Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0020538 (hypertension)
 170,190 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Sodium homeostasis is crucial for the control of extra-cellular volume and blood pressure. Regulation of sodium reabsorption is mainly achieved in the distal nephron by the mineralocorticoid aldosterone, but the molecular pathway of aldosterone action has largely remained unclear. Molecular genetic analysis of inherited diseases disturbing sodium homeostasis has now demonstrated that the amiloride-sensitive epithelial sodium channel is a major effector of aldosterone action. Mechanisms by which aldosterone regulates the epithelial sodium channel activity are beginning to emerge and will be of great importance for a better understanding of salt-sensitive hypertension.
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PMID:A reappraisal of aldosterone effects on the kidney: new insights provided by epithelial sodium channel cloning. 905 52

Liddle's syndrome is an autosomal dominant form of hypertension that resembles primary hyperaldosteronism, is characterized by the early onset of hypertension with hypokalemia and suppression of both PRA and aldosterone, and is caused by mutations in the carboxyl-terminus of the beta- or gamma-subunits of the renal epithelial sodium channel. We describe a kindred (K176) whose distinguishing clinical features were mild hypertension and decreased aldosterone secretion. The index case was a 16-yr-old girl with intermittent mild hypertension and hypokalemia and subnormal PRA, aldosterone, 18-hydroxy-corticosterone, and deoxycortisol levels, but normal cortisol/cortisone metabolite ratio and cortisol half-life. A frameshift mutation in the carboxyl-terminus of the beta-subunit of the epithelial sodium channel was identified in the index case, establishing the diagnosis of Liddle's syndrome. Sixteen at-risk relatives of the index case were tested. Seven new subjects were heterozygous for the mutation found in the index case, and two deceased obligate carriers were identified. All genetically affected adult subjects had a history of mild hypertension, and four had a history of hypokalemia. Basal and postcosyntropin plasma aldosterone and urinary aldosterone levels were significantly suppressed in those positive for the mutation. The family demonstrates variability in the severity of hypertension and hypokalemia in this disease, raising the possibility that this disease may be underdiagnosed among patients with essential hypertension.
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PMID:Liddle's syndrome: prospective genetic screening and suppressed aldosterone secretion in an extended kindred. 910 May 75

In the most exciting genetic advances in the diagnosis of essential hypertension, genes responsible for three distinct forms of low-renin hypertension have been identified. Two of these forms are dominant: glucocorticoid remediable hypertension (a new gene created by the fusion of the 11 beta-hydroxylase and aldosterone synthase genes) and Liddle's syndrome (a defect in the epithelial sodium channel). One of the forms is recessive: the syndrome of apparent mineralocorticoid excess (a defect in renal 11 beta-hydroxysteroid dehydrogenase). The role of more than 20 other genes in causing hypertension has been assessed with variable findings. The most convincing evidence supports a role for the angiotensinogen gene, where linkage has been documented and an association with an intermediate phenotype of hypertension (nonmodulation) has been reported.
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PMID:Genetic approach to diagnostic and therapeutic decisions in human hypertension. 914 79

The relative importance of molecular biology in clinical practice is often underestimated. However, numerous procedures in clinical diagnosis and new therapeutic drugs have resulted from basic molecular research. Furthermore, understanding of the physiological and physiopathological mechanisms underlying several human diseases has been improved by the results of basic molecular research. For example, cloning of the gene encoding leptin has provided spectacular insights into the understanding of the mechanisms involved in the control of food intake and body weight maintenance in man. In cystic fibrosis, the cloning and identification of several mutations in the gene encoding the chloride channel transmembrane regulator (CFTR) have resolved several important issues in clinical practice: cystic fibrosis constitutes a molecular defect of a single gene. There is a strong correlation between the clinical manifestations or the severity of the disease (phenotype) with the type of mutations present in the CFTR gene (genotype). More recently, identification of mutations in the gene encoding a subunit of the renal sodium channel in the Liddle syndrome has provided important insight into the physiopathological understanding of mechanisms involved in this form of hereditary hypertension. Salt retention and secondary high blood pressure are the result of constitutive activation of the renal sodium channel by mutations in the gene encoding the renal sodium channel. It is speculated that less severe mutations in this channel could result in a less severe form of hypertension which may correspond to patients suffering from high blood pressure with low plasma renin activity. Several tools, most notably PCR, are derived from molecular research and are used in everyday practice, i.e. in prenatal diagnosis and in the diagnosis of several infectious diseases including tuberculosis and hepatitis. Finally, the production of recombinant proteins at lower cost and with fewer side effects is used in everyday clinical practice. Gene therapy remains an extraordinary challenge in correcting severe hereditary or acquired diseases. The use of genetically modified animal cell lines producing growth factors, insulin or erythropoetin, which are subsequently encapsulated and transferred to man, represents an attractive approach for gene therapy.
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PMID:[Is molecular biology useful to the practitioner?]. 919 Jun 68

