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Query: UMLS:C0020538 (hypertension)
 170,190 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The major characteristic of renal hemodynamics in hypertension is abnormally high resistance of the preglomerular vessel, most likely the afferent arteriole (Af-Art). Although endothelium-derived relaxing factor (EDRF)/nitric oxide (NO) has been studied extensively in large vessels, little is known about its role in Af-Art reactivity. Using isolated microperfused Af-Arts of 12- to 13-week-old spontaneously hypertensive rats (SHRs) and their normotensive control, Wistar-Kyoto (WKY) rats, we examined the effect of acetylcholine (ACh) or N omega-nitro-L-arginine (L-NAME), which stimulates or blocks endothelium-derived NO, respectively. Af-Arts were preconstricted with norepinephrine to 70 +/- 5 and 62 +/- 4% of the control diameter in SHRs and WKY rats, respectively; the intraluminal pressure was kept at either 100 or 70 mm Hg. In SHRs, ACh (1 nM-0.1 mM) added to the Af-Art perfusate caused no vasodilation but tended to decrease the diameter further to 59 +/- 6% of control (N = 8). In contrast, in WKY rats, ACh reversed the luminal diameter to 90 +/- 4% of control (N = 6, p < 0.01 compared with SHRs). Contrary to the responses to ACh, blockade of endothelium-derived NO with L-NAME decreased the basal diameter by 31 +/- 8 and 14 +/- 5% in SHRs and WKY rats, respectively. We conclude that ACh-induced vasodilation is impaired in SHR Af-Art. The impaired response to ACh may be due to factors other than endothelium-derived NO such as endothelium-derived contracting factor (EDCF).
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PMID:Impaired response to acetylcholine despite intact endothelium-derived relaxing factor/nitric oxide in isolated microperfused afferent arterioles of the spontaneously hypertensive rat. 128 64

In uncomplicated essential hypertension, renal blood flow, glomerular filtration rate, and glomerular capillary pressure are within the normal range despite elevated renal perfusion pressure, suggesting abnormally high resistance of the preglomerular vessels. Among various preglomerular vascular segments, the afferent arteriole (Af-Art) is thought to be the site responsible for most resistance. However, little is known about the vascular reactivity of the Af-Art or its alteration in hypertension. In this study, we tested the hypothesis that pressure-induced constriction is exaggerated in Af-Arts from spontaneously hypertensive rats (SHRs). Single Af-Arts were microdissected from kidneys of SHRs and normotensive control Wistar-Kyoto (WKY) rats and were microperfused in vitro. When pressure in the Af-Art was increased stepwise from 20 to 80 mm Hg, luminal diameter increased similarly in both WKY and SHR Af-Arts (from 10.0 +/- 0.8 to 18.6 +/- 1.3 microns and from 10.1 +/- 1.2 to 16.9 +/- 1.5 microns, respectively). However, when pressure was further increased to 140 mm Hg, the diameter remained unchanged in WKY Af-Arts (19.2 +/- 1.9 microns), whereas it decreased significantly to 11.1 +/- 0.9 microns in those from SHRs. We conclude that pressure-induced constriction is exaggerated in SHR Af-Arts, which may contribute to the development and maintenance of hypertension.
Hypertension 1992 Feb
PMID:Pressure-induced constriction of the afferent arteriole of spontaneously hypertensive rats. 173 72

The World Hypertension League (WHL) International Art Competition started in 1991. The idea was to raise public awareness regarding hypertension prevention and treatment through unconventional means: Art. The purpose of this paper is to summarise the experience the WHL gained during preparation and follow-up activities of the Competition with emphasis on communication processes.
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PMID:Communicating through art: experience from the WHL Art Competition. 753 30

Delayed potentials (DP) (ECGHA) are markers of the occurrence of ventricular rhythm disturbances, and have a prognostic value after myocardial infarction. In hypertensive heart disease, the prevalence of DP is variable according to the literature (1-40%) and their prognostic significance is not known. We examine the frequency of DP in hypertension (HT) and the relationship between DP and left ventricular hypertrophy (LVH) as defined by echocardiographic estimation of the LV mass index (LVMI). We investigated 50 consecutive patients with essential HT who were being assessed as regards cause and effects of HT. Exclusion criteria were coronary artery disease, bundle branch block and poor echocardiographic trace. ECGHA was registered by means of ART device. The presence of DP as defined according to the criteria of Kacet. LV mass was determine according to the method of Penn and LVH defined according to the criteria of Devereux. Besides LVMI, were examined age, sex, duration of HT, micro-albuminuria, LVH on ECG (Sokolow index and strain-ECG). There were no correlations between the different variables studied and the presence of DP. The results relating to LVMI are shown in Table. There were no correlation between DP and LVH on echography. Other explanations, electrophysiologic, ischemic and histological may explain the greater incidence of BP observed in hypertensive heart disease. [table: see text] The prevalence of DP was not significantly different as regard the presence or absence of LVH (35% vs 25%; p = 0.53). In the 10 patients with the highest LVMI, the DP were enregistered 3 times.
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PMID:[Delayed potentials and left ventricular hypertrophy]. 812 12

