Background-Dystrophin has a key role in striated muscle mechanotransduction of physical forces. Although cytoskeletal elements play a major role in the mechanotransduction of pressure and flow in vascular cells, the role of dystrophin in vascular function has not yet been investigated. Thus, we studied endothelial and muscular responses of arteries isolated from mice lacking dystrophin (mdx mice). Methods and Results-Carotid and mesenteric resistance arteries 120 m in diameter were isolated and mounted in vitro in an arteriograph to control intraluminal pressure and flow. Blood pressure was not affected by the absence of dystrophin. Pressure-induced (myogenic), phenylephrine-induced, and KCl-induced forms of tone were unchanged. Flow (shear stress)-induced dilation in arteries isolated from mdx mice was decreased by 50% to 60%, whereas dilation to acetylcholine or sodium nitroprusside was unaffected. NG-nitro-L-arginine methyl ester-sensitive flow dilation was also decreased in arteries from mdx mice. Thus, the absence of dystrophin was associated with a defect in signal transduction of shear stress. Dystrophin was present in vascular endothelial and smooth muscle cells, as shown by immunolocalization, and localized at the level of the plasma membrane, as seen by confocal microscopy of perfused isolated arteries. Conclusions-This

Abstract-We have previously shown that angiotensin II (Ang II) and pressure increase extracellular signal-regulated kinase (ERK) 1/2 activity synergistically in intact, pressurized resistance arteries in vitro. However, the mechanisms by which pressure and Ang II activate ERK1/2 in intact resistance arteries remain to be determined. The purpose of the present study was to investigate the involvement of Rho-kinase and the actin filament network in Ang II-and pressure-induced ERK1/2 activation, as well as in the contractile response induced by Ang II. Mesenteric resistance arteries (200 to 300 m) were isolated, mounted in an arteriograph, and stimulated by pressure, Ang II, or both. Activation of ERK1/2 was then measured by an in-gel assay. In mesenteric resistance arteries maintained at 70 mm Hg, Ang II (0.1 mol/L) induced contraction (29Ϯ1.4% of phenylephrine, 10 mol/L-induced contraction) and significantly increased ERK1/2 activity. Selective inhibition of Rho-kinase by Y-27632 (10 mol/L) and selective disruption of the actin filament network by cytochalasin B (10 mol/L) both decreased the Ang II-induced contraction by 78Ϯ1.2% and 87Ϯ1.9%, respectively, and significantly diminished ERK1/2 activity. In the absence of Ang II, increasing intraluminal pressure from 0 to 70 or 120 mm Hg increased ERK1/2 activity. ERK1/2 activity at 120 mm Hg was similar to that observed at 70 mm Hg in the presence of Ang II. Pressure-induced ERK1/2 activation was markedly attenuated by cytochalasin B but not by Y-27632. These results indicate that whereas pressure-induced ERK1/2 activation requires an intact actin filament network, but not Rho-kinase, the activation of ERK1/2 and the contraction induced by Ang II require both Rho-kinase and an intact actin filament network in isolated, intact mesenteric resistance arteries. Key Words: Ang II Ⅲ MAP-kinase Ⅲ Rho-kinase Ⅲ actin filament network Ⅲ resistance arteries H igh luminal pressure and angiotensin II (Ang II) are both involved in the pathogenesis of cardiovascular diseases, such as hypertension. Hypertension is characterized by increased vascular resistance associated with changes in arterial wall structure and function in resistance arteries. 1,2 Ang II receptors are coupled to a wide variety of signal transduction elements, including protein kinase C, c-Src tyrosine kinase, protein tyrosine phosphorylation, and extracellular signalrelated kinase (ERK) 1/2. 3-6 These pathways certainly play an important role in the regulation of vascular tone. 7 We and others have previously shown that mechanical strain in the vessel wall induced by pressure activates ERK1/2 in vascular smooth muscle cells (VSMCs) both in vivo and in vitro. 3,8 -10 However, scare information is available on the cellular signaling pathways mediating Ang II-induced contraction and on its possible interaction with pressure in the activation of ERK1/2, especially in intact resistance arteries.Recent findings suggest that the small GTPase Rho and its target Rho-kinase play a crucial role in the regulation of blood...

