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

We studied the heterogeneity of high-density lipoproteins (HDL) in plasma of 110 subjects, using three different methods: (a) gradient gel electrophoresis (GGE); (b) electroimmunoassay, to measure the concentration of lipoprotein particles containing apoprotein (apo) AI but no apo-AII (LP AI); and (c) cholesterol esterification rate (FERHDL) in very-low- and low-density lipoprotein-depleted plasma. There were two study groups: patients with hypertension, whose plasma lipid profile was similar to their respective controls, and patients with hypoalphalipoproteinemia (hypoalpha), whose family members served as controls. Values for FERHDL were significantly higher in both risk groups than in their respective controls. LP AI was significantly decreased only in the hypoalpha subjects. Generally, LP AI and FERHDL were inversely related. LP AI correlated strongly with plasma HDL-cholesterol, apo AI, and LP AI/AII; FERHDL correlated with those values inversely. LP AI, but not FERHDL, correlated with HDL free cholesterol. On the other hand, FERHDL correlated strongly with plasma concentrations of triglycerides and with the plasma ratio of total/HDL-cholesterol while LP AI did not. GGE determination of the composition of HDL subspecies showed that both FERHDL and LP AI were significantly related to the content of HDL2b particles: FERHDL inversely, LP AI directly; the relative amount of HDL3b,c particles correlated only with FERHDL. We conclude that GGE and FERHDL can be used to quantify both the apparently protective (HDL2b) and risk-associated (HDL3b,c) particles, whereas the concentration of LP AI in plasma mainly reflects the concentration of the HDL2 subpopulation.
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PMID:Structural and functional assessment of high-density lipoprotein heterogeneity. 788 38

In vivo tachyphylaxis to the angiotensin II-induced increase in mean arterial blood pressure was studied in conscious freely moving rats by telemetry blood pressure monitoring. The animals studied were the normotensive Sprague Dawley rats (SD), the spontaneously hypertensive rats (SHR), and two models of experimentally-induced hypertensive rats, namely, the left renal artery stenosed SD hypertensive rat (LRAS) and the deoxycorticosterone acetate/salt SD hypertensive rat (DOCA). Two consecutive dose-response curves to angiotensin II in each rat were obtained. The increase in mean arterial pressure (MAP) at each bolus dose of the first dose-response curve was found not to be significantly different from the corresponding value of the second dose-response curve in the four models of rat studied (i.e. no significant difference in the intra-rat response to AII). In addition, the slope of the dose-response curve is similar for each model of rat indicating that there was no inter-model variation to the response of AII. The results show that the response to AII in the SD and the three models of hypertensive rats was remarkably similar and that they did not develop tachyphylaxis to the pressor response of AII at concentrations ranging from circulating level of 0.0005 nmoles/kg (10(-11) M) to 10 nmoles/kg (2 x 10(-7) M). This was despite the fact that the SD had normal blood pressure and the genesis of hypertension in each model of the hypertensive rats was different.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:In vivo study of angiotensin II tachyphylaxis in freely moving normo- and hypertensive rats. 809 Jun 90

Starting from the structure of the novel nonpeptide AT1 receptor antagonist DuP 753 (losartan), a new series of potent antagonists was designed. In these compounds the central imidazole nucleus was replaced by the dihydroimidazol-4-one structure. The most active compounds had a spirocyclopentane or a spirocyclohexane ring in position 5. Like the imidazole series, the best substituents were the linear butyl chain in position 1 and the [2'-(tetrazol-5-yl)biphenylyl]methyl group in position 3. Antagonistic activity was assessed by the ability of the compounds to competitively inhibit [125I]AII binding to the AT1 subtype receptor and to antagonize AII-induced contractions in rabbit aorta rings. The most active compounds had IC50 values in the nanomolar range. In conscious rats, compounds 4 and 21 antagonized the AII pressor response when administered orally. Compound 21 (SR 47436) was the most active; it was recently shown to also be active in cynomolgus monkeys both intravenously and orally. This molecule is now undergoing clinical trials for the treatment of hypertension.
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PMID:A new series of imidazolones: highly specific and potent nonpeptide AT1 angiotensin II receptor antagonists. 823 Jan 27