Despite evidence that insulin per se may be an important regulator of glomerular hemodynamics, little is known about its direct action on the glomerular afferent arterioles (Af-Art) and efferent arterioles (Ef-Art), the crucial vascular segments that control glomerular hemodynamics. In the present study, we examined the direct effect of physiological concentrations of insulin on isolated microperfused rabbit Af- and Ef-Arts. After cannulation, vessels were equilibrated in insulin-free medium for 30 min. To determine whether insulin causes vasodilation or constriction, increasing doses (5, 20, and 200 microU/ml) were added to the bath and lumen of arterioles that were either preconstricted to 50% of control diameter with norepinephrine or left nonpreconstricted. Insulin caused no vasoconstriction in either Af- or Ef-Arts, but it reversed norepinephrine-induced constriction in Ef-Arts but not Af-Arts (suggesting a vasodilator action selective to the Ef-Art): at 200 microU/ml, insulin increased Ef-Art luminal diameter by 75.8 +/- 7.0% from the preconstricted level (n = 6; P < 0.008). The vasorelaxant effect of insulin on Ef-Arts was not affected by blockade of either endothelium-derived relaxing factor/nitric oxide or prostaglandin synthesis. Despite the lack of effect of insulin on Af-Art when added after the equilibration period, when Af-Arts were equilibrated in the presence of either 20 or 200 microU/ml insulin, their basal diameter was significantly reduced (11.7 +/- 0.9 microns; P < 0.025, n = 6, and 12.0 +/- 0.9 microns; P < 0.025, n = 7, respectively) compared with nontreated Af-Arts (16.2 +/- 1.3 microns; n = 7). In conclusion, this study demonstrates that at physiological concentrations, insulin dilates NE-constricted Ef-Arts, while insulin pretreatment enhances Af-Art tone. The disparate actions of insulin on the Af- vs the Ef-Art may contribute to its beneficial effect on glomerular hypertension.
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PMID:Disparate effects of insulin on isolated rabbit afferent and efferent arterioles. 840 51

A study of the effect of noise stress on some of the physiological parameters was carried out on healthy male workers of thermal power station (exposed to sound level 90-113 dBA) and compared with age and sex matched healthy controls (exposed to sound level 48-66 dBA). The parameters recorded were heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), galvanic skin resistance (GSR), auditory and visual reaction time (ART and VRT) and audiogram. Significant impairment in audiogram at 3000 Hz and 4000 Hz, increase in HR, SBP, DBP and decrease in GSR, ART and VRT were recorded in workers who were exposed to noise stress. Also a higher prevalence of hypertension was observed in them and that they were at a higher risk of developing hypertension than the control group. It was also observed that these modifications are related to duration of exposure to noise stress. It is presumed that all the above extra auditory effects are due to activation of autonomic nervous system and hypothalamo-hypophyseal adrenal axis, and the resultant release of catecholamines from adrenal medulla due to noise stress.
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PMID:Effect of noise stress on some cardiovascular parameters and audiovisual reaction time. 886 69

Renal vasoconstrictor action of angiotensin II (Ang II) is exaggerated in the spontaneously hypertensive rat (SHR) before development of hypertension. We have recently demonstrated that in the rabbit afferent arteriole (Af-Art) activation of the AT2 receptor causes vasodilation, which modulates the vasoconstrictor action of Ang II mediated by the AT1 receptor. In this study, we tested the hypothesis that vasoconstrictor action of Ang II is exaggerated in SHR Af-Arts due to an impaired function of the AT2 receptor before development of hypertension. Af-Arts were microdissected from the superficial cortex of 4- to 5-week-old SHR or age-matched Wistar Kyoto rats (WKY), and perfused at 60 mm Hg in vitro. Ang II (10(-11) to 10(-8) M) decreased the luminal diameter of Af-Arts of both strains in a dose-dependent manner. However, the constriction was stronger in SHR; at 10(-10) M, the diameter decreased by 34 +/- 4% in SHR (n = 6) compared to 18 +/- 3% in WKY (n = 6; p < 0.01). Pretreatment with PD123319 (PD), an AT2 receptor antagonist, significantly augmented Ang II-induced constriction in WKY but not SHR Af-Arts; at 10(-10) M, the diameter now decreased by 41 +/- 5 and 37 +/- 1% in SHR (n = 6) and WKY (n = 6), respectively. Thus, blockade of the AT2 receptor abolished the difference in Ang II action on Af-Arts between strains. Moreover, with the AT1 receptor blockade Ang II caused dose-dependent dilation of preconstricted Af-Arts only in WKY (27 +/- 5% at 10(-8) M, n = 5), and the dilation was abolished by simultaneous treatment with PD. In contrast, no such dilation was observed in SHR Af-Arts. These results suggest that activation of the AT2 receptor modulates AT1 receptor vasoconstriction in WKY Af-Arts, while impaired modulatory function of AT2 receptor may play a role in the exaggerated vasoconstrictor action of Ang II on the Af-Art of prehypertensive SHR.
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PMID:Vasodilation mediated by angiotensin II type 2 receptor is impaired in afferent arterioles of young spontaneously hypertensive rats. 985 67

