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Wistar rats resistant to the hypertensive effects of ouabain exhibit enhanced cardiac vagal activity and elevated plasma levels of calcitonin gene-related peptide.

ABSTRACT: Ouabain is a cardiac glycoside produced in the adrenal glands and hypothalamus. It affects the function of all cells by binding to Na+/K+-ATPase. Several lines of evidence suggest that endogenous ouabain could be involved in the pathogenesis of essential (particularly, salt-sensitive) hypertension. However, information regarding the postulated hypertensive effect of the long-term administration of low-dose exogenous ouabain is inconsistent. This study was designed to help settle this controversy through the use of telemetric monitoring of arterial blood pressure and to elucidate the ouabain-induced alterations that could either promote or prevent hypertension. Ouabain (63 and 324 µg/kg/day) was administered subcutaneously to male Wistar rats. Radiotelemetry was used to monitor blood pressure, heart rate and measures of cardiovascular variability and baroreflex sensitivity. The continuous administration of ouabain for 3 months did not elevate arterial blood pressure. The low-frequency power of systolic pressure variability, urinary excretion of catecholamines, and cardiovascular response to restraint stress and a high-salt diet as well as the responsiveness to ?1-adrenergic stimulation were all unaltered by ouabain administration, suggesting that the activity of the sympathetic nervous system was not increased. However, surrogate indices of cardiac vagal nerve activity based on heart rate variability were elevated. Molecular remodeling in mesenteric arteries that could support the development of hypertension (increased expression of the genes for the Na+/Ca2+ exchanger and Na+/K+-ATPase ?2 isoform) was not evident. Instead, the plasma level of vasodilatory calcitonin gene-related peptide (CGRP) significantly rose from 55 (11, SD) in the control group to 89 (20, SD) pg/ml in the ouabain-treated rats (PTukey's?=?18.10(-5)). These data show that long-term administration of exogenous ouabain does not necessarily cause hypertension in rodents. The augmented parasympathetic activity and elevated plasma level of CGRP could be linked to the missing hypertensive effect of ouabain administration.

SUBMITTER: Ghadhanfar E

PROVIDER: S-EPMC4184851 | biostudies-literature | 2014

REPOSITORIES: biostudies-literature

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Wistar rats resistant to the hypertensive effects of ouabain exhibit enhanced cardiac vagal activity and elevated plasma levels of calcitonin gene-related peptide.

Ghadhanfar Elham E Al-Bader Maie M Turcani Marian M

PloS one 20141003 10

Ouabain is a cardiac glycoside produced in the adrenal glands and hypothalamus. It affects the function of all cells by binding to Na+/K+-ATPase. Several lines of evidence suggest that endogenous ouabain could be involved in the pathogenesis of essential (particularly, salt-sensitive) hypertension. However, information regarding the postulated hypertensive effect of the long-term administration of low-dose exogenous ouabain is inconsistent. This study was designed to help settle this controversy ...[more]

PMID: 25279791

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Project description:Prolonged ouabain administration to normal rats causes sustained blood pressure (BP) elevation. This ouabain-induced hypertension (OH) has been attributed, in part, to the narrowing of third-order resistance arteries (approximately 320 microm internal diameter) as a result of collagen deposition in the artery media. Here we describe the structural and functional properties of fourth-order mesenteric small arteries from control and OH rats, including the effect of low-dose ouabain on myogenic tone in these arteries. Systolic BP in OH rats was 138 +/- 3 versus 124 +/- 4 mmHg in controls (P < 0.01). Pressurized (70 mmHg) control and OH arteries, with only a single layer of myocytes, both had approximately 165-microm internal diameters and approximately 20-microm wall thicknesses. Even after fixation, despite vasoconstriction, the diameters and wall thicknesses did not differ between control and OH fourth-order arteries, whereas in third-order arteries, both parameters were significantly smaller in OH than in controls. Myogenic reactivity was significantly augmented in OH fourth-order arteries. Nevertheless, phenylephrine- (1 microM) and high K(+)-induced vasoconstrictions and acetylcholine-induced vasodilation were comparable in control and OH arteries. Vasoconstrictions induced by 5 microM phenylephrine and by 10 mM caffeine in Ca(2+)-free media indicated that releasable sarcoplasmic reticulum Ca(2+) stores were normal in OH arteries. Importantly, 100 nM ouabain constricted both control and OH arteries by approximately 26 microm, indicating that this response was not downregulated in OH rats. This maximal ouabain-induced constriction corresponds to a approximately 90% increase in resistance to flow in these small arteries; thus ouabain at EC(50) of approximately 0.66 nM should raise resistance by approximately 35%. We conclude that dynamic constriction in response to circulating nanomolar ouabain in small arteries likely makes a major contribution to the increased vascular tone and BP in OH rats.

Project description:Periodontal disease (PD) is characterized by inflammation affecting the tissue surrounding the teeth, primarily affecting the soft tissues, like the gingiva. However, without proper treatment, the condition exacerbates and progresses to impact the deeper structures, as the alveolar bone. The periodontal inflammation leads to the alveolar bone resorption, that eventually results in the complete loss of tooth support. Given its potential consequences, periodontal disease is a significant public health concern, as one of the primary causes of tooth loss, contributing to issues such as impaired mastication, speech difficulties, low self-esteem, and quality of life. Notably, comorbidities, like hypertension, can exacerbate the progression and severity of periodontal disease. In addition, the coexistence of periodontal disease and hypertension is highly likely to occur due to sharing of several risk factors. A better understanding of the underling molecular mechanisms associated to the severity of periodontal disease in the context of hypertension would greatly contribute to the advancement of translational research in the field of periodontics. MicroRNAs, a class of small non-coding RNA molecules, have an important role in regulating gene expression at the post-transcriptional level. These molecules can regulate multiple mRNA targets through complementary base pairing between the miRNA 5' seed sequence and the mRNA 3' untranslated region (UTR). Therefore, microRNAs can potentially modulate a wide variety of cellular processes, in both normal and pathological contexts. Presently, most of the studies in the field concentrate on the periodontium soft tissues, while our understanding of microRNA modulation in the alveolar bone remains comparatively limited. We used microarray analysis to evaluate the expression profiles of microRNAs in the mandibles of Wistar and SHR rats with periodontal disease, compared to their respective control groups. Our aim was to identify microRNAs of interest that could possibly be associated to the periodontal disease-induced alveolar bone loss.

Dataset Information

Wistar rats resistant to the hypertensive effects of ouabain exhibit enhanced cardiac vagal activity and elevated plasma levels of calcitonin gene-related peptide.

Publications

Wistar rats resistant to the hypertensive effects of ouabain exhibit enhanced cardiac vagal activity and elevated plasma levels of calcitonin gene-related peptide.

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