A growing body of evidence suggests that angiotensin may have a functional role in growth and development, in addition to its classical role in the maintenance of body water homeostasis. Components of the renin-angiotensin system have been identified in the rat fetus. Because of the association between the renin-angiotensin system and hypertension, we quantified angiotensin receptor binding sites in the brains of spontaneously hypertensive rats (SHR) and Wistar Kyoto (WKY) rats during perinatal development. Using in vitro receptor autoradiography we identified specific 125I-Sar1,Ile8 AII binding in several areas of the brains of perinatal rats of both strains and observed significant differences in the concentration of binding sites, at different ages in several brain nuclei. With the knowledge that components of the renin-angiotensin system appear early in development and are known to have an association with cellular growth, it is possible that an irregularity in this system occurring during neurogenesis could contribute to developmental abnormalities, as well as subsequent hypertension.
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PMID:Differences between perinatal angiotensin binding in the brains of SHR and WKY rats. 835 5

The effect of angiotensin II-induced hypertension on tumor interstitial fluid pressure (TIFP) and tumor blood flow (TBF) was investigated to examine blood flow and pressure regulation in solid tumors. TIFP measurements were made before and after administration of angiotensin II using the wick-in-needle method in s.c. tumor implants. Relative TBF was continuously monitored by laser doppler velocimetry. The effect of host strain on TIFP was evaluated in MCA-IV mammary carcinoma, transplanted in C3H and SCID mice, and showed no significant difference. The effects of tumor types were evaluated by comparing two murine tumors, MCA-IV mammary carcinoma and FSaII fibrosarcoma, and a human tumor xenograft, LS174T adenocarcinoma, transplanted in SCID mice. Baseline TIFP was elevated in all three tumor lines to significantly different pressures. AII-induced hypertension (approximately 150 mm Hg) had a variable but tumor line-specific effect on TIFP and TBF. The increase in TIFP was correlated with the baseline TIFP (r2 = 0.853) (increasing from 6.9 to 8.7 mm Hg, 10.5 to 15.8 mm Hg, and 21.7 to 29.4 mm Hg in FSaII, MCA-IV, and LS174T, respectively). These data suggest that in addition to blood flow redistribution due to the steal phenomenon, arterial control of TBF and TIFP exists within these solid tumors; however, the extent of control is tumor line dependent and less than that in normal tissues. Moreover, parallel increases in TIFP and TBF do not support the hypothesis that elevated TIFP causes vascular collapse and thus decreases TBF.
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PMID:Effect of angiotensin II induced hypertension on tumor blood flow and interstitial fluid pressure. 849 5

ACEIs are widely prescribed antihypertensives and have become the mainstay of therapy for severe CHF. Nevertheless, a focused AII-receptor blockade has compelling intellectual appeal and substantial clinical advantages over the ACEIs (no disruption of the prostaglandin and bradykinin biosystems). Identification and careful characterization of the AII receptors and the recent discovery of their antagonists has led to the extensive clinical investigation of selective AII-receptor blockers in both hypertension and severe CHF. Studies with the first orally active AII-receptor blocker, losartan, have demonstrated safe and effective control of elevated blood pressure and improvement of the abnormal hemodynamics typical of pronounced CHF. Several other oral AII-receptor blockers are currently being evaluated, and early results with these agents are encouraging.
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PMID:Direct selective blockade of the vascular angiotensin II receptors in therapy for hypertension and severe congestive heart failure. 855 6