Recent biological advances make it possible to discover new peptides associated with obesity. Leptin, neuropeptide Y, corticotrophin-releasing factor (CRF), alpha-melanocyte stimulating hormone (alpha-MSH), and cocaine- and amphetamine-regulated transcript (CART) peptides are known to participate in appetite and feeding behavior. Various lines of evidence suggest that these peptides participate not only in feeding behavior but also in cardiovascular and sympathetic regulations. Both leptin and ghrelin are secreted from the peripheral tissue; then they reach the brain to modulate sympathetic activity. These two peptides seem to play important roles to transmit peripheral metabolic information to the brain, and to convert it to cardiovascular and sympathetic information. Leptin activates neurons containing alpha-melanocyte stimulating hormone and cocaine- and amphetamine-regulated transcript peptides, resulting in increases in sympathetic activity and blood pressure. Cardiovascular action of alpha-melanocyte stimulating hormone is mediated through melanocortin-4 receptor, and agouti-related protein (AGRP) plays a role as an endogenous melanocortin-4 receptor antagonist. In contrast, ghrelin and neuropeptide Y in the brain suppress sympathetic activity and decrease blood pressure. Depressor and sympathoinhibitory effects of central neuropeptide Y are inhibited by leptin. Furthermore, central ghrelin modulates baroreflex control of renal sympathetic nerve activity and heart rate. Thus, leptin and the related peptides, which participate in appetite and feeding behavior, seem to function together to regulate cardiovascular system and sympathetic nerve activity, and may play a key role in the association between obesity and hypertension.
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PMID:Neural regulation of blood pressure by leptin and the related peptides. 1283 94

Dyslipidemia is now recognized as a significant potential adverse event in HIV-positive patients who are on ART. The tide of evidence continues to flow between the shore of HIV being the primary factor behind increased cardiovascular risk in HIV-positive patients, and the ocean of HAART being the primary cause. However, there clearly is an association between long-term infection with HIV and metabolic abnormalities. HIV-infected adults should undergo evaluation and treatment based on the NCEP ATP III guidelines. The NCEP recommends non-pharmacologic interventions be given a thorough trial prior to consideration of drug therapy. The recommendations also stipulate that intensive therapy with lipid-lowering medications should be used in individuals with metabolic syndrome. This includes aggressive treatment of hypertension, diabetes, and dyslipidemia. The NCEP also emphasizes the importance of smoking cessation, weight reduction, increased physical activity, and a salubrious diet. The fundamental message still is that physicians must treat HIV infection first. The choice of ART depends on many patient-specific factors, of which cardiovascular risk is only one.
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PMID:Cardiovascular risk among HIV-positive patients on antiretroviral therapy. 1456 35

The balance of vascular tone between afferent (Af-) and efferent arterioles (Ef-Arts) is a crucial determinant of glomerular hemodynamics. Thus, to understand renal physiology and pathophysiology it is important to study the mechanisms that control their vascular resistance. In order to directly study these mechanisms, we have developed several in vitro microperfusion preparations of these arterioles, which have the advantage of allowing us to observe the arteriolar diameter directly in the absence of systemic hemodynamic and hormonal influences. Using these preparations, we have found that angiotensin II (Ang II) causes much stronger constriction in Ef- than in Af-Arts and that this difference is mediated by nitric oxide (NO)- and prostaglandin (PG)-induced modulation of Ang II action in the Af-Art. We have also found that the vasoconstrictor effect of Ang II on Ef-Arts is modulated by PG produced by the upstream glomerulus. Thus, this may be a mechanism whereby the glomerulus controls its own capillary pressure by releasing PG and thereby adjusting the resistance of the downstream Ef-Art. In addition, we have found that in these arterioles activation of the Ang II type 2 (AT2) receptor causes endothelium-dependent vasodilation, which modulates the vasoconstrictor action mediated by its type 1 (AT1) receptors. Such modulator mechanisms that regulate Af- and Ef-Art tone may play an important role in the precise control of glomerular hemodynamics, and their alterations may play a role in the pathophysiology of renal diseases, including hypertension. Indeed, we have demonstrated that the vasoconstrictor action of Ang II on the Af-Art is exaggerated in spontaneously hypertensive rats, an animal model of human essential hypertension, due to an impaired function of the AT2 receptor before the development of hypertension. Because such exaggerated vasoconstriction leads to the elevation of renal vascular resistance (an important pathogenic factor for essential hypertension), our findings suggest that impaired function of the AT2 receptor in Af-Arts may play a role in the pathophysiology of essential hypertension.
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PMID:Role of angiotensin II and endogenous vasodilators in the control of glomerular hemodynamics. 1458 12


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