Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0004135 (ATM)
 13,001 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Most of the biological effects of the renin-angiotensin system are mediated by the binding of angiotensin II (Ang II) to the type 1 Ang II (AT1) receptor, the predominant receptor subtype present after fetal life. To study tissue-specific regulation of the expression of the AT1 receptor in the rat, we altered activity of the renin-angiotensin system by feeding rats a low (0.07% NaCl), normal (0.3% NaCl), or high (7.5% NaCl) salt chow for 14 days; infusing Ang II (200 ng/kg per minute IP) or vehicle for 7 days; and administering an angiotensin-converting enzyme inhibitor (captopril, 100 mg/dL in the drinking water) or vehicle for 7 days. Renin, angiotensinogen, and total AT1 receptor mRNA levels were measured by slot-blot hybridization with cRNA probes, and AT1 receptor subtypes (A and B) were measured by reverse transcription-polymerase chain reaction in the presence of a cRNA internal standard. Plasma renin concentration and renal renin, renal and hepatic angiotensinogen, and hepatic AT1 receptor mRNA levels were all inversely related to salt intake; in contrast, renal AT1 receptor mRNA levels were significantly lower in rats fed low salt, a difference that was exclusively due to a decrease in the AT1A subtype. This difference did not appear to be mediated by a change in the circulating levels of Ang II, because Ang II infusion reduced plasma renin concentration and renal renin mRNA with no effect on either angiotensinogen or AT1 receptor mRNA levels in kidney or liver, renal Ang II receptor density (determined by in situ autoradiography) decreased, presumably via a posttranscriptional mechanism. Similarly, inhibition of Ang II generation with captopril increased plasma renin concentration and renal renin mRNA levels without altering renal or hepatic angiotensinogen mRNA or renal AT1 receptor mRNA levels. Thus, AT1 receptor gene expression is regulated in a tissue-specific manner that is distinct from other components of systemic and local renin-angiotensin systems and that appears to be mediated by a mechanism other than through changes in the circulating levels of Ang II.
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PMID:Tissue-specific regulation of type 1 angiotensin II receptor mRNA levels in the rat. 879 24

In vitro studies have suggested that vitamin A lowers invasive potential of squamous cell carcinoma. Epidemiological data have also indicated that high dose vitamin A may improve survival in patients with previously resected lung carcinoma. To our knowledge, no studies have attempted to test the in vivo effect of vitamin A on the morphology and growth rate of lung and head and neck cancer. Freshly resected tumor cell suspensions were obtained by ex vivo fine needle aspiration and injected subcutaneously in duplicate in athymic male nude mice. Two to six weeks post-engraftment tests and controls were separated for each xenograft. Mice with test xenografts were given water soluble vitamin A (Aquasol ATM, Astra pharmaceutical, Westborough, MA, U.S.A) at a dose of 10,000 U/Kg/day intraperitoneally for 6 to 10 weeks (median 8 weeks). One to two hours prior to sacrifice bromodexouridine (BrdU) was injected intraperitoneally to assess the S-phase fraction in both test and control xenografts. Blood vitamin A levels in test and control animals were measured after sacrifice using high performance liquid chromatography (HPLC). Sections of test and control xenografts were routinely stained to assess morphologic differentiation and mitotic counts. Unstained sections of xenografts were immunostained by the antibody to BrdU to test for BrdU labeling index (BLI) reflecting S-phase fraction (SPF) and also by the MIB-1 antibody to assess proliferative activity. Eighteen tumors were studied. These included 9 squamous cell carcinomas of the lung, 5 squamous cell carcinomas of the head and neck, and 4 adenocarcinomas of the lung. Blood levels of vitamin A in test animals were 7 to 23 times those of the control animals (median 13 times). Neovascularization of the xenografts was seen in all cases. The morphology and mitotic activity of the test and control xenografts showed no significant difference. SPF and proliferative activity measured by BrdU and MIB-1 immunolabelling respectively showed no significant difference between test and control xenografts. Our study suggests that there is no significant in vivo effect of high dose vitamin A on the morphology and growth rate of xenografted non small cell carcinoma of the lung or squamous cell carcinoma of the head and neck.
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PMID:The effect of high dose vitamin A on the morphology and proliferative activity of xenograft lung and head and neck cancer. 879 35

