Characteristics of myogenic reactivity in isolated rat mesenteric veins

Abstract

Enouri S, Monteith G, Johnson R. Characteristics of myogenic reactivity in isolated rat mesenteric veins. Am J Physiol Regul Integr Comp Physiol 300: R470 -R478, 2011. First published December 1, 2010; doi:10.1152/ajpregu.00491.2010.-Mechanisms of mechanically induced venous tone and its interaction with the endothelium and key vasoactive neurohormones are not well established. We investigated the contribution of the endothelium, L-type voltage-operated calcium channels (L-VOCCs), and PKC and Rho kinase to myogenic reactivity in mesenteric vessels exposed to increasing transmural pressure. The interaction of myogenic reactivity with norepinephrine (NE) and endothelin-1 (ET-1) was also investigated. Pressure myography was used to study isolated, cannulated, third-order rat mesenteric small veins and arteries. NE and ET-1 concentration response curves were constructed at low, intermediate, and high transmural pressures. Myogenic reactivity was not altered by nitric oxide synthase inhibition with N -nitro-L-arginine (L-NNA; 100 M) or endothelium removal in both vessels. L-VOCCs blockade (nifedipine, 1 M) completely abolished arterial tone, while only partially reducing venous tone. PKC (chelerythrine, 2.5 M) and Rho kinase (Y27632, 3 M) inhibitors largely abolished venous and arterial myogenic reactivity. There was no significant difference in the sensitivity of NE or ET-1-induced contractions within vessels. However, veins were more sensitive to NE and ET-1 when compared with corresponding arteries at low, intermediate, and high transmural pressures, respectively. These results suggest that 1) myogenic factors are important contributors to net venous tone in mesenteric veins; 2) PKC and Rho activation are important in myogenic reactivity in both vessels, while L-VOCCs play a limited role in the veins vs. the arteries, and the endothelium does not appear to modulate myogenic reactivity in either vessel type; and 3) mesenteric veins maintain an enhanced sensitivity to NE and ET-1 compared with the arteries when studied under conditions of changing transmural distending pressure. myogenic tone; myogenic responses; mesenteric small arteries; signal transduction; vasoactive agents THE PREVAILING LEVEL OF VASOMOTOR tone within a segment of the circulation is controlled primarily by sympathetic neurogenic influences, intrinsic myogenic properties of the vascular smooth muscle (VSM), and key local or circulating humoral factors (16,32,38). Varying contributions from these factors, in part, provide functional specialization of the veins vs. the arteries in a particular vascular bed while enabling the cardiovascular system to meet the changing demands of the body. Several studies conducted in veins including facial, saphenous, portal, skeletal muscle, and bat wing (3,6,7,15,18) have described myogenic tone in these vessels. However, the strength of myogenic tone varies between veins, being dependent on the function of the vascular bed and its contribution to venous capacitance. Pressure-induced myogenic tone in rat saphenou...

Hydrogen peroxide via thromboxane A2 receptors mediates myogenic response of small skeletal muscle veins in rats

“…The remaining, catalase-insensitive portion of myogenic response of small veins is likely to be mediated directly by L-type voltage-operated calcium channels, PKC and Rho kinase pathways [24]. Also, in our previous studies on small isolated arteries we have also shown that increased intraluminal pressure elicits the release of reactive oxygen species [18,74], which may also oparetes in venous vessles as well [62,63].…”

“…Among others, recent studies suggest a role of prostaglandins [62] and L-type voltage-operated calcium channels, PKC and Rho kinase [24] in regulating the diameter of small veins in response to intraluminal pressure [62,63], but the exact signaling still needs to be further investigated. Because a previous study in mouse tail arterial vessels showed that pressure induced myogenic tone is mediated by H 2 O 2 [59] and in venous circulation it is quite often that there is increased production of reactive species [12,51,62], we set up the hypothesis that H 2 O 2 contribute to the mediation of myogenic response in small skeletal muscle veins.…”

“…Recent studies suggest that myogenic response is present in small veins and venules of different organs [8,22,44] and species and even in humans [8,31]. Regarding the mediation of myogenic response, recent studies suggest a role of prostaglandins [62] and L-type voltage-operated calcium channels, PKC and Rho kinase [24] in regulating the diameter of small veins in response to intraluminal pressure, but the exact signaling, which activates these pathways are not known. In arterial vessels, higher intravascular pressures elicit release of reactive oxygen species, such as H 2 O 2 and also previous studies in mouse tail arterial vessels showed that pressure-induced myogenic tone is mediated by H 2 O 2 [59].…”

Maxi-K channel (BKC a ) activity veils the myogenic tone of mesenteric artery in rats

“…; Enouri et al. ). Nevertheless, a closer inspection of literature reveals that the MT of MA (MT MA ) is less consistent in the absence of agonists (VanBavel et al.…”

Vázizomkisvénák vazomotortónusának intrinszik szabályozómechanizmusai

“…A mechanizmus jelenlétét denevér szárny-, több faj portalis, tengerimalac mesenterialis, kutya, humán és patkány saphena-, valamint sertéscoronaria kisvénáiban igazolták [27][28][29][30][31][32]. In vivo és in vitro kísérletekben kimutatták, hogy patkány vena saphenáiban akut nyomáster-helés hatására jelentősen megnőtt a vénák miogén vá-laszképessége, tónusa.…”