Table of Contents of Volume 52 - 2004

Table of Contents

Table of Contents of Volume 52 - 2004     

Adrenomedullin(27-52) inhibits vascular calcification in rats

Adrenomedullin (ADM) has the vasodilatory properties and involves in the pathogenesis of vascular calcification. ADM could be degraded into more than six fragments in the body, including ADM(27-52), and we suppose the degrading fragments from ADM do the same bioactivities as derived peptides from pro-adrenomedullin. The present study carries forward by assessing the effects on vascular calcification of the systemic administration of ADM(27-52). The rat vascular calcific model was replicated with vitamin D3 and nicotine. ADM or/and ADM(27-52) were systemically administrated with mini-osmotic pump beginning at seventh day after the model replication for 25 days. Vascular calcific nodules histomorphometry, vascular calcium content, vascular calcium uptake, alkaline phosphatase activity, and osteopontin-mRNA quantification in aorta were assessed. ADM limited 40.2% vascular calcific nodules (P<0.01), did not effect on calcium content (P>0.05), reduced 44.4% calcium uptake (P<0.01), lowered 21.1% alkaline phosphatase activity (P<0.01), and regulated 40.9% downwards osteopontin-mRNA expression (P<0.01) in the aorta of rats with vascular calcification. ADM(27-52) receded 32.0% vascular calcific nodules (P<0.01), taken from 55.5% calcium content (P<0.01), did not affect calcium uptake (P>0.05), inhibited 22.5% alkaline phosphatase activity (P<0.01), and restrained 21.9% osteopontin-mRNA expression (P<0.01) in the aorta of rats with vascular calcification. Both of ADM and ADM(27-52) did interact on vascular calcification each other. ADM could partially antagonize the effects of ADM(27-52) in taking from calcium content (17.5%, P<0.01) and in receding vascular calcific nodules (18.6%, P<0.01). ADM could obviously enhance the action of ADM(27-52) in inhibiting alkaline phosphatase activity (14.4%, P<0.01) and in reducing calcium uptake (11.4%, P<0.01). ADM(27-52) could partially antagonize the effects of ADM on regulating downwards osteopontin-mRNA expression (17.0%, P<0.01). It is concluded that ADM(27-52) derived from ADM acts as an inhibitory agent on vascular calcification, with special mechanisms different from ADM derived from ADM progenitor molecule.     

Intermolecular coupling between loop 38-52 and the C-terminus in actin filaments.

The recently reported structural connectivity in F-actin between the DNase I binding loop on actin (residues 38-52) and the C-terminus region was investigated by fluorescence and proteolytic digestion methods. The binding of copper to Cys-374 on F- but not G-actin quenched the fluorescence of dansyl ethylenediamine (DED) attached to Gin-41 by more than 50%. The blocking of copper binding to DED-actin by N-ethylmaleimide labeling of Cys-374 on actin abolished the fluorescence quenching. The quenching of DED-actin fluorescence was restored in copolymers (1:9) of N-ethylmaleimide-DED-actin with unlabeled actin. The quenching of DED-actin fluorescence by copper was also abolished in copolymers (1:4) of DED-actin and N-ethylmaleimide-actin. These results show intermolecular coupling between loop 38-52 and the C-terminus in F-actin. Consistent with this, the rate of subtilisin cleavage of actin at loop 38-52 was increased by the bound copper by more than 10-fold in F-actin but not in G-actin. Neither acto-myosin subfragment-1 (S1) ATPase activity nor the tryptic digestion of G-actin and F-actin at the Lys-61 and Lys-69 sites were affected by the bound copper. These observations suggest that copper binding to Cys-374 does not induce extensive changes in actin structure and that the perturbation of loop 38-52 environment results from changes in the intermolecular contacts in F-actin.     

肾上腺髓质素（13－52）降压机制的探讨

本工作在整体和离体大鼠模型上观察研究了肾上腺髓质素（１３－５２）［ＡｄＭ（１３－５２）］的降压机制,发现ＡｄＭ（１３－５２）的降压作用可被一氧化氮合酶（ＮＯＳ）的竟争性桔抗剂Ｌ－ＮＧ－硝基－精氨酸（ＬＮＮＡ）部分抑制;ＡｄＭ（１３－５２）的舒血管作用依赖于血管内皮并可被ＬＮＮＡ抑制,且具有剂量效应关系,ＬＮＮＡ的这种效应可被Ｌ－精氨酸（Ｌ－Ａｒｇ）逆转;用亚甲蓝（ＭＢ）阻断血管内的环－磷酸鸟苷酸（ｃＧＭＰ）,则导致ＡｄＭ（１３－５２）的舒血管作用消失;放免测定显示ＬＮＮＡ可以降低血管内ｃＧＭＰ含量,而ＡｄＭ（１３－５２）则使后者含量增加,这一现象在ＡｄＭ（１３－５２）与ＬＮＮＡ合用时消失。实验结果提示,ＡｄＭ（１３－５２）的舒血管降血压效应与ＮＯ有关,可能是通过ＮＯ介导的。