Peroxynitrite induces arteriolar smooth muscle cells membrane hyperpolarization with arteriolar hyporeactivity in rats

Peroxynitrite (ONOO-) has been recently known to act as a potent cytotoxin during pathogenesis of various diseases. This study aimed to investigate the possible effect of ONOO- on the cremaster muscle arteriolar reactivity in response to noradrenaline and subsequently determined whether membrane hyperpolarization and potassium channel activation were involved in ONOO(-)-induced alteration of arteriolar reactivity. The results demonstrated that 1) ONOO- could decrease arteriolar reactivity in a time- and concentration-dependent manner with no significant alteration of arteriolar diameter; 2) Superfusion with 20 microM ONOO- over 40 minutes showed slight but not significant influence on the resting potential (Em) of arteriolar smooth muscle cells (ASMCs). However, ASMCs subjected to 50 or 100 microM ONOO- administration were significantly hyperpolarized. As control, treatment with 50 microM decomposed ONOO- or Kreb's solution had little effect on the Em of ASMCs; 3) ONOO(-)-induced arteriolar hyporeactivity could be greatly reversed by co-administration of KCl and partially by TEA. The above results indicated that membrane hyperpolarization and potassium channel activation were preferentially responsible for the reduction of cremaster muscle arteriolar reactivity after exposure to ONOO-.     

微动脉平滑肌细胞K^＋通道的研究进展

K^＋通道维持着血管平滑肌细胞的静息膜电位。目前发现血管微动脉平滑肌细胞上主要表达内向整流型K^＋通道、ATP敏感型K^＋通道、电压依赖型K^＋通道和大电导钙激活型K^＋通道等四种K^＋通道。本文对微动脉平滑肌细胞K^＋通道最新进展做一综述。     

达格列净对高血压小鼠小动脉重构的影响及机制

摘要 目的：探究钠葡萄糖共转运蛋白2抑制剂（达格列净）对高血压小鼠小动脉重构的影响及机制。方法：30只12周龄的C57BL / 6雄性小鼠纳入本研究,根据实验目的将实验小鼠分为对照组、模型组和达格列净组。检测并比较各组小鼠心脏肥大、心脏纤维化、动脉重塑、炎症因子mRNA表达、PI3K和Akt蛋白质表达以及细胞活力和细胞迁移。结果：与对照组相比,模型组收缩压和心脏/体重增加（P<0.05）。与模型组相比,达格列净组收缩压和心脏/体重降低（P<0.05）。与对照组相比,模型组RV/（LV+S）和得分增加（P<0.05）。与模型组相比,达格列净组RV/（LV+S）和得分降低（P<0.05）。与对照组相比,模型组显示血管壁增厚,透明质改变,脑小动脉管腔狭窄或闭塞（P<0.05）。与模型组相比,达格列净组降低高血压引起的小动脉重塑（P<0.05）。与对照组相比,模型组IL-1β,IL-6和TNF-α的mRNA表达水平增加（P<0.05）。与模型组相比,达格列净组IL-1β,IL-6和TNF-α的mRNA表达水平降低（P<0.05）。与对照组相比,模型组PI3K和Akt蛋白质表达水平增加（P<0.05）。与模型组相比,达格列净组PI3K和Akt蛋白质表达水平降低（P<0.05）。与对照组相比,模型组VEZF1,Angpt-1和IGF1表达水平降低（P<0.05）。与模型组相比,达格列净组VEZF1,Angpt-1和IGF1表达水平增加（P<0.05）。与对照组相比,模型组细胞活力和细胞迁移降低（P<0.05）。与模型组相比,达格列净组细胞活力和细胞迁移增加（P<0.05）。结论：达格列净通过抑制PI3K / Akt信号通路,降低炎症反应,增加血管生成能力,降低高血压小鼠小动脉重构。     