Several important advances have been made in the pathogenesis of mineralocorticoid induced hypertension. A hybrid gene was found to be responsible for glucocorticoid remediable hypertension. This extra gene contains fragments of 11-beta-hydroxylase and aldosterone synthase. The hybrid gene is the result of an unequal crossing-over of the two genes located in close proximity on chromosome 8, and leads to the production of aldosterone and the hybrid steroids 18-hydroxycortisol and 18-oxocortisol. These hybrid steroids are also detected in patients with aldosterone producing adenoma but not in patients with hyperaldosteronism due to bilateral adrenal hyperplasia. In Apparent "Mineralocorticoid Excess", inherited as an autosomal recessive disorder, an increased ratio of urinary cortisol metabolite to cortisone is diagnostic. The syndrome is due to a deficiency of the renal enzyme 11-beta-hydroxysteroid dehydrogenase type II, which protects the mineralocorticoid receptor against cortisol that binds to the mineralocorticoid receptor like aldosterone. Liddle's syndrome is a rare entity and due to a constitute activation of an aldosterone dependent protein which triggers the amiloride sensitive sodium channel in the kidney. This results in hypokalemic hypertension with suppressed aldosterone and renin levels.
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PMID:[Mineralocorticoid-induced hypertension]. 924 33

Blood pressure is a quantitative trait that varies along a continuum in the general population and is regulated via multiple mechanisms involving many genetic loci and environmental factors. Family studies and twin studies suggest that about 30% of blood pressure variance is attributable to genetic factors and 50% to environmental factors. Two forms of hypertension transmitted on an autosomal recessive basis have been identified: one is glucocorticoid-suppressible hyperaldosteronism (GSH) and the other is Liddle's syndrome (amiloride-suppressible hyperactivity of the epithelial sodium channel). The molecular basis for these two forms of severe hypertension has recently been elucidated. GSH is due to expression of a chimeric gene produced by fusion of the 11 beta-hydroxylase promoter with the region encoding the enzyme aldosterone-synthase. Expression of this chimeric gene occurs in the zona fasciculata of the adrenal cortex, under the control of ACTH, and can be suppressed by administration of glucocorticoids. Liddle's syndrome is due to mutations in the beta or gamma chain of the epithelial sodium channel in distal renal tubule cells. The hyperactivity of this channel caused by the mutations results in increased sodium reabsorption, which can be suppressed by administration of amiloride or triamterene. Apart from these rare genetic defects, a number of susceptibility genes can increase the risk of hypertension in a given environment. Their presence is neither necessary nor sufficient to cause hypertension. The best documented example is the angiotensinogen gene. Angiotensiongen is the substrate of renin, and the renin-angiotensinogen reaction is the first and limiting step in the pathway that leads to production of angiotensin II, a peptide with important effects on blood pressure control and the metabolism of water and sodium. Several studies have demonstrated a link between the angiotensinogen gene and familial hypertension or hypertension of pregnancy. The M235T variant of angiotensinogen is more prevalent among hypertensive than among normotensive subjects in several Caucasian and Japanese populations. The M235T variant is also associated with plasma angiotensinogen elevation, which is potentially responsible for increased production of angiotensin II. In other terms, relationships exist between the angiotensinogen genotype, the intermediate phenotype (i.e., plasma angiotensinogen elevation), and the distal phenomenon (i.e., blood pressure elevation). DNA libraries for the study of hypertension have been set up, and many informative genetic markers distributed along the genome have been identified. Using position cloning techniques, these markers could be used in the search for genetic links between arterial hypertension and a chromosomal locus.
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PMID:Molecular genetics of the renin-angiotensin-aldosterone system in human hypertension. 929 68

Genetic defects in aldosterone biosynthesis and action affect blood pressure and electrolyte homeostasis. Aldosterone synthase deficiency, salt-wasting forms of congenital adrenal hyperplasia, and adrenal hypoplasia congenita all cause aldosterone deficiency, signs of which include hyponatremia, hyperkalemia, hypovolemia, elevated plasma renin activity, and sometimes shock and death. Conversely, the inappropriate regulation of aldosterone synthesis seen in glucocorticoid-suppressible hyperaldosteronism may cause hypokalemia, suppressed plasma renin activity, and hypertension. Similar problems occur when the normal ligand specificity of the aldosterone receptor is lost, as in the syndrome of apparent mineralocorticoid excess due to 11 beta-hydroxysteroid dehydrogenase deficiency. The effects of aldosterone are mediated largely through activation of the epithelial sodium channel, and inactivating or activating mutations of this channel leads to signs of mineralocorticoid deficiency or excess, termed pseudohypoaldosteronism and Liddle's syndrome, respectively.
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PMID:Abnormalities of aldosterone synthesis and action in children. 930 Jan 99

