ABSTRACT
BACKGROUND: Reactive oxygen species (ROS), including those produced by NADPH oxidase (NOX), play an important vasomotor role, especially at early postnatal period. Mechanisms for regulating vascular tone can change significantly due to neonatal asphyxia and accompanying hypoxia. We tested the hypothesis that normobaric hypoxia (8% O2) for 2 h at the second day of life changes the functional contribution of NOX-derived ROS to the regulation of agonist-induced contraction in early postnatal rats. METHODS: We studied saphenous arteries from 11- to 14-day-old male offspring using isometric myography and Western blotting and assessed the content of biochemical parameters in blood serum. RESULTS: The values of main biochemical parameters in blood serum and the protein content of NOXs and superoxide dismutases in arterial tissue did not differ between "Control" and "Hypoxia" pups. The NOX inhibitor VAS2870 equally reduced the contractile responses of arteries to α1-adrenoceptor agonist methoxamine in "Control" and "Hypoxia" pups, but its effect was more pronounced in the arteries from "Hypoxia" pups when vasocontraction was evoked by the agonist of thromboxane A2 receptors U46619. CONCLUSION: Perinatal hypoxia at the second day of life increases procontractile influence of NOX-derived ROS to the regulation of U46619-induced vasocontraction in the systemic arteries at early postnatal ontogenesis. IMPACT: Nothing is known about programming effects of perinatal hypoxia, including birth asphyxia, on the ROS-mediated regulation of contraction in systemic arteries of early postnatal organism. 2-h normobaric hypoxia (8% O2) in rats at the second day of life increases the procontractile contribution of NOX-produced ROS to the regulation of U46619-induced vasocontraction in the systemic arteries at early postnatal ontogenesis. This fact may serve as a risk factor for the development of various disorders at later developmental stages and should be considered regarding the therapy for newborns who have suffered neonatal asphyxia.
ABSTRACT
Reactive oxygen species (ROS) produced by NADPH oxidases (NOX, a key source of ROS in vascular cells) are involved in the regulation of vascular tone, but this has been explored mainly for adult organisms. Importantly, the mechanisms of vascular tone regulation differ significantly in early postnatal ontogenesis and adulthood, while the vasomotor role of ROS in immature systemic arteries is poorly understood. We tested the hypothesis that the functional contribution of NADPH oxidase-derived ROS to the regulation of peripheral arterial tone is higher in the early postnatal period than in adulthood. We studied saphenous arteries from 10- to 15-day-old ("young") and 3- to 4-month-old ("adult") male rats using lucigenin-enhanced chemiluminescence, quantitative PCR, Western blotting, and isometric myography. We demonstrated that both basal and NADPH-stimulated superoxide anion radical (O2â¢-) production was significantly higher in the arteries from young in comparison to adult rats. Importantly, pan-inhibitor of NADPH oxidase VAS2870 (10 µM) reduced NADPH-induced O2â¢- production in arteries of young rats. Saphenous arteries of both young and adult rats demonstrated high levels of Nox2 and Nox4 mRNAs, while Nox1 and Nox3 mRNAs were not detected. The protein contents of NOX2 and NOX4 were significantly higher in arterial tissue of young compared to adult animals. Moreover, VAS2870 (10 µM) had no effect on methoxamine-induced contractile responses of adult arteries but decreased them significantly in young arteries; such effect of VAS2870 persisted after removal of the endothelium. Finally, NOX2 inhibitor GSK2795039 (10 µM), but not NOX1/4 inhibitor GKT137831 (10 µM) weakened methoxamine-induced contractile responses of arteries from young rats. Thus, ROS produced by NOX2 have a pronounced contractile influence in saphenous artery smooth muscle cells of young, but not adult rats, which is associated with the increased vascular content of NOX2 protein at this age.