1. The role of the central renin-angiotensin system in the pathogenesis of hypertension in spontaneously hypertensive rats (SHR) was examined following acute and chronic intracerebroventricular (i.c.v.) infusions of angiotensin1 (AT1) receptor antagonists. 2. Groups of SHR were chronically instrumented for acute i.c.v. administration of the AT1 receptor antagonists, losartan and CV-11974, on mean arterial blood pressure (MAP) and heart rate (HR). Other groups of SHR also had mini-osmotic pumps implanted for chronic i.c.v. infusion of CV-11974. 3. Initially both young (15-18 weeks, n = 8) and old (25-29 weeks, n = 9) SHR received acute i.c.v. injections of losartan (10 micrograms) while a third group of young SHR received CV-11974 (1 microgram, n = 6). In all three groups of SHR, MAP and HR did not change up to 24 h after antagonist injection. However, changes in MAP and HR in response to i.c.v. angiotensin II (AII, 100 ng) were abolished 15 min after administration of the AT1 receptor antagonists. These responses had returned to control levels after 3 h in both groups given losartan but were still significantly depressed at 24 h in the CV-11974-treated group. By contrast, responses to i.v. AII (25 ng) before and 1 h after administration of AT1 receptor antagonists were not significantly different. 4. For chronic studies, four groups of SHR received chronic i.c.v. infusion of either vehicle (n = 9) or CV-11974 (1, 5 and 100 micrograms kg-1 day-1) (n = 4, 7 and 8 respectively) for 4 days. Baseline cardiovascular parameters were monitored daily together with changes in MAP and HR in response to both i.c.v. and i.v. AII (100 ng and 50 ng respectively) and i.v. phenylephrine (3 micrograms). Responses to i.c.v. carbachol (5 micrograms) were also recorded on day 4 while baroreflex function was assessed between days 1-3. In SHR treated chronically with i.c.v. vehicle or CV-11974, at 1 or 5 micrograms kg-1 day-1, resting MAP and HR did not vary over the four day infusion period. However, SHR treated with 100 micrograms kg-1 day-1 CV-11974 had significantly lower MAP compared to vehicle-treated SHR. While there was some variation in resting HR, there were no differences between the drug-treated and vehicle-treated groups. Pressor responses following i.c.v. AII administration were slightly, but significantly, inhibited on days 3 and 4 in the low dose CV-11974-treated (1 microgram kg-1 day-1) SHR. However, these responses were abolished on all 4 days in the 5 and 100 micrograms kg-1 day-1 CV-11974-treated groups. By contrast, changes in MAP and HR following i.v. AII injection did not vary over the 4 day infusion between SHR treated with the 2 lowest doses of CV-11974 and the vehicle-treated group. However, in the high dose CV-11974-treated SHR (100 micrograms kg-1 day-1), the cardiovascular effects of AII were abolished. In addition, phenylephrine (i.v.) and carbachol (i.c.v.) induced changes in MAP and HR were not significantly different in all four treatment groups. Similarly, baroreflex function was unaffected by i.c.v. infusion of 100 micrograms kg-1 day-1 CV-11974, except for a significant fall in BP50 which paralleled the fall in resting MAP. 5. Collectively, these results indicate that acute and chronic central AT1 receptor antagonism does not lower MAP in conscious SHR in doses which only block central AII-induced pressor activity. Chronic central infusion of CV-11974 at sufficiently high doses will lower MAP, as has been reported by others, but not without the abolition of the peripheral effects of AII. Therefore it is most likely that peripheral AT1 receptor blockade contributes to the hypotensive action of CV-11974 under these conditions.
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PMID:Lack of a centrally-mediated antihypertensive effect following acute or chronic central treatment with AT1-receptor antagonists in spontaneously hypertensive rats. 871 94

