Contractile Effect Of Phenylephrine Research Articles

Angiotensin II‐Induced Contraction is Mediated by Activation of Polo‐Like Kinase 1 (Plk1) in Pudendal and Mesenteric Resistance Arteries of Mice

BackgroundPolo‐like kinase 1 (Plk1) is a Ser/Thr protein kinase that plays a role in cell cycle regulation. Recently, Plk1 was demonstrated to be required for arterial structure organization and its absence caused aortic rupture and death, being also required for RhoA activation and vasoconstriction in aorta. In this study, we aimed to investigate the role of Plk1 in the contraction of resistance arteries in response to different classes of contractile agents. We hypothesize that agonist‐mediated contraction is dependent on activation of Plk1 in resistance arteries in both males and females.MethodsMale and female wild type mice were used in this study. The pudendal and mesenteric resistance arteries were isolated and mounted in a wire‐myograph. Contractions were obtained by concentration‐response curves to phenylephrine (PE), serotonin (5‐HT), thromboxane A2 analogue U46619 and angiotensin II (Ang‐II). Concentration response curve to the same agonist was repeated after incubation with Plk1 inhibitor Volasertib (100 nM or 1 uM). Contractions in the presence of Volasertib were calculated as percentage of the maximal contraction evoked by its respective agonist in control conditions, which was considered 100%. Expression of Plk1 was evaluated by western blot using mesenteric artery in control conditions and after incubation with Ang‐II, with or without the Plk1 inhibitor volasertib. Curves to Ang‐II were also repeated in the absence of any inhibitor in order to rule out tachyphylaxis of Ang‐II in the second curve. Paired Student’s t‐test was used for data analysis. Data are expressed as mean ± S.E.M of 3‐5 mice.ResultsIn male, the contractile effects of PE, 5‐HT, U46619 and Ang‐II in the pudendal and mesenteric arteries were evaluated in the presence of the Plk1 inhibitor, Volasertib (100 nM). Plk1 inhibition did not affect the contraction induced by PE, 5‐HT and U46619 in either pudendal or mesenteric arteries. On the other hand, the contraction induced by Ang‐II was markedly reduced in the presence of Volasertib (100 nM) in both pudendal and mesenteric arteries (Fig 1A and 1C, respectively). However, the inhibition of the contraction was not dependent on the dose, since 1 uM of Volasertib did not cause further inhibition (Pudendal artery EMAX: 3.86 ± 0.97% vs 5.02 ± 0.48%, in the presence of 100 nM and 1 uM of Volasertib, respectively; Mesenteric artery EMAX: 0.28 ± 0.21% vs 0.36 ± 0.18%, in the presence of 100 nM and 1 uM of Volasertib, respectively). In females, only 100 nM of Volasertib was tested in the contraction induced by PE and Ang‐II. In females, Volasertib did not affect the contraction induced by PE in pudendal and mesenteric arteries. In contrast, the contraction induced by Ang‐II was markedly reduced in the presence of Volasertib 100 nM (Fig 1B and 1D). Plk1 is expressed in the mesenteric artery of wild type mice, however, it was not affected by incubation with either Ang‐II (100nM) or Volasertib (100 nM). However, it is possible that these treatments are affecting Plk1 phosphorylation.ConclusionOur findings are the first to demonstrate that Plk1 plays a role in Ang‐II‐induced contraction of the pudendal and mesenteric arteries of mice. More studies are necessary to elucidate the process of Plk1 activation and its association with vascular dysfunction in pathological conditions such as hypertension and diabetes.

Participation of COX-1 and COX-2 in the contractile effect of phenylephrine in prepubescent and old rats.

Vascular reactivity can be influenced by the vascular region, animal age, and pathologies present. Prostaglandins (produced by COX-1 and COX-2) play an important role in the contractile response to phenylephrine in the abdominal aorta of young rats. Although these COXs are found in many tissues, their distribution and role in vascular reactivity are not clear. At a vascular level, they take part in the homeostasis functions involved in many physiological and pathologic processes (e.g., arterial pressure and inflammatory processes). The aim of this study was to analyze changes in the contractile response to phenylephrine of thoracic/abdominal aorta and the coronary artery during aging in rats. Three groups of rats were formed and sacrificed at three distinct ages: prepubescent, young and old adult. The results suggest that there is a higher participation of prostanoids in the contractile effect of phenylephrine in pre-pubescent rats, and a lower participation of the same in old rats. Contrarily, there seems to be a higher participation of prostanoids in the contractile response of the coronary artery of older than pre-pubescent rats. Considering that the changes in the expression of COX-2 were similar for the three age groups and the two tissues tested, and that expression of COX-1 is apparently greater in older rats, COX-1 and COX-2 may lose functionality in relation to their corresponding receptors during aging in rats.