Subject(s)
Arteries , NADPH Oxidases , Rats , Male , Animals , NADPH Oxidases/genetics , NADPH Oxidases/metabolism , Reactive Oxygen Species/metabolism , NADP , Methoxamine , Arteries/physiology , NADPH Oxidase 1/genetics , NADPH Oxidase 4/genetics , NADPH Oxidase 4/metabolism , Superoxides/metabolismABSTRACT
BACKGROUND: Perinatal hypoxia affects a lot of neonates worldwide every year, however its effects on the functioning of systemic circulation are not clear yet. We aimed at investigation the effects of perinatal hypoxia on the second day of life on the functioning of the rat systemic vasculature in early postnatal period. METHODS: 2-day-old male rat pups were exposed to normobaric hypoxia (8% O2, 92% N2) for 2 hours. At the 11-14 days cutaneous (saphenous) arteries were isolated and studied by wire myography and Western blotting. RESULTS: Hypoxia weakened the contribution of anticontractile influence of NO, but did not affect the contribution of Rho-kinase or Kv7 channels to the contraction to α1-adrenergic agonist methoxamine. The content of eNOS and protein kinase G were not altered by hypoxic conditions. CONCLUSION: Perinatal hypoxia in rats at the second day of life leads to the decrease of anticontractile effect of NO in the systemic arteries in early postnatal ontogenesis (at the age of 11-14 days). Decreased anticontractile effect of NO can be the reason for insufficient blood supply and represent a risk factor for the development of cardiovascular disorders. IMPACT: The mechanisms of perinatal hypoxia influences on systemic circulation are almost unknown. We have shown that perinatal hypoxia weakens anticontractile influence of nitric oxide in early postnatal period. The influence of perinatal hypoxia on systemic circulation should be taken into account during treatment of newborns suffered from the lack of oxygen.
Subject(s)
Animals, Newborn , Arteries , Hypoxia , Nitric Oxide , Animals , Nitric Oxide/metabolism , Male , Rats , Arteries/drug effects , Arteries/growth & development , Nitric Oxide Synthase Type III/metabolism , Vasoconstriction/drug effects , Rats, Wistar , Methoxamine/pharmacology , rho-Associated Kinases/metabolismABSTRACT
The study of the mechanisms of regulation of vascular tone is an urgent task of modern science, since diseases of the cardiovascular system remain the main cause of reduction in the quality of life and mortality of the population. Myography (isometric and isobaric) of isolated blood vessels is one of the most physiologically relevant approaches to study the function of cells in the vessel wall. On the one hand, cell-cell interactions as well as mechanical stretch of the vessel wall remain preserved in myography studies, in contrast to studies on isolated cells, e.g., cell culture. On the other hand, in vitro studies in isolated vessels allow control of numerous parameters that are difficult to control in vivo. The aim of this review was to 1) discuss the specifics of experimental design and interpretation of data obtained by myography and 2) highlight the importance of the combined use of myography with various complementary techniques necessary for a deep understanding of vascular physiology.
ABSTRACT
Introduction: Functional tests and training regimens intensity-controlled by an individual are used in sport practice, clinical rehabilitation, and space medicine. The model of voluntary wheel running in rats can be used to explore molecular mechanisms of such training regimens in humans. Respiratory and locomotor muscles demonstrate diverse adaptations to treadmill exercise, but the effects of voluntary exercise training on these muscle types have not been compared yet. Therefore, this work aimed at the effects of voluntary ET on rat triceps brachii and diaphragm muscles with special attention to reactive oxygen species, which regulate muscle plasticity during exercise. Methods: Male Wistar rats were distributed into exercise trained (ET) and sedentary (Sed) groups. ET group had free access to running wheels, running activity was continuously recorded and analyzed using the original hardware/software complex. After 8 weeks, muscle protein contents were studied using Western blotting. Results: ET rats had increased heart ventricular weights but decreased visceral/epididymal fat weights and blood triglyceride level compared to Sed. The training did not change corticosterone, testosterone, and thyroid hormone levels, but decreased TBARS content in the blood. ET rats demonstrated higher contents of OXPHOS complexes in the triceps brachii muscle, but not in the diaphragm. The content of SOD2 increased, and the contents of NOX2 and SOD3 decreased in the triceps brachii muscle of ET rats, while there were no such changes in the diaphragm. Conclusion: Voluntary wheel running in rats is intensive enough to govern specific adaptations of muscle fibers in locomotor, but not respiratory muscle.
