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)

Keeping in mind the vasodilator action of prostaglandins, the control that they exercise over the vascular supply of kidneys and the sympathetic activity, research was conducted in order to establish the effect of arachidonic acid, the precursor of PGE2, on experimental hypertension in the rat. The experimental hypertension was induced by unilateral nephrectomy, followed by the administration of DOCA and the elevated sodium diet. The treatment was short in one group, long in the other, and both groups were compared to a control hypertensive group which received no treatment at all. Arachidonic acid worsened the experimental hypertension by 37% in the long treatment, and by 25% in the short treatment. The administration of lysine-acetylsalicylate diminished this hypertension. A non-saturated acid, oleic acid, which is not involved in prostaglandin synthesis, has no action. The authors would like to emphasize that in one of the previous experiments, L-tyrosine, the precursor of catecholamines, diminished the experimental hypertension in the rat, and also that L-DOPA and IMAO (MAOI) have comparable effects. It seems, therefore, that the depression of the central catecholaminergic activity, which is supposed to be the action of arachidonic acid via an increase in the PGE2 synthesis, appears to increase hypertension. It is noteworthy that the medial forebrain bundle (MFB) is catecholaminergic and that the periventricular system (PVS) is cholinergic. Thus hypertension may represent the peripheral vascular response to anguish which results from the activation of PVS and from the depression of MFB.
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PMID:The action of arachidonic acid on experimental hypertension in the rat. 112 60

Tyrosine exerts potent cardiovascular effects: smaller doses induce tachycardia and hypertension while higher doses induce bradycardia and hypotension. However, the direct cardiac effects of this amino acid have not been characterised. In the present study increasing doses of L-tyrosine were administered to the perfusate of isolated rat (0.01-10.0 mg) and rabbit (0.5-40.0 mg) hearts. Heart rate and isometric force of contraction or amplitude of contractions, and either perfusion pressure or flow of perfusate were recorded. In rat hearts L-tyrosine decreased heart rate and isometric force of contraction. In rabbit hearts L-tyrosine also decreased heart rate and amplitude of contractions. The effects on coronary vasculature were variable. In rat hearts, high doses of L-tyrosine induced bi-phasic changes with initial coronary dilatation, followed by vasoconstriction. In rabbit hearts the predominant effect of L-tyrosine was coronary artery constriction. These results show that the inhibitory cardiovascular effects of L-tyrosine in vivo may be at least in part, explained by direct cardiac effects of this amino acid.
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PMID:Depressant effects of L-tyrosine on isolated perfused rat and rabbit hearts. 233 75

Tyrosine is the precursor of catecholamines. Small doses of tyrosine produce tachycardia and hypertension while higher doses produce bradycardia and hypotension in anaesthetised rats. The mechanism of these effects has not been established. An increased synthesis and release of catecholamines has been suggested to be the mechanism. Various pretreatments were given to anaesthetised Wistar rats to study the influence of a blockade of L-tyrosine metabolism and thus a blockade of catecholamine synthesis, on these cardiovascular effects: valine, which inhibits tyrosine uptake into brain, alpha-methyl-p-tyrosine, which blocks the rate-limiting enzyme, tyrosine hydroxylase, carbidopa and benserazide, which both inhibit dopa decarboxylase, and desipramine, which blocks catecholamine re-uptake. Benserazide and alpha-methyl-p-tyrosine partially blocked the stimulatory effects of tyrosine. None of the pretreatments were able to block effectively the inhibitory effects of L-tyrosine. Therefore, the metabolism of tyrosine to form catecholamines may be involved in the stimulatory but not in the inhibitory cardiovascular effects of L-tyrosine. Valine pretreatment did not antagonize the depressant effects of tyrosine. Since valine blocks the uptake of L-tyrosine into the brain, the depressant effects of L-tyrosine might be peripheral rather than central in origin.
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PMID:Cardiovascular effects of L-tyrosine: influence of blockade of tyrosine metabolism. 256 1