The analysis of transduction mechanisms associated with an acute action of homocysteine on isolated rat femoral artery.

The present study was undertaken in order to examine transduction mechanism involved in the single application of 100 μM homocysteine (Hcy) on isolated rat femoral artery (RFA) rings equilibrated on the basal tone; to establish if a single application of 100 μM Hcy alters contractile effect of phenylephrine (Phe), or oppositely the relaxant effect of acetylcholine (ACh) or bradykinin (BK) after 60-min-long incubation of 100 μM Hcy; and finally to identify morphological changes on the vascular wall after a 24-h-long incubation of 100 μM Hcy. Hcy produced contractile response of intact RFA, which was increased after endothelial denudation, while decreased by urapidil (an α1 receptor blocker), nifedipine (a voltage-gated L-type Ca++ channel blocker) or indomethacin (a cyclooxygenase inhibitor). The initial RFA contraction evoked by Phe was further increased by the single addition of Hcy, which was not the case when ouabain (an inhibitor of Na+/K+-ATPase) was preincubated. After 60-min-long incubation of Hcy relaxant actions of ACh and BK were unaltered, equieffective and equipotent. A 24-h-long incubation of RFA rings with Hcy produced an impairment of vascular endothelium, expressed as a minor or more pronounced interruption of endothelial cells.

Changes during development of COX 1 and 2 in heart, abdominal and thoracic aorta (837.11)

Cyclooxigenase 1 and 2 have been related in the release of prostanoids that regulate the effect of various agonists as in the case of phenylephrine, but its unknown that how this enzyme is involved in the contractile response to phenylephrine age‐dependent. The aim of this paper is to analyze changes of COX 1 and 2 involvements in the contractile response to phenylephrine in the thoracic and abdominal aorta and coronary artery of pubescent, young and old rats. It has been describe that during development there are changes in the activity of some enzymatic pathways, in this work we analyze the change in the involvement of cyclooxygenase and PGs in the contractile effect of phenylephrine with age. Methods: we used male rats of 6, 16 weeks and 1 year of age. Rats were anesthetized with pentobarbital (50 mg / kg), after that we proceeded to obtain the thoracic aorta and abdominal aorta and the heart and they were placed in an isolated organ system where we proceeded to make concentration response curves to phenylephrine. On the other hand we obtain heart and aorta for the western blot analysis and the immunohistochemistry assay of COX 1 and COX 2. Conclusions: COX1 increase during development. On the other hand COX2 decrease in the elderly stage only in thoracic aorta.Grant Funding Source: COFAA / IPN

Participation of cyclooxygenase and PGs E2 and F2alfa during the development of the rat in the contractile effect of phenylephrine in rat aorta and coronary artery

The aim of this paper is to analyze the changes of cyclooxygenase (COX) and prostaglandins (PGs) E2 and F2alfa involvement in the contractile response to phenylephrine in the thoracic and abdominal aorta and coronary artery of prepubertal young and old rats. It has been describe that during development there are changes in the activity of some enzymatic pathways, in this work we analyze the change in the involvement of cyclooxygenase and PGs in the contractile effect of phenylephrine with age. COX 1 and 2 have been related in the release of prostanoids that regulate the effect of various agonists as in the case of phenylephrine, but its unknown that how this enzyme is involved during the development of the rat cardiovascular level. In this experimental model we used male rats of 6, 16 weeks and 1 year of age. Rats were anesthetized with pentobarbital (50 mg/kg), after that we proceeded to obtain the thoracic aorta and abdominal aorta and the heart. The aortic rings were placed in an isolated organ system which keeps the tissue in physiological Krebs solution at a temperature of 37 ° C and bubbled with carbogen (95% O2 and 5% CO2) and the other hand the heart were placed in a Langendorf system. Then we proceeded to make concentration response curves to phenylephrine (10–9 to 10–5M) in the presence and absence of indomethacin, NS 398 and Sc560 (COX antagonist). We obtain 20mg of either heart, thoracic or abdominal aorta for the western blot analysis of COX 1 and COX 2 and for the PGS measurement. Results showed differences in participation of this enzyme and PGs in the contractile response to phenylephrine age‐dependent rat.