ABSTRACT
Aim: TASK-1 channels are established regulators of pulmonary artery tone but their contribution to the regulation of vascular tone in systemic arteries is poorly understood. We tested the hypothesis that TASK-1 channel functional impact differs among systemic vascular beds, that this is associated with differences in their expression and may increase with alkalization of the extracellular environment. Therefore, we evaluated the expression level of TASK-1 channels and their vasomotor role in mesenteric and renal arteries. Methods: Pulmonary, mesenteric and renal arteries from male Wistar rats were used for TASK-1 channel mRNA (qPCR) and protein content (Western blotting) measurements. The functional role of TASK-1 channels was studied by wire myography using the TASK-1 channel blocker AVE1231. In some experiments, the endothelium was removed with a rat whisker. Results: Expression levels of both mRNA and protein of the TASK-1 channel pore-forming subunit were highest in pulmonary arteries, lowest in mesenteric arteries and had an intermediate value in renal arteries. Blockade of TASK-1 channels by 1 µM AVE1231 increased U46619-induced contractile responses of pulmonary arteries but did not affect basal tone and contractile responses to methoxamine of mesenteric and renal arteries at physiological extracellular pH (pHo = 7.41). At alkaline extracellular pH = 7.75 (increase of NaHCO3 to 52 mM) AVE1231 evoked the development of basal tone and increased contractile responses to low concentrations of methoxamine in renal but not mesenteric arteries. This effect was independent of the endothelium. Conclusion: In the rat systemic circulation, TASK-1 channels are abundant in renal arteries and have an anticontractile function under conditions of extracellular alkalosis.
ABSTRACT
The activity of many vasomotor signaling pathways strongly depends on extracellular/intracellular pH. Nitric oxide (NO) is one of the most important vasodilators produced by the endothelium. In this review, we present evidence that in most vascular beds of mature mammalian organisms metabolic or respiratory acidosis increases functional endothelial NO-synthase (eNOS) activity, despite the observation that direct effects of low pH on eNOS enzymatic activity are inhibitory. This can be explained by the fact that acidosis increases the activity of signaling pathways that positively regulate eNOS activity. The role of NO in the regulation of vascular tone is greater in early postnatal ontogenesis compared to adulthood. Importantly, in early postnatal ontogenesis acidosis also augments functional eNOS activity and its contribution to the regulation of arterial contractility. Therefore, the effect of acidosis on total peripheral resistance in neonates may be stronger than in adults and can be one of the reasons for an undesirable decrease in blood pressure during neonatal asphyxia. The latter, however, should be proven in future studies.
Subject(s)
Acidosis , Endothelium, Vascular , Acidosis/metabolism , Adult , Animals , Blood Pressure , Endothelium, Vascular/metabolism , Humans , Infant, Newborn , Mammals/metabolism , Nitric Oxide/metabolism , Nitric Oxide Synthase Type III/metabolism , Vasodilator Agents/pharmacologyABSTRACT
BACKGROUND: Antenatal/early postnatal hypothyroidism weakens NO-mediated anticontractile influence of endothelium in coronary arteries of adult rats, but it remains unclear whether this occurs in other vascular regions. We hypothesized that developmental thyroid deficiency is followed by region-specific changes in the endothelial NO-pathway activity in systemic vasculature. To explore this, we estimated the effects of antenatal/early postnatal hypothyroidism on NO-pathway activity and its potential local control mechanisms in rat mesenteric and skeletal muscle (sural) arteries. METHODS: Dams were treated with 6-propyl-2-thiouracil (PTU) in drinking water (0.0007%) during pregnancy and 2 weeks postpartum; control (CON) females received PTU-free water. Adult offspring (10-12-weeks) arteries were studied by wire myography, qPCR, and Western blotting. RESULTS: Endothelium removal or inhibition of NO-synthase with L-NNA augmented contractile responses to α1-adrenoceptor agonist methoxamine. In PTU compared to CON group, these effects were stronger in sural arteries, but did not differ in mesenteric arteries. The responses of both arteries to NO-donor DEA/NO were similar in CON and PTU rats. mRNA contents of deiodinase 2 and thyroid hormone receptor α were similar in mesenteric arteries of two groups but were elevated in sural arteries of PTU group compared to CON. The abundance of eNOS protein was higher in sural arteries of PTU compared to CON rats. CONCLUSION: Antenatal/early postnatal hypothyroidism is followed by an increase in NO-mediated anticontractile influence in sural, but not in mesenteric arteries of adult animals. The diversity of hypothyroidism effects may be due to different alterations of local T3 synthesis/reception in different vascular beds.