Tyrosine is the precursor amino acid of catecholamines. Low doses of tyrosine produce tachycardia and hypertension, while higher doses induce bradycardia and hypotension in anaesthetised rats. The mechanism and site of action of L-tyrosine are not fully understood. Eight groups of Wistar rats received different pretreatments in order to study the influence of blockade of various receptor mechanisms on the cardiovascular effects of L-tyrosine. The effects mediated by the autonomic nervous system were inhibited by ganglion blockade (hexamethonium), by alpha 1- and beta 1-adrenoceptor blockade (prazosin and atenolol) and by parasympathetic acetylcholine receptor blockade (atropine). The possible role of histamine receptors was studied by inducing H1 and H2-receptor blockade (diphenhydramine and cimetidine, respectively). The effect of inhibition of prostaglandin synthesis by indomethacin was also studied. The L-tyrosine-induced tachycardia was completely blocked by atenolol. Both atenolol and prazosin partly inhibited the hypertensive effects of low doses of tyrosine. The tyrosine-induced bradycardia was not inhibited, and the hypotension was only partly blocked by the pretreatments. Therefore, adrenergic mechanisms seem to mediate the stimulatory cardiovascular effects of tyrosine. The depressant effects of high doses of tyrosine do not appear to be mediated by cholinergic activation, histamine receptor activation, or prostaglandin synthesis.
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PMID:Further studies on the mechanism of the cardiovascular effects of L-tyrosine. 257 35

The antihypertensive effect of chronic administration of L-tyrosine (Tyr) was investigated in a two-part study. In the first experiment, adult male Sprague-Dawley rats were assigned to 1 of 4 treatment groups: control diet plus unilateral nephrectomy (Nphx) and 0.15 M NaCl (Sal) as the sole drinking solution (C-CTRL); control diet plus deoxycorticosterone acetate (DOCA, 268 micrograms/rat/day), Nphx, and Sal (C-DOCA); control diet supplemented with 2.5% L-p-Tyr plus Nphx and Sal (Tyr-CTRL), and Tyr plus DOCA, Nphx, and Sal (Tyr-DOCA). Systolic blood pressure (SBP) increased within 2 weeks after initiation of treatment with DOCA-salt and remained elevated throughout the duration (8 weeks) of the study (p less than 0.001). Dietary administration of Tyr to DOCA-treated rats failed either to affect SBP in normotensive rats or the elevation of SBP in DOCA-treated rats. Dietary supplementation with Tyr induced a significant elevation in urinary excretion of free dopamine (week 1, 3, 5, and 7) and a decreased excretion of free norepinephrine (week 1) without regard to DOCA treatment. Metabolic responsiveness (change in colonic temperature) and cardiovascular responsiveness (change in heart rate) to subcutaneous administration of the beta-adrenergic agonist, isoproterenol, were significantly prolonged while alpha 2-adrenoceptor number (cerebral cortical membranes; 3H-yohimbine binding) was reduced in rats receiving Tyr. In the second experiment, similar rats were assigned to 1 of 3 treatment groups: control diet plus Nphx and Sal, control diet plus Nphx, DOCA and Sal, and Tyr plus DOCA, Nphx, and Sal; however, Tyr was not started until DOCA-salt-induced hypertension developed (4 weeks). Neither acute (2.5 h post-meal) nor chronic (4 weeks) effects of administration of Tyr on SBP were noted. Thus, the Tyr-induced changes observed in these studies include a chronic increase in free dopamine, and a transient decrease in norepinephrine, excretion. No significant effects of Tyr on blood pressure of DOCA-salt-treated rats were observed.
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PMID:Physiologic responses to chronic dietary tyrosine supplementation in DOCA-salt-treated rats. 303

The blood pressure of spontaneously hypertensive rats (SHR) was measured by tail-plethysmography. Feeding SHR a diet supplemented with 0.6 g% L-tyrosine, for 15 weeks after weaning, resulted in a slower increase of blood pressure than in rats fed the control diet (no tyrosine added). The blood pressure stabilized, after about 8 weeks, at values lower by about 10 mm Hg than in the control SHR group. Diets with a higher content of free L-tyrosine (1.2 or 2.4 g%) produced no greater hypotensive effects, despite the fact that the plasma level of the amino acid, at the time of blood pressure measurements, was related to the tyrosine content of the diet. In addition, providing 2.4 g% free L-tyrosine to the diet of SHR with established hypertension, produced within a few days a decrease of blood pressure similar to the one recorded in rats fed the tyrosine-supplemented diet during the whole period of development of hypertension. A maximal effect of L-tyrosine, in decreasing the blood pressure of SHR, is thus obtained at relatively low concentrations of the amino acid in the diet, and after a short period of consumption. However, this effect is rather small, and rapidly reversed upon removing free L-tyrosine from the diet.
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PMID:Development of hypertension in spontaneously hypertensive rats fed L-tyrosine-supplemented diets. 684 71