The influence of constitutive cox-2 in smooth muscle tissue on the contractile effect of phenylephrine in the rat abdominal aorta

Prostanoids are involved in the phenylephrine-induced contraction of the aorta. Here, we examined whether or not constitutive cyclooxygenase-2 (phosholipases C and A2) is the source of prostanoids in the smooth muscle of the arterial wall of the thoracic and abdominal aorta. Both cyclooxygenase isoforms (COX-1 and COX-2) were expressed in the two aortic segments, but their expression was not altered by phenylephrine, the protein synthesis inhibitor cycloheximide, or the phospholipase A2 inhibitors arachidonyl trifluoromethyl ketone and methyl arachidonyl fluorophosponate. Indomethacin and NS398, which are a non-selective and selective COX-2 inhibitor, respectively, but not SC-560, which is a COX-1-selective inhibitor, inhibited the effect of phenylephrine on the abdominal, but not the thoracic, aorta. Similarly, U73122, which is a phospholipase C inhibitor, and RHC80267, which is a diacylglycerol lipase inhibitor, inhibited the effect of phenylephrine. These findings suggest that prostanoids, which are produced by constitutively active COX-2, influence the contractile response of the abdominal aorta and that the production of arachidonic acid relies on phospholipase C and diacylglycerol lipase.

Pharmacological study of the internal and sphincter in patients with chronic anal fissure.

A pharmacological study of the internal anal sphincter (IAS) was undertaken in patients with chronic and fissure. The sensitivity of the IAS to the contractile effect of phenylephrine and potassium chloride and to relaxation by isoproterenol was evaluated. Supersensitivity of the IAS to relaxation by isoproterenol was noted. Further research is necessary to determine the pharmacological basis of such a disturbance.

The thrombin inhibitor argatroban does not influence the endothelium-dependent relaxant and contractile responses of isolated rabbit carotid arteries

Atherosclerotic endothelial dysfunctions are associated with a reduced NO production, which is probably due to impaired NO synthase (eNOS) activity or a deficiency of the substrate L-arginine. In the present studies, the influence of argatroban on isolated rabbit carotid arteries was investigated to determine whether the arginine derivative argatroban can improve the endothelium-dependent relaxation. Rings from rabbit carotid arteries were placed in 10 ml organ baths for isometric tension recording. Endothelial integrity was assessed by the acetylcholine-induced relaxation of PGF2alpha-precontracted rings; after mechanical removal of the endothelium the relaxation was abolished. Preincubation of the vessels in vitro with L-NAME, an inhibitor of the eNOS, diminished significantly the acetylcholine-induced relaxation by more than 50%. After i.v. application of L-NAME (100 mg/kg) in rabbits, relaxation in response to acetylcholine was significantly reduced compared to the control when the vessels were studied ex vivo in an organ bath. The contractile effects of phenylephrine and 5-HT were slightly enhanced. Argatroban is a selective, potent, synthetic thrombin inhibitor; after i.v. application at doses of 0.5 and 1.0 mg/kg, a significant prolongation of the plasma coagulation time (measured as thrombin time and a PTT) of up to 60 min was found in rabbits. In vitro argatroban did not affect the acetylcholine-induced relaxation or the contractile response to phenylephrine and 5-HT. After i.v. application, the ex vivo experiments in the organ bath showed that after 30 min the relaxant responses of the carotid arteries to acetylcholine and the contractile effects of phenylephrine and 5-HT were not influenced by pretreatment with argatroban. The present studies suggest that argatroban has no vascular effects in vitro and ex vivo in normal rabbits.

Possible involvement of K+ channel opening to the interleukin-1 beta-induced inhibition of vascular smooth muscle contraction.