ABSTRACT
Nitric oxide (NO) has been shown to stimulate differentiation and increase the survival of ganglionic sympathetic neurons. The proportion of neuronal NOS-immunoreactive sympathetic preganglionic neurons is particularly high in newborn rats and decreases with maturation. However, the role of NO in the development of vascular sympathetic innervation has never been studied before. We tested the hypothesis that intrauterine NO deficiency weakened the development of vascular sympathetic innervation and thereby changed the contractility of peripheral arteries and blood pressure level in two-week-old offspring. Pregnant rats consumed NOS inhibitor L-NAME (250 mg/L in drinking water) from gestational day 10 until delivery. Pups in the L-NAME group had a reduced body weight and blood level of NO metabolites at 1-2 postnatal days. Saphenous arteries from two-week-old L-NAME offspring demonstrated a lower density of sympathetic innervation, a smaller inner diameter, reduced maximal active force and decreased α-actin/ß-actin mRNA expression ratio compared to the controls. Importantly, pups in the L-NAME group exhibited decreased blood pressure levels before, but not after, ganglionic blockade with chlorisondamine. In conclusion, intrauterine L-NAME exposure is followed by the impaired development of the sympathetic nervous system in early postnatal life, which is accompanied by the structural and functional remodeling of arterial blood vessels.
Subject(s)
Arteries/innervation , Enzyme Inhibitors/pharmacology , NG-Nitroarginine Methyl Ester/pharmacology , Nitric Oxide Synthase/antagonists & inhibitors , Sympathetic Nervous System/embryology , Sympathetic Nervous System/growth & development , Vascular Remodeling/drug effects , Animals , Animals, Newborn , Arteries/metabolism , Blood Pressure/drug effects , Body Weight/drug effects , Female , Gestational Age , Male , Models, Animal , Nitric Oxide/metabolism , Nitric Oxide Synthase/metabolism , Pregnancy , Rats , Rats, Wistar , Sympathetic Nervous System/metabolismABSTRACT
Aim: Hyperthyroidism is associated with a decreased peripheral vascular resistance, which could be caused by the vasodilator genomic or non-genomic effects of thyroid hormones (TH). Non-genomic, or acute, effects develop within several minutes and involve a wide tissue-specific spectrum of molecular pathways poorly studied in vasculature. We aimed to investigate the mechanisms of acute effects of TH on rat skeletal muscle arteries. Methods: Sural arteries from male Wistar rats were used for isometric force recording (wire myography) and phosphorylated protein content measurement (Western blotting). Results: Both triiodothyronine (T3) and thyroxine (T4) reduced contractile response of sural arteries to α1-adrenoceptor agonist methoxamine. The effect of T4 was more prominent than T3 and not affected by iopanoic acid, an inhibitor of deiodinase 2. Endothelium denudation abolished the effect of T3, but not T4. Integrin αvß3 inhibitor tetrac abolished the effect of T4 in endothelium-denuded arteries. T4 weakened methoxamine-induced elevation of phospho-MLC2 (Ser19) content in arterial samples. The effect of T4 in endothelium-denuded arteries was abolished by inhibiting ERK1/2 activation with U0126 as well as by ILK inhibitor Cpd22 but persisted in the presence of Src- or Rho-kinase inhibitors (PP2 and Y27632, respectively). Conclusion: Acute non-genomic relaxation of sural arteries induced by T3 is endothelium-dependent and that induced by T4 is endothelium-independent. The effect of T4 on α1-adrenergic contraction is stronger compared to T3 and involves the suppression of extracellular matrix signaling via integrin αvß3, ERK1/2 and ILK with subsequent decrease of MLC2 (Ser19) phosphorylation.