Dual inhibitors of the two zinc metallopeptidases, neutral endopeptidase (NEP, EC 3.4.24.11) and angiotensin-I-converting enzyme (ACE, EC 2.4.15.1), have been the focus of much clinical interest for the treatment of hypertension and congestive heart failure. We have previously reported that compound 2 (N-[[1-[(2(S)-mercapto-3-methyl-1-oxobutyl) amino]-1-cyclopentyl]-carbonyl]-L-tyrosine) was a potent dual inhibitor in vitro (IC50 (ACE) = 7.0 nM, IC50 (NEP) = 1.5 nM) (Fink et al. J. Med. Chem. 1995, 38, 5023-5030). This compound was found to have oral activity; however, its duration of effect was short. A series of thioacetate carboxylic acid ester analogs of compound 2 was prepared. Modifications were also made to the tyrosine phenol. These compounds were evaluated for their ability to inhibit plasma ACE activity when administered orally to conscious normotensive rats. Most of the compounds prepared were found to be orally active with longer durations of effect than compound 2. Compound 38 (N-[[1-[(2(S)-(acetylthio)-3-methyl-1-oxobutyl) amino]-1-cyclopentyl]carbonyl]-O-methyl-L-tyrosine ethyl ester), administered at 11.7 mg/kg po, was found to be more efficacious than captopril at 10 mg/kg po. This compound was also found to inhibit plasma NEP activity following oral administration to conscious rats and was more efficacious than acetorphan. Compound 38 was found to lower blood pressure in the aorta-ligated rat and the spontaneously hypertensive rat when administered orally. The synthesis and biological activity of these dual inhibitors are discussed.
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PMID:Mercaptoacyl dipeptides as orally active dual inhibitors of angiotensin-converting enzyme and neutral endopeptidase. 875 37

