Independent Regulation of Periarteriolar and Perivenular Nitric Oxide Mechanisms in the In Vivo Hamster Cheek Pouch Microvasculature

Objective: We tested the hypothesis that differential stimulation of nitric oxide (NO) production can be induced in pre‐ and postcapillary segments of the microcirculation in the hamster cheek pouch. Materials and Methods: We applied acetylcholine (ACh) or platelet‐activating factor (PAF) topically and measured perivascular NO concentration ([NO]) with NO‐sensitive microelectrodes in arterioles and venules of the hamster cheek pouch. We also measured NO in cultured coronary endothelial cells (CVEC) after ACh or PAF. Results: ACh increased periarteriolar [NO] significantly in a dose‐dependent manner. ACh at 1 μM increased [NO] from 438.1±43.4 nM at baseline to 647.9±66.3 nM, while 10 μM of ACh increased [NO] from baseline to 1,035.0±59.2 nM (P<0.05). Neither 1 nor 10 μM of ACh changed perivenular [NO] in the hamster cheek pouch. PAF, at 100 nM, increased perivenular [NO] from 326.6±50.8 to 622.8±41.5 nM. Importantly, 100 nM of PAF did not increase periarteriolar [NO]. PAF increased [NO] from 3.6±2.1 to 455.5±19.9 in CVEC, while ACh had no effect. Conclusions: We conclude that NO production can be stimulated in a differential manner in pre‐ and postcapillary segments in the hamster cheek pouch. ACh selectively stimulates the production of NO only in arterioles, while PAF stimulates the production of NO only in venules.     

IL-1β增强主动脉平滑肌细胞内Ⅰ型IP3受体表达

目的：探讨白细胞介素1(IL-1)对主动脉平滑肌细胞株(A7r5细胞)Ⅰ型珉受体蛋白过度表达的影响。方法：通过对主动脉平滑肌细胞培养，应用蛋白杂交技术、核酸杂交技术分别检测在IL-1β作用后，主动脉平滑肌细胞中Ⅰ型三磷酸肌醇(IP3)受体蛋白和Ⅰ型IP3受体mRNA的表达及Ⅰ型IP3受体mRNA半衰期的测定，同时研究IL-1β对Ⅰ型IP3受体基因启动子的作用。结果：IL-1β能增强主动脉平滑肌细胞内的Ⅰ型IP3受体蛋白的表达，两者呈剂量依赖关系；IL-1β也能使Ⅰ型IP3受体mRNA水平增高；通过对Ⅰ型IP3受体mRNA半衰期的测定明确IL-1β对Ⅰ型IP3受体mRNA影响不是抑制mRNA的降解，而是诱导其表达增加。IL-1β作用4小时时，装有Ⅰ型玛受体启动子的质粒上的报告基因表达增加，而8小时时，报告基因的表达即降至IL-1β作用前的水平。结论：IL-1可能作用于Ⅰ型IP3受体mRNA的基因启动子，使Ⅰ型IP3受体mRNA合成增加，导致Ⅰ型IP3受体蛋白表达增加，由此构成了主动脉平滑肌细胞内储备Ca^2 释放，引起动脉平滑肌细胞收缩、舒张功能异常的病理生理基础。     

In vivo effects of endothelin-2, endothelin-3 and ETA receptor blockade on arterial,venous and capillary functions in cat skeletal muscle

Ekelund , U. 1994. In vivo effects of endothelin-2, endothelin-3 and ET_A receptor blockade on arterial, venous and capillary functions in cat skeletal muscle. Acta Physiol Scand 150, 47–56. Received 31 March 1993, accepted 25 May 1993. ISSN 0001–6772. Department of Physiology & Biophysics, University of Lund, Sweden. This study describes, in quantitative terms, the effects of endothelin-2 and endothelin-3 on vascular tone (resistance) in large-bore arterial resistance vessels (> 25 /μm), small arterioles (< 25 μm) and the veins, as well as on capillary pressure and fluid exchange in cat gastrocnemius muscle in vivo. Infusion of endothelin-2 or endothelin-3 (200–1600 ng kg^-1 min^-1, i.a.) elicited an initial transient dilation, followed by a dose-dependent, slowly developing constrictor response, being maintained after cessation of the infusion. At the dose of 400 ng kg^-1 min^-1 (n= 9), infused i.a. during 20 min, endothelin-2 caused an average increase in total regional vascular resistance of 80%, and endothelin-3 of 35%, and the site of constrictor action of both peptides was preferentially located to the small arterioles. Endothelin-2 also constricted the veins and, hence, evoked a pronounced capacitance response, whereas endothelin-3 was devoid of any venoconstrictor effect. This difference, via effects on the pre-/post-capillary resistance ratio, led to a more pronounced fall of capillary pressure in response to endothelin-3 than to endothelin-2. The new specific competitive ET_A receptor antagonist, FR 139317, abolished the vasoconstrictor response to both endothelin-2 and endothelin-3 in vivo, whereas the preceding vasodilator responses were unaffected. These results, taken together with those of our previous analogous study of the effects of endothelin-1, indicated that all three endothelins were approximately equally as effective in eliciting the transient dilator response in skeletal muscle in vivo, whereas the order of vasoconstrictor activity was endothelin-1 > endothelin-2 > endothelin-3. Due to an especially pronounced venoconstrictor activity of endothelin-1, this peptide, in contrast to endothelin-2 and -3, evoked a rise in capillary pressure, with a consequent net transcapillary fluid filtration and muscle tissue oedema formation. The results further indicated that the vasoconstrictor responses to all endothelins in skeletal muscle were mediated by the ET_A receptor, whereas the initial transient vasodilator responses seemed to be mediated by the ET_B receptor.     