ABSTRACT
Nitric oxide (NO) deficiency during pregnancy is a key reason for preeclampsia development. Besides its important vasomotor role, NO is shown to regulate the cell transcriptome. However, the role of NO in transcriptional regulation of developing smooth muscle has never been studied before. We hypothesized that in early ontogeny, NO is important for the regulation of arterial smooth muscle-specific genes expression. Pregnant rats consumed NO-synthase inhibitor L-NAME (500 mg/L in drinking water) from gestational day 10 till delivery, which led to an increase in blood pressure, a key manifestation of preeclampsia. L-NAME reduced blood concentrations of NO metabolites in dams and their newborn pups, as well as relaxations of pup aortic rings to acetylcholine. Using qPCR, we demonstrated reduced abundances of the smooth muscle-specific myosin heavy chain isoform, α-actin, SM22α, and L-type Ca2+-channel mRNAs in the aorta of newborn pups from the L-NAME group compared to control pups. To conclude, the intrauterine NO deficiency weakens gene expression specific for a contractile phenotype of arterial smooth muscle in newborn offspring.
Subject(s)
Cell Differentiation , Muscle, Smooth, Vascular/metabolism , Nitric Oxide/deficiency , Pregnancy Complications/metabolism , Uterus/metabolism , Animals , Animals, Newborn , Female , Gene Expression Regulation , Muscle Proteins/biosynthesis , Muscle, Smooth, Vascular/pathology , NG-Nitroarginine Methyl Ester/pharmacology , Nitric Oxide/metabolism , Pregnancy , Pregnancy Complications/chemically induced , Pregnancy Complications/pathology , Rats , Rats, Wistar , Uterus/pathologyABSTRACT
Intrauterine growth restriction (IUGR) is one of the most common pathologies of pregnancy. The cardiovascular consequences of IUGR do not disappear in adulthood and can manifest themselves in pathological alterations of vasomotor control. The hypothesis was tested that IUGR weakens anticontractile influence of NO and augments procontractile influence of Rho-kinase in arteries of adult offspring. To model IUGR in the rat, dams were 50% food restricted starting from the gestational day 11 till delivery. Mesenteric and coronary arteries of male offspring were studied at the age of 3 months using wire myography, qPCR, and Western blotting. Contractile responses of mesenteric arteries to α1-adrenoceptor agonist methoxamine as well as influences of NO and Rho-kinase did not differ between control and IUGR rats. However, coronary arteries of IUGR rats demonstrated elevated contraction to thromboxane A2 receptor agonist U46619 due to weakened anticontractile influence of NO and enhanced role of Rho-kinase in the endothelium. This was accompanied by reduced abundance of SODI protein and elevated content of RhoA protein in coronary arteries of IUGR rats. IUGR considerably changes the regulation of coronary vascular tone in adulthood and, therefore, can serve as a risk factor for the development of cardiac disorders.
Subject(s)
Coronary Vessels/physiopathology , Fetal Growth Retardation/etiology , Mesenteric Arteries/physiopathology , Nitric Oxide/metabolism , 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid/pharmacology , Amides/pharmacology , Animals , Disease Models, Animal , Female , Male , Mesenteric Arteries/drug effects , Muscle Contraction , Nitric Oxide Synthase Type III/metabolism , Pregnancy , Pyridines/pharmacology , Rats, Wistar , rho-Associated Kinases/antagonists & inhibitorsABSTRACT
Previously, the abundance of p42/44 and p38 MAPK proteins had been shown to be higher in arteries of 1- to 2-week-old compared to 2- to 3-month-old rats. However, the role of MAPKs in vascular tone regulation in early ontogenesis remains largely unexplored. We tested the hypothesis that the contribution of p42/44 and p38 MAPKs to the contraction of peripheral arteries is higher in the early postnatal period compared to adulthood. Saphenous arteries of 1- to 2-week-old and 2- to 3-month-old rats were studied using wire myography and western blotting. The α1-adrenoceptor agonist methoxamine did not increase the phosphorylation level of p38 MAPK in either 1- to 2-week-old or 2- to 3-month-old rats. Accordingly, inhibition of p38 MAPK did not affect arterial contraction to methoxamine in either age group. Methoxamine increased the phosphorylation level of p42/44 MAPKs in arteries of 2- to 3-month-old and of p44 MAPK in 1- to 2-week-old rats. Inhibition of p42/44 MAPKs reduced methoxamine-induced contractions in arteries of 2- to 3-month-old, but not 1- to 2-week-old rats. Thus, despite a high abundance in arterial tissue, p38 and p42/44 MAPKs do not regulate contraction of the saphenous artery in the early postnatal period. However, p42/44 MAPK activity contributes to arterial contractions in adult rats.