Conformation and vasoreactivity of VIP in phospholipids: effects of calmodulin

The purpose of this study was to determine the conformation and vasorelaxant effects of vasoactive intestinal peptide (VIP) self-associated with sterically stabilized phospholipid micelles (SSM) and whether calmodulin modulates both of these processes. Circular dichroism spectroscopy revealed that VIP is unordered in aqueous solution at room temperature but assumes appreciable α helix conformation in SSM. This conformational transition was amplified at 37°C and by a low concentration of calmodulin (0.1 nM). Suffusion of VIP in SSM elicited significant time- and concentration-dependent potentiation of vasodilation relative to that elicited by aqueous VIP in the in situ hamster cheek pouch (P < 0.05). This response was significantly potentiated by calmodulin (0.1 nM). Collectively, these data indicate that exogenous calmodulin interacts with VIP in SSM to elicit conformational transition of VIP molecule from a predominantly random coil in aqueous environment to α helix in SSM. This process is associated with potentiation and prolongation of VIP-induced vasodilation in the in situ peripheral microcirculation.     

Surface-associated vesicles in retinal arterioles and venules

Summary The surface-associated vesicles in retinal arterioles and venules were studied after fixation in glutaraldehyde-tannic acid or after intravitreal injection of peroxidase or lactoperoxidase. The vesicles were concentrated along the abluminal (basal) surface of the endothelial cells and along the plasma membranes of smooth muscle cells in arterioles and of pericytes in post-capillary venules. They were rarely encountered in the deeper regions of these cells. In perpendicular sections through the cell surface the majority of vesicles were in continuity with the plasma membrane whereas in tangential sections, they appeared to lie free in the cytoplasm. All such vesicles were labeled after exposure to tannic acid or to the heme-proteins. Peroxidase-reaction product was never seen in the lumen of the vessels. These observations suggest that the surface vesicles in endothelial cells, smooth muscle cells and pericytes are invaginations of the plasma membrane and are thus not involved in the transcytosis or endocytosis of proteins. The vesicles in the latter two cell types may be involved in some aspect of contractility rather than pinocytosis.Supported by grants EYO4831, Research to Prevent Blindness, Inc., and the Michigan Eye Bank     

Three-dimensional organization of smooth muscle cells in blood vessels of laboratory rodents

Summary Three-dimensional aspects of smooth muscle cells of the microvas-culature were studied ultrastructurally in laboratory rodents by means of serial thin sections and reconstruction of muscle cell models. It was demonstrated that a muscle cell of an arteriole (luminal diameter (LD) 17 m) in hamster striated muscle was spindle-shaped, 70 m long, and wound twice round the vessel axis. The volume of the cell was calculated as 750 m³ and its surface area as 1330 m². A muscle cell in an arteriole (LD 6 m) in the rat retina was irregular in shape, about 22 m long, and had branched processes. The cell volume was calculated as 139 m³ and its surface area as 298 m².     

Structural alterations in proliferating,remodeling, and regressing tooth pulp arterioles

Summary In the continuously growing upper incisor of 100 g rats about 25 arterioles arise from an artery outside the tooth and pass through the apical foramen to run parallel to one another in the central part of the pulp, each supplying a well-defined sector of the migrating odontoblast layer. The arterioles pass through a cycle of proliferation, growth, remodeling, regression and decay, phase displaced in relation to each other. Proliferative and degenerative processes occur in the arteriole wall throughout the cycle, but vary considerably in intensity at different phases. Proliferation takes place by mitosis in the endothelium and the innermost smooth muscle cells. The degenerative process consists of reduction in size of smooth muscle cells by partial autodigestion and by cell death. When the odontoblasts reach the incisal extremity of the tooth, they die, and the associated regressed arteriole disappears. The system of pulpal arterioles has remarkable spatio-temporal features and each of its vessels appears to be in a state of sensitive structural equilibrium.Dedicated to the University of Copenhagen on the occasion of its 500th anniversary