盐酸埃他卡林扩血管特征的研究

目的 观察新型抗高血压药盐酸埃他卡林对大、小动脉扩张作用的药理学特征。方法 采用大鼠主动脉离体血管环和尾动脉螺旋状血管条两种组织来对比分析盐酸埃他卡林的扩血管作用。结果 盐酸埃他卡林在10^-7～10^-3mol／L范围内对氯化钾预致收缩的大鼠尾动脉血管条产生剂量依赖性舒张反应,且具有部分内皮依赖性,但对主动脉离体血管环无明显的舒张反应,该作用在高血压状态时显著增强,能被ATP敏感性钾通道特异性阻断剂格列苯脲阻断。结论 盐酸埃他卡林具有选择性舒张小动脉的作用,该作用与其激活ATP敏感性钾通道有关。     

The Effect of Ovariectomy and Estrogen on Penetrating Brain Arterioles and Blood‐Brain Barrier Permeability

Objective : We investigated the effect of estrogen replacement on the structure and function of penetrating brain arterioles (PA) and blood‐brain barrier (BBB) permeability. Materials and Methods : Female ovariectomized Sprague‐Dawley rats were replaced with estradiol (E₂) and estriol (E₃) (OVX + E;N=13) and compared to ovariectomized animals without replacement (OVX; N=14) and intact controls (CTL, proestrous; N=13). Passive and active diameters, percent tone, and passive distensibility of pressurized PA were compared. In addition, BBB permeability to Lucifer Yellow, a marker of transcellular transport, was compared in cerebral arteries. Results : Ovariectomy increased myogenic tone in PA, compared to CTL, that was not ameliorated by estrogen treatment. Percent tone at 75 mmHg for CTL vs. OVX and OVX + E was 44±3% vs. 51±1% and 54±3% (P<0.01 vs. CTL for both). No differences were found in passive diameters or distensibility between the groups. BBB permeability increased 500% in OVX vs. CTL animals; however, estrogen replacement restored barrier properties: flux of Lucifer Yellow for CTL, OVX, and OVX + E was (ng/mL): 3.4±1.2, 20.2±5.3 (P<0.01 vs. CTL), and 6.15±1.2 (n.s.). Conclusions : These results suggest that estrogen replacement may not be beneficial for small‐vessel disease in the brain, but may limit BBB disruption and edema under conditions that cause it.     

Microvascular endothelium isolation with microcarriers: Arterial,venous

Summary In this paper we describe a method whereby the lungs of a small laboratory animal or a lobe of lung of large animal are perfused blood-free. A cold solution (4°C) containing EDTA and microcarriers (40 to 80 µm diameter) is pumped into the lungs. The loosened endothelial cells are collected by the tight fit of the microcarriers in vessels of the microcirculation. Cells can be obtained from precapillary or postcapillary vessels. The resultant harvest of endothelial cells on beads is plated into flasks. The endothelial cells migrate from the microcarriers and establish monolayers on the flasks.     

