Noradrenaline transport by rat heart sympathetic nerves: A re-examination of the role of sodium ions

Summary The effect of sodium ion on ³H-(–)-noradrenaline (0.0875 to 0.5 M) transport by rat heart atrial hemi-appendages incubated in vitro has been studied, and the following observations made: a) When sodium was omitted (choline and lithium substitution) there was no evidence for active noradrenaline transport, and only a component that did not show saturation kinetics up to 1 M noradrenaline, remained. b) Omission of sodium or addition of 4×10^–5 M desipramine inhibited noradrenaline transport to exactly the same extent, and their effects were not additive. Alprenolol did not reduce this sodium-independent transport, but tropolone lowered it somewhat. c) No evidence for corticosterone-sensitive noradrenaline transport (uptake-2) was found in this preparation at the low amine concentrations used. d) In control medium, the kinetic parameters of transport were: K _m: 0.59 ± 0.063 M and V _max: 2.44 ± 0.43 (pmoles/mg protein/min). With 26 mM sodium and the rest substituted by choline, K _m:2.26 ± 0.70 M (P0.001) and V _max: 2.74 ± 0.43 (pmoles/mg protein/min) (not significant). Also with 26 mM sodium, but with sucrose substitution, K _m: 0.76 ± 0.13 M (N.S.) and V _max: 1.06 ± 0.13 (pmol/mg/min) (P<0.05). Such results indicate that sodium only modifies the affinity of the transport system for noradrenaline, without changing V _max, and that changes in the latter are only a consequence of a reduction of the ionic strength. e) When noradrenaline transport was studied at different concentrations of external sodium, at constant ionic strength and with precautions to minimize the noradrenaline-releasing effect of low sodium, it was found that the data could be best represented by two hyperbolas placed in series. This suggests that the noradrenaline carrier has two sites for sodium, that do not interact with each other. When the same experiments were repeated in the absence of chloride, it was found that the noradrenaline transport system had lost virtually all its affinity for sodium. f) The effect of prolonged tissue incubation in the absence of sodium was found to produce a relatively small inactivation of noradrenaline transport. Such phenomenon was enhanced by raising the calcium concentration to 2 mM.     

反相离子对高效液相色谱法测定泰必治注射液A中4种组分的含量

目的 :采用反相离子对高效液相色谱法测定泰必治注射液A中盐酸利多卡因、地塞米松、卡巴芬乙酸 (钠盐 )与保泰松钠 4种组分的含量。方法 :采用YWG -C1 8(10 μm ,4 5mm× 15 0mm)色谱柱 ,以乙腈 -水 (4 5∶5 5 ,含 2 5mmol·L- 1十六烷基三甲基溴化铵 )为流动相 ,流速 1 5mL·min- 1 ,柱温 40℃ ,检测波长 2 30nm。结果 :本法可同时测定 4种组分的含量。盐酸利多卡因在 13～ 6 4μg·mL- 1 、地塞米松在 4 5～ 38μg·mL- 1 、卡巴芬乙酸 (钠盐 )在 2 6 9～ 16 14μg·mL- 1 、保泰松钠在 40 2～ 2 0 77μg·mL- 1 范围内 ,峰面积与其浓度呈良好的线性关系 ;平均回收率 (n =5 )依次为 99 9% (RSD =1 2 % ) ,10 1 0 % (RSD =0 4% ) ,10 0 5 % (RSD =0 2 % ) ,10 0 6 % (RSD =0 8% )。结论 :方法简便、快速、准确 ,可作为样品的检测方法。     

Impaired receptor-mediated endocytosis by the asialoglycoprotein receptor in ethanol-fed mice: implications for studying the role of this receptor in alcoholic apoptosis

During receptor-mediated endocytosis (RME), extracellular molecules are internalized after being recognized and bound to specific cell surface receptors. In previous studies of the asialoglycoprotein receptor (ASGPR) in rats, we showed that ethanol impairs RME at multiple ASGPR sites. Ethanol administration has been shown to increase apoptosis, and we demonstrated increased sensitization to apoptotic induction in hepatocytes from ethanol-fed rats. Although a physiological role for the ASGPR has not been identified, investigators have shown its involvement in the uptake/clearance of apoptotic cells in vitro. This suggests a potential role for the ASGPR in the removal of apoptotic cells, and the recent availability of an ASGPR-deficient mouse strain provides an excellent opportunity to examine the role of the ASGPR during ethanol impairment. In this study, we examined ethanol-impaired RME in mice and began the characterization of ASGPR-deficient mice for use in ethanol studies. Similar to our findings with rats, ligand binding, internalization, and degradation were decreased 45-50% in hepatocytes from ethanol-fed wild-type mice. In ASGPR-deficient mice, these parameters did not vary among the chow-fed, pair-fed control, or ethanol groups and were negligible compared with those of wild-type mice. TUNEL analysis of liver sections showed an ethanol-induced increase in apoptotic bodies in all mouse strains with a significant difference in the receptor-deficient mice. Further, the livers of ASGPR-deficient mice had three times more apoptotic bodies, in all feeding groups, compared with wild-type mice. These results support the use of the ASGPR-deficient mouse model for studying ethanol-induced liver injury, specifically ethanol-induced apoptosis.