1. Male, vasopressin-deficient, normotensive (DI/N) and hypertensive (DI/H) rats were chronically instrumented (all surgery under sodium methohexitone anaesthesia) to allow assessment of resting haemodynamic status and responses to antagonism of AT1-receptors (Experiment 1), ET(A-) and ET(B-) receptors (Experiment 2) or adrenoceptors (Experiment 3). 2. Before any treatment, mean arterial blood pressure (MAP) was higher, and hindquarters vascular conductance was consistently lower in all groups of DI/H rats than in DI/N rats. 3. In Experiment 1, losartan (10 mg kg-1 i.v.), an AT1-receptor antagonist, was given 5 h after s.c. injection of saline, (DI/N, n = 8; DI/H, n = 8) or hyperoncotic polyethylene glycol, (DI/N, n = 9; DI/H, n = 9) to induce isosmotic hypovolaemia. In the volume-replete state, losartan caused similar small falls in MAP in the two groups (maximum delta MAP; DI/N, -9 +/- 2; DI/H, -15 +/- 5 mmHg), but the mesenteric and hindquarters vasodilatations were greater in DI/N rats. In the volume-depleted state the effects of losartan were augmented (delta MAP; DI/N, -32 +/- 3; DI/H. -31 +/- 3 mmHg), but its vasodilator effects were still greater in DI/N than in DI/H rats. 4. In Experiment 2, infusion of the ET(A-)ET(B-)receptor antagonist, SB 209670 (600 micrograms kg-1 h-1; DI/N, n = 8; DI/H, n = 9), had haemodynamic effects that were not different from those during saline infusion in DI/N (n = 7) and DI/H rats (n = 8). 5. In Experiment 3, sequential administration of the beta 2-adrenoceptor antagonist, ICI 118551 (0.2 mg kg-1 bolus, 0.1 mg kg-1 h-1 infusion), the alpha 2-adrenoceptor antagonist, idazoxan (0.75 mg kg-1 bolus, 1 mg kg-1 h-1 infusion), and losartan (10 mg kg-1 bolus) had only slight haemodynamic effects in DI/N (n = 8) and DI/H (n = 9) rats. Subsequent administration of the alpha 1-adrenoceptor antagonist, prazosin (0.5 mg kg-1 bolus, 0.8 mg kg-1 h-1 infusion) caused marked hypotension, although MAP was still higher in DI/H (95 +/- 4 mmHg) than in DI/N (75 +/- 4 mmHg) rats. However, in this circumstance there were no significant differences between renal, or mesenteric, or hindquarters vascular conductances in the two groups. 6. The results indicate that the hypertension and hindquarters vasoconstriction in DI/H rats is not dependent on AII or endothelin. Moreover, the relative elevation in MAP in DI/H persists in the presence of antagonism of beta 2, alpha 2- and alpha 1-adrenoceptors, in spite of no significant difference in regional vascular conductances.
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PMID:Regional haemodynamic effects of antagonists of angiotensin II, endothelin and adrenoceptors in conscious, vasopressin-deficient, genetically hypertensive rats. 873 34

Isolated hypoaldosteronism is found in 75% diabetics where the disease has persisted for 10 or more years. Sporadically it is found in congenital autonomous neuropathy, in acute glomerulonephritis, in gouty kidney, tubulointerstitial nephritis, after transplantation of the kidney, on mytomycin etc. During dynamic testing of the response of plasma renin activity and aldosterone to the administration of furosemide and a vertical position in diabetics a significantly reduced response was recorded as compared with non-diabetic hypertonic subjects. In 18.3% no response was observed (decompensated form of IHH). Diabetic hypertonics behaved like control hypertonics on long-term beta-blocker treatment. In the decompensated form of IHH after administration of drugs interfering with the activity of SNS-RAAS activity (ACEI, spirolactone etc.) a hyperkalaemic crisis may develop which threatens the patient with acidosis, dehydration, myoplegia, muscular spasms, however, in particular with fatal disorders of the cardiac rhythm. A similar effect may be exerted also by blockers of prostaglandin synthetase (non-steroid antirheumatics) and other drugs. The cause of IHH in diabetics is the coincidence of several pathogenic factors: 1. hypersecretion of ANF with hyperosmolar hyperglycaemic hypervolaemia and hyperfiltration already at the onset of DN, 2. early development of autonomous neuropathy of the sympathetic nerve, 3. reduced renin and prostaglandin formation already in the early stages of DN, 4. reduced extrarenal isorenin formation, 5. reduced conversion of prorenin into active renin, 6. reduced reactivity of the zona glomerulosa to AII, hyperkalaemia and ACTH for its functional reconstruction as a result of periodic activation of contraregulative hormones by fluctuations of the blood sugar level in diabetic patients, 7. reduced response of the distal renal tubule to aldosterone because of tubulointerstitial changes. IHH is thus another serious but rarely diagnosed late complication of diabetes which depends only partly on the stage of DN. It must be, however, diagnosed and respected with regard to the selection of drugs for the treatment of arterial hypertension and the syndrome of insulin resistance and the 5H syndrome resp., i.e. the association of hyperinsulinism which compensates insulin resistance with hyperglycaemia (NIDDM), hypertension, hyperlipoproteinaemia and hirsutism in women (so-called Stein-Leventhal syndrome).
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PMID:[Diabetic nephropathy and isolated hyporeninemic hypoaldosteronism]. 892 9