Subject(s)
Mitogen-Activated Protein Kinase 1/genetics , Mitogen-Activated Protein Kinase 3/genetics , Muscle Contraction/genetics , Receptors, Adrenergic, alpha-1/genetics , p38 Mitogen-Activated Protein Kinases/genetics , Animals , Arteries/growth & development , Arteries/metabolism , Embryo, Mammalian , Embryonic Development/genetics , Humans , Methoxamine/pharmacology , Muscle Contraction/drug effects , Muscle, Smooth/metabolism , Phosphorylation/drug effects , RatsABSTRACT
Maturation of the cardiovascular system is associated with crucial structural and functional remodeling. Thickening of the arterial wall, maturation of the sympathetic innervation, and switching of the mechanisms of arterial contraction from calcium-independent to calcium-dependent occur during postnatal development. All these processes promote an almost doubling of blood pressure from the moment of birth to reaching adulthood. This review focuses on the developmental alterations of potassium channels functioning as key smooth muscle membrane potential determinants and, consequently, vascular tone regulators. We present evidence that the pattern of potassium channel contribution to vascular control changes from Kir2, Kv1, Kv7 and TASK-1 channels to BKCa channels with maturation. The differences in the contribution of potassium channels to vasomotor tone at different stages of postnatal life should be considered in treatment strategies of cardiovascular diseases associated with potassium channel malfunction.
Subject(s)
Arteries/metabolism , Myocytes, Smooth Muscle/metabolism , Potassium Channels/metabolism , Animals , Blood Pressure/physiology , Calcium/metabolism , Membrane Potentials/physiology , Muscle, Smooth, Vascular/metabolism , Postnatal Care/methodsABSTRACT
Membrane transporters and their functional contribution in vasculature change during early postnatal development. Here we tested the hypothesis that the contribution of Cl- channels to arterial contraction declines during early postnatal development and this decline is associated with the trophic sympathetic influence. Endothelium-denuded saphenous arteries from 1- to 2-week-old and 2- to 3-month-old male rats were used. Arterial contraction was assessed in the isometric myograph, in some experiments combined with measurements of membrane potential. mRNA and protein levels were determined by qPCR and Western blot. Sympathectomy was performed by treatment with guanethidine from the first postnatal day until 8-9-week age. Cl- substitution in the solution as well as Cl--channel blockers (MONNA, DIDS) had larger suppressive effect on the methoxamine-induced arterial contraction and methoxamine-induced depolarization of smooth muscle cells in 1- to 2-week-old compared to 2- to 3-month-old rats. Vasculature of younger group demonstrated elevated expression levels of TMEM16A and bestrophin 3. Chronic sympathectomy increased Cl- contribution to arterial contraction in 2-month-old rats that was associated with an increased TMEM16A expression level. Our study demonstrates that contribution of Cl- channels to agonist-induced arterial contraction and depolarization decreases during postnatal development. This postnatal decline is associated with sympathetic nerves development.
