作用,高、中剂量(1.00、0.50g/kg)能够降低HepG2肝癌细胞膜Ca2 ,Mg2 -ATP酶活性。结论仙芦抗癌胶囊有明显的体内外抗肿瘤作用,其作用机制为抑制肿瘤细胞膜Ca2 ,Mg2 -ATP酶活性,增加细胞[Ca2 ]i,从而诱导肿瘤细胞凋亡,达到抗肿瘤作用的目的。     

兔眼外伤性前部PVR睫状体Na+,K+-ATP酶和碳酸酐酶活性改变

目的　研究外伤性前部PVR睫状体Na ,K ATP酶和碳酸酐酶活性变化 ,进一步探讨外伤性前部PVR导致慢性低眼压的机制。方法　制作外伤性前部PVR导致慢性低眼压兔眼模型 ,伤后分别于 2、4、8、16周测量眼压后取眼球 ,部分睫状体做普通病理切片 ,HE染色观察 ,部分睫状体做Na ,K ATP酶活性测定和碳酸酐酶组织化学观察。结果　伤后实验组Na ,K ATP酶活性下降 ,而对照组变化不很明显 ,2组间比较有显著性差异 ;实验眼睫状体上皮碳酸酐酶组织化学显色部分区域为浓棕黑色 ,表明这部分上皮碳酸酐酶活性接近正常水平 ,而上皮破坏区域 ,酶组织化学显色比较弱 ,接近于阴性对照睫状体上皮的颜色 ,为淡黄褐色 ,表明这部分上皮碳酸酐酶活性较低。结论　外伤性前部PVR睫状体Na ,K ATP酶和碳酸酐酶活性降低 ,是导致房水分泌减少及慢性低眼压的一个重要原因。     

长期使用敌鼠钠盐地区杀灭黄胸鼠的效果评价

目的评价长期使用敌鼠钠盐的地区敌鼠钠盐对黄胸鼠的毒杀效果。方法现场使用不同浓度毒饵进行7d饱和投药。结果0.10%和0.16%稻谷毒饵的盗食率分别为35.99%和26.21%,灭效分别为79.44%和92.70%。0.10%小麦毒饵的盗食率和灭效分别为38.36%和85.92%。2种稻谷毒饵的盗食率差异有显著性(χ2=12.97,P<0.01),灭效差异无显著性(χ2=0.32,P>0.05)。相同浓度的敌鼠钠盐稻谷和小麦毒饵之间盗食率和灭效差异均无显著性(χ2=0.64,P>0.05;χ2=0.03,P>0.05)。结论该地使用敌鼠钠盐防制黄胸鼠仍有良好效果,不宜盲目提高药物的使用浓度,但灭鼠药物的轮换使用应予以重视。