a-Methyldopa sesquihydrate is used in the treatment of hypertension; over 20 million prescriptions are written annually for a -methyldopa or a-methyldopa sesquihydrate in the United States. a-Methyldopa sesquihydrate (USP grade, greater than 99% pure) was selected for study because of widespread human exposure and the lack of carcinogenicity studies on this compound. Fourteen-day, 13-week, and 2-year studies were conducted in F344/N rats and B6C3F1 mice. The chemical was administered in feed because human exposure is primarily by the oral route. Short-term studies were performed in bacteria and mammalian cells to evaluate the potential for genetic damage. Fourteen-Day and Thirteen-Week Studies: In the 14-day studies, the chemical was administered at dietary concentrations of 0 and 6,250-100,000 ppm. All rats receiving 100,000 ppm and 2/5 female rats receiving 50,000 ppm died. All mice lived until the end of the studies. Final mean body weights of dosed male rats were 14%-43% lower than that of controls, and those of dosed female rats were 9%-24% lower. Feed consumption by dosed male and female rats was reduced. Final mean body weights of dosed mice were generally within 10% of those of controls; feed consumption by dosed groups was lower than that by controls during the first week of the studies. In the 13-week studies, the chemical was administered at dietary concentrations of 0 and 3,100-50,000 ppm. Deaths occurred in 4/10 male rats, 7/10 female rats, and 2/10 female mice at 50,000 ppm and in 1/10 female rats at 25,000 ppm. Final mean body weights of dosed rats were 6%-46% lower than those of controls. Feed consumption by dosed rat groups was lower than that by controls. Final mean body weights of male mice at 25,000 and 50,000 ppm and female mice at 50,000 ppm were reduced 12%-19%. Feed consumption by dosed and control mice was comparable. Rats and mice receiving 25,000 and 50,000 ppm exhibited clinical signs of toxicity including lethargy, hyperexcitability, ocular discharge, and rough hair coats. Clinical signs of toxicity were judged to be more severe in dosed male mice than in female mice. Minimal to moderate kidney tubular cell regeneration was seen in male and female rats at 12,500, 25,000, and 50,000 ppm. Bone marrow hypoplasia occurred in male rats at 25,000 and 50,000 ppm and in female rats at 6,300 ppm and higher. Nuclear enlargement (karyomegaly) of the renal corticaltubular epithelium was observed in male and female mice administered 12,500-50,000 ppm; these kidney lesions were judged to be more severe and occurred more frequently at concentrations of 25,000 ppm and higher. Because of kidney lesions, bone marrow responses, and body weight effects at 12,500 ppm and higher and increased deaths and clinical signs at 25,000 and 50,000 ppm, dietary concentrations selected for male and female rats in the 2-year studies were 0, 3,100, and 6,300 ppm. Based on clinical signs, kidney effects, and body weight decreases at 25,000 and 50,000 ppm, dietary concentrations selected for male and female mice in the 2-year studies were 0, 6,300, and 12,500 ppm. Diets containing the chemical at these concentrations were fed to groups of 50 male and 50 female rats and 50 male and 50 female mice for 103 weeks. Body Weight and Survival in the Two-Year Studies: Mean body weights of dosed rats were generally 8%-17% lower than those of controls, and mean body weights of dosed mice were generally 5%-22% lower than those of controls throughout the studies. The average amount of a-methyldopa sesquihydrate consumed per day was approximately 110-120 or 230-240 mg/kg per day by low and high dose rats and 830-890 or 1,760-1,800 mg/kg by low and high dose mice. Survival was comparable among dosed and control groups (male rats: control, 28/50; low dose, 26/50; high dose, 27/50; female rats: 35/50; 34/50; 29/50; male mice: 44/50; 42/50; 39/50; female mice: 42/50; 40/50; 38/50). Clinical signs considered to be dose-related included fighting in male rats, irritability in male mice, and rough hair coats in female mice. Nonneoplastic and Neoplasle rats, irritability in male mice, and rough hair coats in female mice. Nonneoplastic and Neoplastic Effects in the Two-Year Studies: Several lesions of the forestomach, including edema, chronic inflammation, epithelial hyperplasia, and ulcers, were seen at low incidences in high dose rats. No forestomach neoplasms occurred. No neoplastic lesions were observed in either male or female rats which were considered related to a-methyldopa sesquihydrate exposure. Nephropathy (control, 3/50; low dose, 21/50; high dose, 32/50), karyomegaly (nuclear enlargement) of cells of the tubular epithelium (0/50; 46/50; 44/50, and cysts (2/50; 10/50; 10/50) were observed in the kidney of dosed female mice. Low incidences of tubular cell hyperplasia (0/50; 1/50; 1/50), tubular cell adenomas (0/50; 2/50; 0/50), and tubular cell adenocarcinomas (0/50; 0/50; 1/50) were observed in male mice. Tubular cell adenomas (3/2,029, 0.15%) and tubular cell adenocarcinomas (3/2,029, 0.15%)are uncommon in untreated control male B6C3F1 mice. No neoplastic lesions in female mice were considered related to a-methyldopa sesquihydrate exposure. Decreased incidences of several site-specific neoplasms were observed in dosed rats and mice; these decreases might have been due in part to decreased weight gain in dosed groups. The decreases occurred in the adrenal medulla of male rats (pheochromocytomas or malignant pheochromocytomas, combined: 21/49; 3/49; 10/50), uterus of female rats (endometrial stromal polyps: 15/50; 5/49; 1/50), liver of male and female mice (hepatocellular adenomas or carcinomas, combined-- male: 15/50; 5/50; 6/50; female: 4/50; 1/50; 0/50), and anterior pituitary gland of female mice (adenoma: 9/49; 4/40; 2/50). The incidences of malignant tumors (male: 19/50; 9/50; 8/50; female: 21/50; 16/50; 12/50) and benign or malignant tumors (combined) (male: 32/50; 15/50; 17/50; female: 33/50; 22/50; 21/50) were reduced in dosed mice. Reproductive Studies: a-Methyldopa sesquihydrate was administered to male F344/N rats in corn oil by gavage 5 days per week for 65 days at doses of 0, 50, 100, 200, or 400 mg/kg. Decreased body weight was seen in dosed animals. Male rats were mated to untreated female F344/N rats on days 57-61, necropsies were performed on days 65-67, and reproductive toxicity was measured by sperm count, sperm motility, organ weights, hormone levels, and histologic evaluation of the testis. Decreased fertility was observed in males dosed with a-methyldopa sesquihydrate at 200 and 400 mg/kg. Decreases were also seen in sperm count, sperm motility, apparent number of late spermatids, and plasma testosterone levels in males in the 200 and 400 mg/kg groups. This alteration of reproductive function in male rats was found to be reversible after a 13-week recovery period (without dosing). The decreased fertility observed after a-methyldopa sesquihydrate administration was probably due in part to the decreases in plasma testosterone levels. Genetic Toxicity: a-Methyldopa sesquihydrate was not mutagenic when tested with or without exogenous metabolic activation with a preincubation protocol in four strains of Salmonella typhimurium (TA97, TA98, TA100, or TA1535). No increase in chromosomal aberrations or sister chromatid exchanges was observed in Chinese hamsterovary (CHO) cells exposed to a-methyldopa sesquihydrate with or without S9. Audit: The data, documents, and pathology materials from the 2-year studies of a-methyldopa sesquihydrate have been audited. The audit findings show that the conduct of the studies is documented adequately and support the data and results given in this Technical Report. Conclusions: Under the conditions of these 2-year feed studies, there was no evidence of carcinogenic activity of a-methyldopa sesquihydrate for male or female F344/N rats fed diets containing 3,100 or 6,300 ppm. There was equivocal evidence of carcinogenic activity of a-methyldopa sesquihydrate for male B6C3F1 mice, as shown by three dosed mice having uncommon tubular cell tumors of the kidney. There was no evidence of carcinogenic activity of a -methyldopa sesquihydrate for female B6C3F1 mice fed diets containing 6,300 or 12,500 ppm. Nonneoplastic lesions of the kidney including karyomegaly were observed in dosed female mice. Decreased incidences of several tumor types (in the adrenal gland in male rats, uterus in female rats, liver in male and female mice, and anterior pituitary gland in female mice) were considered related to a-methyldopa sesquihydrate exposure. Synonyms for a-Methyldopa or a-Methyldopa sesquihydrate: 3-hydroxy-a-methyl-L-tyrosine sesquihydrate; L-(a-MD); a-methyl-L-3,4-dihydroxyphenylalanine; L(-)-b-(3,4-dihydroxyphenyl)-a -methylalanine; L-(-)-3-(3,4-dihydroxyphenyl)-2-methylalanine; L-a-methyl-3,4-dihydroxyphenylalanine; a-methyl-b-(3,4-dihydroxyphenyl)-L-alanine; L-(-)-a-methyl-b-(3,4-dihydroxyphenyl)alanine; (-)-methyldopa; L-methyldopa; L-a-methyldopa; a-methyl-L-dopa Trade Names for a-Methyldopa or a-Methyldopa sesquihydrate: Aldomet; Aldometil; Aldomin; a-Medopa; AMD; Bayer 1440 L; Baypresol; Dopamet; Dopatec; Dopegyt; Hyperpax; Medomet; Medopren; Methoplain; MK. B51; MK-351; Presinol; Presolisin; Sedometil; Sembrina
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PMID:NTP Toxicology and Carcinogenesis Studies of alpha-Methyldopa Sesquihydrate (CAS No. 41372-08-1) in F344/N Rats and B6C3F1 Mice (Feed Studies). 1270 36