The angiotensin AT1 receptor antagonists, losartan (2-n-butyl-4-chloro-5-hydroxymethyl-1-[(2'(1H-tetrazol-5-yl)biphen yl-4- yl)methyl]imidazole potassium salt), EXP3174 (2-n-butyl-4-chloro-1-[(2'(1 H-tetrazol-5-yl)biphenyl-4-yl)methyl]imidazole-5-carboxylic acid), GR117289 (1-[[3-bromo-2-[2-(1 H-tetrazol-5-yl)phenyl]-5-benzofuranyl]methyl]-2-butyl-4-chloro-1 H-imidazole-5-carboxylic acid) and LR-B/081 (methyl-2-[[4-butyl-2-methyl-6-oxo-5-[[2'-(1 H-tetrazol-5-yl)[1,1'-biphenyl]-4-yl]methyl]-1(6H)-pyrimidinyl]met hyl]-3- thiophenecarboxylate), given by intraperitoneal (i.p.) injection 15 min before intracerebroventricular administration of angiotensin II, inhibited drinking with the following order of potency: EXP3174 > GR117289 > losartan > LR-B/081. When 20 mumol/kg of each antagonist was i.p. injected 15 min, 4, 12 or 24 h before angiotensin II, EXP3174 and GR117289 inhibited water intake at each observation time, losartan at 4, 12 and 24 h, LR-B/081 only at 4 and 12 h. After per os administration of the same dose 4 or 12 h before angiotensin II, losartan reduced drinking at 4, but not at 12 h; LR-B/081 did not inhibit drinking either at 4 or 12 h. The present results suggest that EXP3174 and GR117289 cross the barrier readily. The effect of i.p. losartan on central angiotensin mechanisms is not prompt, suggesting that it may require conversion to EXP3174. LR-B/081 apparently crosses the barrier less readily than the other antagonists following both i.p. and per os administration.
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PMID:Functional evidence for the ability of angiotensin AT1 receptor antagonists to cross the blood-brain barrier in rats. 883 13

We compared the consequences of chronic angiotensin-converting enzyme (ACE) inhibition with quinapril and of specific AT1 blockade with losartan in a renin-dependent model of hypertension, the (mRen2)27 transgenic rats (TG). Animals were orally treated with 10 mg/kg/24 h of either quinapril (TGQ, n = 13) or losartan (TGL, n = 12) from age 4 to age 9 weeks. Indirect systolic blood pressure (SBP), and sodium and water balances were measured for 3 consecutive weeks. Nine-week-old rats were instrumented to record aortic BP in the conscious state. In addition, they received an infusion of glucose and saline to increase their diuresis and thus allow accurate assessment of their renal excretion during short time periods. These rats were studied for three one-h periods: (a) baseline, (b) after the administration of a bradykinin (BK) antagonist, and (c) after a cross-treatment; i.e., TGQ rats receiving losartan (10 mg/kg intravenously, i.v.) and TGL rats receiving quinapril (10 mg/kg i.v.). TGL rats differed from TGQ rats by an unconsistently lower indirect SBP associated with significantly lower urinary volume and sodium excretion, whereas the sodium balance did not differ between the two groups. In conditions of fixed sodium intake the aortic BP of TGQ rats was still nonsignificantly different from that of TGL rats, and TGQ rats also exhibited two-fold higher natriuresis. The BK antagonist had no effect in either group, whereas losartan decreased the BP of TGQ rats. We conclude that in TG rats ACE inhibition is associated with an increased natriuresis as compared with specific AT1 blockade, an effect that is independent of the sodium intake. Because a BK antagonist had no effect, such a difference might be due to an antinatriuretic effect of AT2 receptors in chronic conditions.
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PMID:Comparison between chronic converting enzyme inhibition and AT1 blockade in mRen2 transgenic rats. 884 62