Responses of single arterioles in vivo in cat skeletal muscle to change in arterial pressure applied at different rates

The concept of a rate-dependent, dynamic as well as a static component in the myogenic control has been suggested in some previous in vitro and whole organ investigations. The present study is an attempt to reveal a dynamic component in the myogenic response directly on single arterioles by a vital microscopic technique. The study was made on the autonomically blocked vascular bed of cat tenuissimus muscle and performed by analysing the arteriolar diameter changes to an arterial pressure increase and decrease when applied at two different rates. The results demonstrate a transient, dynamic constrictor response upon the phasic increase in pressure and a transient, dynamic dilator response upon the phasic decrease in pressure, the magnitudes of which being related to the rate of the pressure change. The static response developing during the steady-state phase of constant increased pressure was also shown. The dynamic responses were confined to arterioles smaller than about 20 μm while the steady-state response was present in larger arterioles as well. Even if the metabolic control system partly could be responsible for the obtained responses, arguments are given that the described reactions are mainly myogenic in nature.     

An electron microscope study of arteriolar branching sites in the normal gastric submucosa of rats and in experimental gastric ulcer

Summary To observe the branching site of the rat gastric submucosal arteriole toward the mucosal capillary network, we used vascular corrosion casting, scanning electron microscopy (SEM) and transmission electron microscopy (TEM), under various conditions, including the normal state, water immersion restraint stress for 24 h, ethanol-induced ulcer and administration of low and high doses of noradrenaline. In normal rats, the branching site of the submucosal arteriole toward the mucosa was slightly narrowed, as seen in the cast observations. The SEM and TEM observations revealed that this narrowing was due to the presence of the so-called intra-arterial cushion. In the restraint stress rats, this narrowing was increased. TEM and direct SEM observation of the intra-arterial cushion showed much the same findings. In the noradrenaline administered rats, similar changes were observed but not so in the rats with an ethanol-induced ulcer. Arterio-venous-anastomoses (AVA) were not observed in the submucosa, under any of the conditions used. We suggest that the submucosal intra-arterial cushions occurring at the branching sites of the submucosal arterioles may play an important role in regulating blood flow to the gastric mucosa.     

Episodic release of renin from single isolated superfused rat afferent arterioles

Doubts have been raised about the involvement of an exocytotic event in the renin release process. This motivated the development of a technique which permitted the study of renin release from one single superfused rat afferent arteriole with a time resolution of 20 seconds.By using this technique it is shown in 43 experiments that the undisturbed renin release is episodic with a renin discharge of 45.2±3.3 (SEM) nano Goldblatt units per episode (n=114) and a frequency of one episode per 5 min. The total renin content of one arteriole was about 30 GU. The renin discharge and frequency correspond to calculated values for the renin content of single juxtaglomerular cell granules and the release rates in vivo, respectively. Release activity could be stimulated by an acute decrease in the osmolality of the superfusion medium (–20 mOsm sucrose,n=14) indicating that an osmotic water movement is involved in the secretory process.This study provides functional evidence that renin release is exocytotic. In addition it reports what appears to be the first direct measurement of release of secretory material compatible with secretion of single granules from any secretory system.The present results were presented in preliminary form at Vth European Colloquium on Renal Physiology, Frankfurt am Main 1985, Abstract no. 32     

Cytoplasmic sequestration phenomena in smooth muscle cells of kidney resistance vessels and epithelioid cells of the juxtaglomerular apparatus

Summary The occurrence of vacuoles in cells of contractile tissues and especially in media cells of resistance vessels has been known for quite some time. Recently, it has been widely accepted that these vacuoles, characteristically lined by a double membrane, result from herniation of one vascular smooth muscle cell into the other as a result of vasoconstriction. In our electronmicroscopic investigations we found double membrane-bounded vacuoles not only in kidney resistance vessels of rats and mice under conditions of vasoconstriction, but also in control animals and animals with maximal renal vasodilation. Part of our observations are compatible with the assumption that such vacuoles arise from a damage of club-shaped, musculo-muscular contacts due to shape changes of media cells during maximal vasoconstriction or vasodilation. However, serial thin sectioning revealed that some of the cytoplasmic vacuoles have no connections with neighbouring cells. This finding and various parallels to the generation of autophagic vacuoles indicate that the so-called herniations may also represent demarcations of large cytoplasmic areas within an individual cell. Irrespective of the origin of these vacuoles, their contents show different stages of deterioration. At later stages, the vacuoles appear to be adjacent, with only one membrane, to the extracellular space, into which they are believed to discharge finally. Cytoplasmic vacuolization has not only been observed in smooth muscle cells, but also in juxtaglomerular epithelioid cells of the afferent arteriole. Here the vacuoles - besides other organelles - also contain secretory granules; it is therefore proposed that autophagic phenomena with final extrusion of cytoplasmic material may be involved in the programmed down-regulation of the granular renin store following inhibition of renin synthesis and secretion.These studies were supported by the German Research Foundation within the Forschergruppe Niere, Heidelberg