Activity of the epithelial sodium channel (ENaC) is a key determinant of sodium homeostasis and blood pressure. Liddle's syndrome, an inherited form of hypertension, is caused by mutations that delete or alter PY domains in the carboxyl termini of beta or gamma ENaC subunits, leading to increased channel activity. In this study we investigated the mechanism of this effect by analysis of wild-type and mutant ENaC activity in Xenopus oocytes. By inhibiting insertion of new channels into the plasma membrane with brefeldin A, we demonstrate that the half-life of the activity of channels containing Liddle's mutations is markedly prolonged compared with wild-type channels (t1/2 of 30 h in mutant versus 3.6 in wild-type, p < 0.001). We investigated the involvement of clathrin-coated pit-mediated endocytosis by co-expressing a dominant-negative dynamin mutant with wild-type ENaC in oocytes. Expression of this specific inhibitor of endocytosis leads to a large increase in the activity of wild-type channels, demonstrating that normal turnover of this channel is through the clathrin-coated pit pathway. In contrast, co-expression of Liddle's mutations and dynamin mutants leads to no further increase in channel activity, consistent with one of the effects of Liddle's mutations being the loss of endocytosis of these channels. These findings demonstrate the normal mechanism of turnover of ENaC from the cell surface and demonstrate a mechanism that can account for the increased number of channels in the plasma membrane seen in Liddle's syndrome.
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PMID:The activity of the epithelial sodium channel is regulated by clathrin-mediated endocytosis. 932 69

A wealth of experimental evidence demonstrates that cerebral ischemia causes excessive release of glutamate and that glutamate contributes to ischemic injury. Glutamate antagonism by any of several mechanisms can ameliorate the extent of infarction. These antagonists comprise noncompetitive blockers of the ion channel associated with the N-methyl-D-aspartate (NMDA) receptor [e.g., aptiganel (Cerestat)], competitive antagonists of the glutamate recognition site of the NMDA receptor (e.g., selfotel) or of the glycine recognition site (e.g., ACEA 1021, GV150526), antagonists at the polyamine site (e.g., eliprodil), and drugs that may interfere with glutamate release by sodium channel blockade as well as having other actions (e.g., lubeluzole, 619C89). Clinical experience suggests that although some NMDA antagonists are poorly tolerated at putative neuroprotective doses (e.g., selfotel), potentially neuroprotective plasma concentrations can be achieved in humans with others (e.g., aptiganel), though tolerable adverse effects are frequently observed. These clinical effects include hypertension (which is probably preferable to the hypotension seen with nimodipine and lifarizine), sedation, confusion or hallucinations and, at high doses, catatonia. Glycine antagonists may be associated with fewer adverse effects, but preclinical studies suggest that brain penetration may be low. Although recent studies with selfotel and eliprodil have been discontinued because of insufficient evidence for a satisfactory risk/benefit ratio, encouraging experience with aptiganel, magnesium, and glycine antagonists has prompted continued clinical trials with these agents. To be of sufficient size to detect a clinically useful improvement in outcome, these trials need to be large (600-1,000 patients). Present trials with aptiganel (Cerestat) are comparing the efficacy and tolerability of two doses vs. placebo in patients treated within 6 hours of ischemic stroke. Outcome is assessed by the modified Rankin Scale at 3 months.
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PMID:Cerestat and other NMDA antagonists in ischemic stroke. 937 Nov 55

BDF 9148, a positive cardiac inotrope, relaxes the rat isolated portal vein and the KCl-contracted rat aorta. The aims of our study were to determine the mechanism of action of BDF 9148, and to ascertain whether the relaxing effect of BDF 9148 was maintained in the presence of the hypertrophy associated with hypertension, by investigating the effects of BDF 9148 on the contractility and electrophysiology of aortae of Wistar Kyoto normo-tensive rats (WKY) and Spontaneously Hypertensive Rats (SHRs). High concentrations of veratridine contracted the quiescent rat aorta. BDF 9148 had no effect on the quiescent, but relaxed the KCl-contracted WKY and SHR aorta by a tetrodotoxin insensitive mechanism, and these relaxations decreased with age but were not greatly altered by hypertrophy. The verapamil relaxations of the KCl-contracted aorta were not altered by age or hypertrophy. The ability of KCl to depolarise the aorta was reversed by verapamil, but not by BDF 9148. On the contracted rat aorta, the relaxant responses to acetylcholine were abolished by removal of the endothelium but potentiated by IBMX (10[-6] M), and the responses to isoprenaline were inhibited by propranolol (10[-6] M) but potentiated by forskolin (10[-7] M). The relaxation responses of the KCl-contracted aorta to BDF 9148 were not altered by removal of the endothelium, or by propranolol, forskolin and IBMX. In summary, the effects of verapamil and BDF 9148 on the aorta are different, and thus it is unlikely that the relaxant responses to BDF 9148 on the aorta are due to calcium channel blocking activity. The mechanism of the relaxant effect of BDF 9148 on the aorta remains unknown, but we have shown the response is endothelium-independent, and not mediated by sodium channel opening, hyperpolarization, beta-adrenoceptors, or by stimulating adenylate cyclase or guanylate cyclase.
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PMID:The relaxing effect of BDF 9148 on the KCl-contracted aorta isolated from normo- and hyper-tensive rats. 952 85


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