Properties of systemically applied angiotensin II in stimulating water intake of normally hydrated ducks were studied and the results compared with properties of angiotensin II-responsive neurons of the subfornical organ which are considered as targets for circulating angiotensin II acting as a dipsogen. Following intravenous infusion of hypertonic saline (2000 mosmol.kg-1 at 0.3 ml.min-1 for 1 h), intravenous infusion of 0.3 ml.min-1 isotonic saline with angiotensin II (200 ng.min-1), starting 1 h later, stimulated drinking in each case at an angiotensin II plasma level of about 1400 pg.ml-1. Without hypertonic priming, the same angiotensin II infusion did not stimulate drinking in each experiment; however, if effective, repeated infusions of ANGII induced stable dipsogenic responses. Angiotensin II infusions did not alter plasma levels of antidiuretic hormone. Sar1-Ile8-angiotensin II, a non-selective angiotensin II antagonist, acted weakly as a partial agonist when infused at a dose 200-fold higher than angiotensin II and effectively blocked the dipsogenic action of angiotensin II; this corresponds to the inhibition of angiotensin II-induced excitation by Sar1-Ile8-angiotensin II observed in duck subfornical organ neurons. DuP 753 (losartan), an angiotensin II antagonist specifically blocking AT1 receptors in mammals, had equivocal effects on angiotensin II-induced drinking in ducks at rates 50- and 200-fold higher than angiotensin II, which corresponds to the weak inhibitory action of this compound on angiotensin II-induced neuronal excitation in the duck SFO. Blood pressure was only marginally elevated by the applied angiotensin II dose and Sar1-Ile8-angiotensin II had no effect.
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PMID:Effects of angiotensin II and its blockers Sar1-Ile8-angiotensin II and DuP 753 on drinking in ducks in relation to properties of subfornical organ neurons. 888 7

Several studies are reviewed in which behavioral aspects of angiotensin (Ang) II on fluid intake have been compared with induction of the immediate early gene product, Fos, as a marker of neuronal activation in rat bain. Either peripheral or central administration of Ang II induced Fos along the lamina terminalis (SFO, MnPO, AV3V) and in the magnocellular neurosecretory groups (SO, PVH). A similar pattern is seen with central injection of renin. Both pharmacological and antisense oligonucleotide probe studies indicate that an AT1 receptor is involved, probably with the initial transduction in the SFO. Treatments that induce sodium appetite all induce Fos along the lamina terminalis, but usually not in the SO or PVN. Kininase II inhibitors, such as captopril, acutely potentiate drinking to Ang I, but after chronic exposure they may inhibit water intake. In contrast, the dipsogenic effect of bradykinin which is manifest in the presence of acute captopril remains unaffected by chronic administration. This suggests that the sodium appetite that appears with chronic captopril treatment may depend in part on peptides other than Ang.
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PMID:Angiotensin-related induction of immediate early genes in rat brain. 889 88

The physiological role of brain Ang II and acetylcholine in mediating water deprivation-induced drinking was assessed in male Sprague-Dawley rats. Specific receptor antagonists were intracerebroventricularly (i.c.v.) administered in 48-h water-deprived rats. When water was given 20 min after i.c.v. injection, PD 123319 almost totally blocked the drinking response. However, losartan and CGP 42112A produced an approx. 20% inhibition of water intake. Central blockade of AT1 receptor with KR 31080 and cholinergic receptor with atropine attenuated water intake more than 50% which was significantly greater than inhibition produced by losartan and CGP 42112A. Atropine given alone or mixed with losartan and CGP-42112A produced a similar magnitude of inhibition of water intake. When water was given 90 min after i.c.v. injection, losartan or CGP-42112A produced a significantly greater inhibition of water intake than when water was given 20 min after injection. The present results suggest that both the central angiotensinergic and cholinergic system play an important role in the physiological drinking response after water deprivation. Both brain AT1 and AT2 receptors are involved in dehydration-induced drinking, but relative contribution of the receptors remains to be clarified.
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PMID:Effect of brain angiotensin II AT1, AT2, and cholinergic receptor antagonism on drinking in water-deprived rats. 889 91