Subject(s)
Arteries/metabolism , Chloride Channels/metabolism , Muscle Contraction/physiology , Sympathetic Nervous System/metabolism , Animals , Anoctamin-1/metabolism , Arteries/drug effects , Male , Methoxamine/pharmacology , Muscle Contraction/drug effects , Muscle, Smooth, Vascular/drug effects , Muscle, Smooth, Vascular/metabolism , Muscle, Smooth, Vascular/physiology , Myocytes, Smooth Muscle/drug effects , Myocytes, Smooth Muscle/metabolism , Myocytes, Smooth Muscle/physiology , Rats , Rats, Wistar , Sympathectomy/methods , Sympathetic Nervous System/drug effects , Sympathetic Nervous System/physiology , Vasoconstriction/drug effects , Vasoconstriction/physiologyABSTRACT
BACKGROUND AND PURPOSE: The vasomotor role of K2P potassium channels during early postnatal development has never been investigated. We tested the hypothesis that TASK-1 channel (K2P family member) contribution to arterial vascular tone and BP is higher in the early postnatal period than in adulthood. EXPERIMENTAL APPROACH: We studied 10- to 15-day-old ("young") and 2- to 3-month-old ("adult") male rats performing digital PCR (dPCR) (using endothelium-intact saphenous arteries), isometric myography, sharp microelectrode technique, quantitative PCR (qPCR) and Western blotting (using endothelium-denuded saphenous arteries), and arterial pressure measurements under urethane anaesthesia. KEY RESULTS: We found mRNA of Kcnk1-Kcnk7, Kcnk12, and Kcnk13 genes to be expressed in rat saphenous artery, and Kcnk3 (TASK-1) and Kcnk6 (TWIK-2) were most abundant in both age groups. The TASK-1 channel blocker AVE1231 (1 µmol·L-1 ) prominently depolarized arterial smooth muscle and increased basal tone level and contractile responses to methoxamine of arteries from young rats but had almost no effect in adult rats. The level of TASK-1 mRNA and protein expression was higher in arteries from young compared with adult rats. Importantly, intravenous administration of AVE1231 (4 mg·kg-1 ) had no effect on mean arterial pressure in adult rats but prominently raised it in young rats. CONCLUSION AND IMPLICATIONS: We showed that TASK-1 channels are important for negative feedback regulation of vasocontraction in young but not adult rats. The influence of TASK-1 channels most likely contributes to low BP level at perinatal age.
Subject(s)
Arteries , Muscle, Smooth, Vascular , Animals , Female , Male , Methoxamine , Myography , Nerve Tissue Proteins , Potassium Channels , Potassium Channels, Tandem Pore Domain , Pregnancy , RatsABSTRACT
BACKGROUND: Voltage-gated potassium (Kv) channels, especially Kv7 channels, are major potassium channels identified in vascular smooth muscle cells with a great, albeit differential functional impact in various vessels. Vascular smooth muscle Kv7 channels always coexist with other K channels, in particular with BK channels. BK channels differ in the extent to which they influence vascular contractility. Whether this difference also causes the variability in the functional impact of Kv7 channels is unknown. Therefore, this study addressed the hypothesis that the functional impact of Kv7 channels depends on BK channels. EXPERIMENTAL APPROACH: Experiments were performed on young and adult rat gracilis and saphenous arteries using real-time PCR as well as pressure and wire myography. KEY RESULTS: Several subfamily members of Kv7 (KCNQ) and BK channels were expressed in saphenous and gracilis arteries: the highest expression was observed for BKα, BKß1 and KCNQ4. Arterial contractility was assessed with methoxamine-induced contractions and pressure-induced myogenic responses. In vessels of adult rats, inhibition of Kv7 channels or BK channels by XE991 or IBTX, respectively enhanced arterial contractility to a similar degree, whereas activation of Kv7 channels or BK channels by retigabine or NS19504, respectively reduced arterial contractility to a similar degree. Further, IBTX increased both the contractile effect of XE991 and the anticontractile effect of retigabine, whereas NS19504 reduced the effect of retigabine and impaired the effect of XE991. In vessels of young rats, inhibition of Kv7 channels by XE991 enhanced arterial contractility much stronger than inhibition of BK channels by IBTX, whereas activation of Kv7 by retigabine reduced arterial contractility to a greater extent than activation of BK channels by NS19504. Further, IBTX increased the anticontractile effect of retigabine but not the contractile effect of XE991, whereas NS19504 reduced the effect of retigabine and impaired the effect of XE991. CONCLUSION: Kv7 and BK channels are expressed in young and adult rat arteries and function as negative feedback modulators in the regulation of contractility of these arteries. Importantly, BK channels govern the extent of functional impact of Kv7 channels. This effect depends on the relationship between the functional activities of BK and Kv7 channels.