TH01 is a tetrameric short tandem repeat locus located in intron 01 of the tyrosine hydroxylase gene. The tyrosine hydroxylase catalyzes the hydroxylation of L-tyrosine to L-DOPA and is the rate limiting enzyme in the synthesis of catecholamines like noradrenaline or adrenaline, which are pivotal in the regulation of blood pressure. In a clinical study a strong correlation between alleles *9.3 and *10 and essential hypertension was observed ([2] Hypertension 32: 676-682). To further investigate this association, we typed TH01 in 296 autopsy cases and correlated the genotypes to the heart weight as parameter for myocardial hypertrophy. No significant correlation was observed. Moreover, dividing the studied cases into 2 groups, one including 172 casualties from hypertension-associated diseases (myocardial infarction, left heart failure, aortic aneurysm, spontaneous intracerebral bleeding and cerebral infarction) and one consisting of 124 cases of death unrelated to hypertension, revealed similar allelic frequencies for both groups. Our data thus suggest that TH01 long alleles appear not to lead to a significant increase in the incidence of myocardial hypertrophy or other hypertension associated diseases. This could be explained by a relatively small impact of the TH01 genotype on the blood pressure or by counteraction of another mechanism related to catecholamines and their effect on the human body.
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PMID:TH01, a tetrameric short tandem repeat locus in the tyrosine hydroxylase gene: association with myocardial hypertrophy and death from myocardial infarction? 1573 19