We have previously shown that interleukin-1 beta relaxes vascular smooth muscle by the NO-dependent and independent mechanisms (Takizawa et al.: Eur. J. Pharmacol. 330: 143-150, 1997). In this study, we investigated the mechanism of NO-independent relaxation. Treatment of the rat aorta with interleukin-1 beta for 24 hr inhibited the high-K+ induced contraction by decreasing cytosolic Ca2+ level ([Ca2+]i). The relationship between [Ca2+]i and tension in intact muscle and the pCa-tension curves in permeabilized muscle suggested that Ca2+ sensitivity of contractile element was not changed after the interleukin-1 beta-treatment. After a treatment with interleukin-1 beta for 24 hr, contractile effects of phenylephrine (1 microM-10 microM) were markedly inhibited in the presence of L-NMMA (100 microM) applied to inhibit NO synthesis. A blocker of ATP-sensitive K+ channel, glibenclamide (1 microM), partially recovered the interleukin-1 beta-induced inhibition. In contrast, a blocker of Ca(2+)-activated K+ channel, charybdotoxin (0.1 microM), was ineffective. These results suggest that membrane hyperpolarization due to activation of ATP-sensitive K+ channels may partly be responsible for the NO-independent mechanism of interleukin-1 beta-induced inhibition of vascular smooth muscle contraction.

Effect of Ovalbumin Challenge on Endothelial Reactivity of Pulmonary Arteries from Sensitized Guinea-pigs

Summary: It has been generally demonstrated that sensitization process and/or specific antigen challenge causes an increase in the responsiveness of airway smooth muscle preparations to contractile agonists. However, there is no report elucidating such modifications in vascular preparations. In this study, we examined the influence of ovalbumin sensitization and challenge on the reactivity of guinea-pig pulmonary arteries to various vasoactive agents. Guinea-pigs were actively sensitized to ovalbumin (10 mg/kg) by i p injections on days 1, 3 and 5. Beginning 21 days after the last injection, animals were challenged with ovalbumin either in vitro or in vivo. The effects of sensitization process and challenge were studied on endothelium-dependent and -independent responses of guinea-pig pulmonary arteries. Ovalbumin challenge but not sensitization process significantly reduced the endothelium-dependent relaxant responses to acetylcholine and histamine. Similar reductions were also observed in the responses of calcium ionophore, A 23187. However, no alteration was observed in the responses to glyceryl trinitrate and potassium chloride which excludes an abnormality in the relaxant and contractile capacities of pulmonary artery smooth muscle following sensitization and challenge. In addition, an enhancement was observed in the contractile effect of phenylephrine after ovalbumin sensitization and challenge different from U 46619, a thromboxane analogue, and potassium chloride induced contractions. Incubation of the sensitized arteries with the mast cell stabilizer, disodium cromoglycate but not with the free radical scavenger superoxide dismutase protected the reduced responsiveness to endothelium-dependent vasodilators following challenge. We conclude that ovalbumin challenge causes an abnormality in endothelial cell reactivity of pulmonary vasculature possibly due to destructive enzymes released from mast cells.

Selectivity profile of the α2-adrenoceptor antagonist efaroxan in relation to plasma glucose and insulin levels in the rat

The effects of efaroxan (RX 821037A; 2-[2-(2-ethyl-2,3-dihydrobenzofuranyl)]-2-imidazoline HCI) at α 1- and α 2-adrenoceptors were investigated in isolated tissues, pithed rats and conscious rats. In isolated tissues, efaroxan competitively antagonised the inhibitory effects of p-aminoclonidine in the electrically stimulated (0.1 Hz) rat vas deferens (pA 2 = 8.89) and the contractile effects of phenylephrine on the rat anococcygeus muscle (pA 2 = 6.03). Efaroxan had a selectivity ration ( α 2/ α 1) of 724 compared to a value of 182 for idazoxan. In pithed rats, the i.v. doses of efaroxan (μmol/kg) producing 2-fold shifts in dose-response curves for UK-14,304 at prejunctional cardiac α 2-adrenoceptors and postjunctional vascular α 2-adrenoceptors, and for cirazoline at postjunctional vascular α 1-adrenoceptors, were 0.05, 0.13 and 2.96, respectively. In conscious fasted rats, prazosin (5 mg/kg p.o.) increased resting glucose levels and exacerbated the hyperglycaemic effectsof UK-14,304 and adrenaline. In contrast, efaroxan (1–5 mg/kg p.o.) had little effect on resting plasma glucose but markedly antagonised the hyperglycaemic actions of UK-14,304 and adrenaline. Efaroxan increased resting plasma insulin levels and markedly potentiated the rise in insulin levels produced by adrenaline; this latter effect was prevented by the co-administration of propranolol. These results demonstrate that efaroxan is a potent and selective 2-adrenoceptor antagonist and provide further support for the involvement of α 2-adrenoceptors in glucose homeostasis.