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Erectile dysfunction (ED) is another manifestation of vascular disease. We evaluated the natural history of ED in the spontaneously hypertensive rat (SHR) and the respective participation of associated pathophysiological modifications, i.e., endothelial dysfunction and tissue remodeling. SHR and their normotensive counterparts [Wistar-Kyoto rats (WKY)] of 6, 12, and 24 wk of age (n = 12) were used to evaluate erectile function, erectile and aortic tissue reactivity, and remodeling. Erectile responses in SHR are reduced at all ages (P < 0.001). In both aortic and erectile tissues of SHR and WKY, relaxations to ACh are altered progressively with age, although more markedly in SHR. They are decreased at 12 wk of age in erectile tissue of SHR compared with WKY (maximal relaxation: -19.2 +/- 2.8% vs. -28.3 +/- 3.9%, P < 0.001) but only at 24 wk of age in aortas (-47.9 +/- 6.4% vs. -90.5 +/- 2.9%, P < 0.001). Relaxations to sodium nitroprusside are unaltered in aortic rings of both strains but enhanced in erectile tissue of SHR at 12 wk of age. Major modifications in the distribution of collagen I, III, and V in SHR occur in both types of tissue and are detectable sooner in erectile tissue compared with aortic tissue. The onset of ED is detectable before the onset of hypertension in the SHR. Structural and functional alterations, while similar, occur earlier in erectile compared with vascular tissue. If confirmed in humans, ED could be an early warning sign for hypertension, and common therapeutic strategies targeting both ED and hypertension could be investigated.

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Background and purpose: The mechanism(s) of action responsible for the beneficial effects of phosphodiesterase 5 (PDE5) inhibitors including sildenafil on lower urinary tract symptoms suggestive of benign prostate hyperplasia are unclear. In particular, the role of the NO-cGMP signalling pathway in regulating human bladder dome smooth muscle relaxation is questionable. Thus, we assessed the ability of a PDE5 inhibitor, sildenafil, to relax such tissue, and identified the signalling pathways involved in this relaxation. Experimental approach: Human bladder samples were obtained from 20 patients with no overactive bladder undergoing cystectomy for bladder cancer. Detrusor strips were mounted isometrically in Krebs-HEPES solution. Concentration-response curves for sildenafil (10 nM-30 mM) were generated in the presence of various inhibitors on carbachol-induced pre-contraction. Key results: Sildenafil relaxed carbachol-pre-contracted human detrusor strips, starting at 3 mM. This effect was not modified by NO donors, S-nitroso-N-acetylpenicillamine (10 mM) or sodium nitroprusside (300 nM), but was significantly inhibited by inhibition of guanylate cyclase (with ODQ, 10 mM) or adenylyl cyclase (with MDL-12,330A, 10 mM), by the ATP-sensitive potassium channel inhibitor, glibenclamide (10 mM), or inhibition of the large (with iberiotoxin, 30 nM) or small (with apamin, 100 nM) conductance calcium-activated potassium channels. Conclusions and implications:Sildenafil-induced relaxation of human detrusor smooth muscle involved cGMP-, cAMP-and K + channel-dependent signalling pathways, with a minor contribution from NO. The effect of this sildenafil-induced relaxation on the clinical benefit of PDE5 inhibitors on urinary storage symptoms in men deserves further investigation.

suburothelium were mounted isometrically in organ baths filled with Krebs-HEPES (37 ° C; 95% O 2 /5% CO 2 ). Strips were incubated with 10 μ M pinacidil (K ATP opener) followed by 10 μ M glibenclamide (K ATP blocker). In another set of experiments, strips were incubated with 30 μ M NS-1619 (BK Ca opener) followed by 100 n M iberiotoxin (BK Ca blocker) or with 100 n M apamin (SK Ca blocker). RESULTSSCA occurred more frequently with larger amplitude and area under the curve in detrusor strips from NDO patients compared to control patients. The presence of urothelium/suburothelium did not significantly modify SCA in either patient population. Pinacidil markedly inhibited SCA of detrusor strips from control and NDO patients. This effect was reversed by glibenclamide. By contrast, NS-1619 followed by iberiotoxin did not elicit any significant changes in SCA from NDO patients, contrary to control patients. CONCLUSIONSK ATP and SK Ca channels regulate SCA of NDO patients' detrusor strips. By contrast, BK Ca channels are not involved in the regulation of detrusor SCA in NDO patients, whereas they regulate SCA in control patients. These results should be considered in the development of K + channels openers for the treatment of NDO. Moreover, SCA observed in vitro should be regarded as an in vitro modelling of human NDO.

Low intensity extracorporeal shock wave therapy improved erectile function in GK rats. Unexpectedly, this was not mediated by a nitric oxide/cyclic guanosine monophosphate dependent mechanism. Sildenafil increased shock wave efficacy. This preclinical paradigm to deliver low intensity extracorporeal shock wave therapy to the rat penis should help further exploration of the mode of action of this therapy on erectile tissue.