The basic clinical pathophysiology of primary aldosteronism (PAL) was described by Conn in terms of autonomous production of aldosterone, secondary suppression of renin and development of hypertension with hypokalaemic alkalosis. Conn recognised a normokalaemic form of the syndrome and suggested that it might masquerade as essential hypertension and be not uncommon. This was hotly disputed at the time, and normokalaemic PAL considered rare until recently, and, as a consequence, overlooked. The advent of a simple screening test, the aldosterone-renin ratio, led to recognition that normokalaemic forms are not uncommon. In fact, PAL may be the commonest specifically treatable and potentially curable form of hypertension so far identified. In all patients with PAL confirmed by lack of suppressibility ("autonomy") of aldosterone production, Familial Hyperaldosteronism Type I (FH-I, glucocorticoid-remediable hyperaldosteronism, reviewed elsewhere in this issue) should first be excluded by dexamethasone suppression or genetic testing. Capable of causing fatal stroke in young people affected by this dominantly inherited disorder, it can be reversed by doses of glucocorticoids such as dexamethasone which partially suppress endogenous ACTH without producing "steroid" side-effects. The remaining varieties of PAL may eventually also be shown to have a genetic basis, but are currently treated either by excision of a solitary aldosterone-secreting tumour or by antagonism of aldosterone's action in the renal tubule. It is possible that both adrenal cortices are genetically predisposed to overproduction of aldosterone in all varieties of PAL, whether because of anomalous regulation of aldosterone secretion or because of a tendency towards hyperplasia and neoplasia. Aldosterone-producing adenomas (APA's) can be divided into two main subtypes based on morphology and biochemical behaviour. The first subtype to be morphologically and biochemically characterised is composed predominantly of fasciculata-like cells and is unresponsive to angiotensin II (ALL-U-APA). The more recently characterised subtype is composed predominantly of glomerulosa-like cells, is responsive to angiotensin II (AII-R-APA) and could previously have been misdiagnosed as bilateral hyperplasia. The renin gene is often overexpressed in the second variety of adenoma, and in surrounding non-tumorous cortex, and the two subgroups show different allelic frequencies for RFLP's of the constitutive renin gene and the constitutive ANP gene locus. Unilateral, solitary, benign adrenal cortical adenomas producing aldosterone (APA's) represent a potentially surgically curable form of hypertension. Adrenal venous sampling (AVS) should always be performed because APA's are biochemically recognisable by adrenal venous steroid measurement before they are identifiable by computerised tomography or scintigraphy, and adrenal masses seen on CT may not be responsible for PAL. The secretory activity of adrenal masses must therefore be established by AVS before surgical removal. Discovery of an adrenal mass on CT requires formulation of a plan, whether or not it is found to be secreting hormones in excess. Independently of the treatment of the patient's hypertension, an apparently nonfunctioning adrenal mass ("incidentaloma") should be removed if 2.5 cm or more in diameter, because of the risk of cancer. Smaller masses require long-term follow-up. Primary aldosteronism not lateralising on AVS should be treated with low dose spironolactone, or with amiloride. For any such patients intolerant of medical treatment, laparoscopic removal of the adrenal showing higher production of aldosterone on AVS is an option worthy of consideration.The resultant reduction in mass of tissue autonomously secreting aldosterone should improve hypertension, as aldosterone productions falls below a critical level, and may even be curative in the short, medium or long term, depending on the rate of growth and activity of au
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PMID:Primary aldosteronism. 922 Dec 68


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