Intracerebroventricular 100,000 pmol losartan (an AT1-receptor blocker) inhibited the initial drinking response of Wistar rats to 1 ml 2 M NaCl given subcutaneously but the intake over 3 h was not significantly inhibited. The same dose of the AT2-receptor blocker PD123319 had a more long-lasting inhibitory effect. Rats of three different strain, Wistar, Wistar-Kyoto (WK), and SH (spontaneously hypertensive), were subjected to sodium depletion using frusemide and a low-sodium diet; in the 3 h after 1.8% NaCl was made available, the intakes were 11.6 +/- 1.7 (SEM), 4.1 +/- 1.2 and 12.4 +/- 1.3 ml, respectively; water intakes in the same period averaged 4.2 +/- 1.1, 5.0 +/- 1.1 and 8.3 +/- 1.8 ml. The intake of both fluids by Wistar rats was not significantly affected by either losartan or PD123319. The intake of both saline and water in SHR rats was reduced by losartan. In evaluating the effect of antagonists to angiotensin II on the intake of water and NaCl in response to perturbations of hydromineral balance, difference in the route of administration of the stimulus and strain of the animals used must therefore be taken into account.
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PMID:The effect of losartan on drinking and NaCl intake in the rat in response to hyperosmotic and hypovolaemic stimuli: effect of route of administration and strain of rat. 889

The concentration of angiotensin II reported in proximal tubular fluid in anaesthetized rats is considerably higher than in plasma, indicating secretion of this peptide into the tubular lumen. Shrinking split-drop micropuncture was used to examine the effect of endogenous angiotensin on sodium and water absorption in the proximal convoluted tubule. Addition of losartan, a nonpeptide AT1 receptor blocker, to intratubular fluid increased fluid uptake by 15.7 +/- 3.9% (10(-5) M) and 24.7 +/- 9.4% (10(-4) M) whereas the AT2 inhibitor, PD123319 had no effect. We conclude that angiotensin II is secreted into proximal tubular fluid and, in the anaesthetized rat, is maintained at a concentration that inhibits sodium and water transport via AT1 receptors.
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PMID:Modulation by locally produced luminal angiotensin II of proximal tubular sodium reabsorption via an AT1 receptor. 890 32

The effects of chronic treatment with the specific AT1 angiotensin receptor antagonist, irbesartan, or the angiotensin converting enzyme inhibitor, enalapril, were assessed in uninephrectomized fawn-hooded hypertensive rats (FHH) and compared with vehicle treatment. Three days after uninephrectomy, irbesartan (240 mg/liter), enalapril (80 mg/liter) or vehicle were administered via the drinking water. Systolic blood pressure (SBP) and protein excretion rates (UprotV) were determined monthly. In rats receiving irbesartan (N = 7) and enalapril (N = 6) SBP (132 +/- 3 mm Hg and 133 +/- 6, respectively) was essentially normalized at 12 weeks when compared with vehicle (169 +/- 6 mm Hg (N = 6); all comparisons were P < 0.05 by ANOVA). Similarly, proteinuria was lower in irbesartan (44 +/- 12 mg/day) and enalapril (19 +/- 2) groups versus vehicle (123 +/- 10 mg/day). Treatment with both drugs was associated with marked reduction in glomerulosclerosis at 12 weeks (both < 5% vs. vehicle, 43 +/- 9%) without effect on glomerular volume. In identically prepared rats, glomerular capillary hydraulic pressure (PGC, estimated from stop-flow pressure, Psf) was lower in FHH receiving irbesartan (58 +/- 1 mm Hg, N = 6) or enalapril (54 +/- 2, N = 6) than in vehicle-treated rats, in whom PGC was greatly elevated (68 +/- 2 mm Hg; N = 7). Despite this, GFR and single nephron GFR were well maintained. These data support a critical role for AT1 receptor-mediated, angiotensin-dependent processes in the pathogenesis of hypertension in FHH, and further implicate elevated PGC as a major determinant of glomerular injury in this model.
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PMID:The angiotensin receptor antagonist, irbesartan, reduces renal injury in experimental chronic renal failure. 894 34


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