ABSTRACT
Nitric oxide (NO) produced in the wall of blood vessels is necessary for the regulation of vascular tone to ensure an adequate blood supply of organs and tissues. In this review, we present evidence that the functioning of endothelial NO-synthase (eNOS) changes considerably during postnatal maturation. Alterations in NO-ergic vasoregulation in early ontogeny vary between vascular beds and correlate with the functional reorganization of a particular organ. Importantly, the anticontractile effect of NO can be an important mechanism responsible for the protectively low blood pressure in the immature circulatory system. The activity of eNOS is regulated by a number of hormones, including thyroid hormones which are key regulators of the perinatal developmental processes. Maternal thyroid hormone deficiency suppresses the anticontractile effect of NO at perinatal age. Such alterations disturb perinatal cardiovascular homeostasis and lead to delayed occurring cardiovascular pathologies in adulthood. The newly discovered role of thyroid hormones may have broad implications in cardiovascular medicine, considering the extremely high prevalence of maternal hypothyroidism in human society.
Subject(s)
Blood Vessels/physiology , Endothelium, Vascular/physiology , Neovascularization, Physiologic , Nitric Oxide/biosynthesis , Animals , Biomarkers , Blood Circulation , Humans , Nitric Oxide Synthase Type III/genetics , Nitric Oxide Synthase Type III/metabolism , Thyroid Hormones/metabolismABSTRACT
NEW FINDINGS: What is the topic of this review? This symposium report discusses the previously unrecognized pro-contractile role of chloride ions in rat arteries at early stages of postnatal development. What advances does it highlight? It highlights the postnatal decline in the contribution of chloride ions to regulation of arterial contractile responses and potential trophic role of sympathetic nerves in these developmental alterations. ABSTRACT: Chloride ions are important for smooth muscle contraction in adult vasculature. Arterial smooth muscle undergoes structural and functional remodelling during early postnatal development, including changes in K+ currents, Ca2+ handling and sensitivity. However, developmental change in the contribution of Cl- to regulation of arterial contraction has not yet been explored. Here, we provide the first evidence that the role of Cl- in α1 -adrenergic arterial contraction prominently decreases during early postnatal ontogenesis. The trophic influence of sympathetic nerves is a potential mechanism for postnatal decline of the contribution of Cl- to the vascular contraction.
Subject(s)
Adrenergic Fibers/physiology , Chlorides/physiology , Endothelium, Vascular/physiology , Muscle, Smooth, Vascular/physiology , Vasoconstriction/physiology , Vasoconstrictor Agents/pharmacology , Adrenergic Fibers/drug effects , Animals , Endothelium, Vascular/drug effects , Endothelium, Vascular/innervation , Humans , Muscle, Smooth, Vascular/drug effects , Muscle, Smooth, Vascular/innervation , Vasoconstriction/drug effectsABSTRACT
AIM: Potassium channels are key regulators of smooth muscle membrane potential and arterial tone. However, the roles of potassium channels in vascular tone regulation in the systemic circulation during early postnatal development are poorly understood. Therefore, this study tested the hypothesis that the negative feedback regulation of vasocontraction by potassium channels changes during maturation. METHODS: Experiments were performed on endothelium-denuded saphenous arteries from 10- to 15-day-old and 2- to 3-month-old male rats. Isometric force and membrane potential were recorded using wire myography and the sharp microelectrode technique respectively; mRNA and protein contents were determined by qPCR and Western blotting. RESULTS: The effects of Kv 1, Kir and Kv 7 channel blockers (DPO-1, BaCl2 , XE991) on methoxamine-induced contraction were larger in arteries of 10- to 15-day-old compared to 2- to 3-month-old animals. In contrast, the BKCa channel blocker iberiotoxin had a stronger influence in 2- to 3- month-old rats. The effects of KATP and Kv 2 channel blockers (glibenclamide, stromatoxin) were not pronounced at both ages. The larger influence of Kv 7 and Kir channel blockade on arterial contraction in 10- to 15-day-old rats was associated with more prominent smooth muscle depolarization. The developmental alterations in potassium channel functioning were generally consistent with their mRNA and protein expression levels in arterial smooth muscle. CONCLUSION: The negative feedback regulation of vasocontraction by potassium channels varies during maturation depending on the channel type. A dominating contribution of Kv 7 channels to the regulation of basal tone and agonist-induced contraction was observed in arteries of 10- to 15-day-old animals.