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Query: UMLS:C0011570 (depression)
 172,036 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effects of torasemide (0.1 and 1 mg kg-1, i.v.) and furosemide (3 mg kg-1) on renal haemodynamics and excretory responses in the presence of angiotensin II and endothelin-1 was examined in anaesthetized dogs. Angiotensin II or endothelin-1 was continuously infused into the renal artery throughout the experiment and a bolus of torasemide or furosemide was injected into the bracheal vein. Continuous intrarenal arterial (i.r.a.) infusion of angiotensin II, at a dose of 5 ng kg-1 min-1, increased renal vascular resistance (RVR) and decreased renal blood flow (RBF) and glomerular filtration rate (GFR), but had no effect on systemic mean arterial pressure (MAP). Urinary excretion of sodium (UNaV) and urine flow (UF) were significantly decreased during angiotensin II infusion. Intravenous injections of torasemide in the presence of angiotensin II caused a dose-dependent increase in UF, UNaV and urinary excretion of potassium (UKV), while a decrease in RVR was accompanied by an increase in RBF. UKV was greater in the furosemide group than in the torasemide group, despite both groups having the same degree of aquaresis and natriuresis. Continuous i.r.a. infusion of endothelin-1, 1.5 ng kg-1 min-1, produced effects similar to those of angiotensin II on renal haemodynamics; however, the onset of action was extremely slow compared with the effects produced by angiotensin II. Endothelin-1 caused a significant decrease in UF, UNaV and UKV only at a later period, despite a relatively early depression of renal haemodynamics. Torasemide and furosemide also produced a sufficient diuretic action in this model.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Diuretic action of the novel loop diuretic torasemide in the presence of angiotensin II or endothelin-1 in anaesthetized dogs. 135 Jun 26

Angiotensin II inhibits nonadrenergic (purinergic) neurotransmission in the vas deferens and potentiates adrenergic neurotransmission and prostaglandin (PG)E synthesis. Other angiotensin responses are sensitive to either dithiothreitol or pertussis toxin. The present study tested the hypothesis that dithiothreitol or pertussis toxin selectively depress angiotensin responses in the vas deferens. The dithiothreitol (10 mM) eliminated the potentiation of both adrenergic neurotransmission and PGE synthesis but did not alter the depression of purinergic neurotransmission. In contrast, pertussis toxin (100 ng/ml for 3 hr) eliminated the depression of purinergic neurotransmission but had no effect on adrenergic neurotransmission or PGE synthetic responses to angiotensin II. The results are consistent with the existence of at least two transduction pathways for angiotensin II, one enhancing adrenergic neurotransmission and PGE synthesis and the other depressing purinergic neurotransmission. The results indicate that the vas deferens is a useful preparation in defining selective actions of angiotensin receptor agonists or antagonists.
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PMID:Pharmacological differentiation of angiotensin effects in the rabbit isolated vas deferens with dithiothreitol and pertussis toxin. 215 55

We examined the effect of two angiotensin receptor antagonists on neuromodulatory and prostaglandin-producing effects of angiotensin II in the rabbit isolated vas deferens because prior studies have established that angiotensins selectively influence the two neural events, one being adrenergic and the other nonadrenergic. Angiotensin II increased adrenergic neurotransmission and prostaglandin E synthesis in a concentration-dependent manner while depressing nonadrenergic neurotransmission. The [1-Sarcosine, 8-Alanine]-angiotensin II preferentially antagonized adrenergic neuromodulatory effects of angiotensin II. In contrast, the nonadrenergic neuromodulatory and prostaglandin E-releasing effects of angiotensin II were suppressed by [1-Sarcosine, 8-Alanine]-angiotensin II to a lesser extent. The nonpeptide angiotensin receptor antagonist, Dupont 753 (2-n-butyl-4-chloro-5-hydroxymethyl-1-[2(1)-(1-H-tetrazol-5-yl) biphenyl-4-yl)methyl] imidazole, potassium salt, exhibited the opposite selectivity. It eliminated the depression of nonadrenergic neurotransmission without significantly altering the potentiation of adrenergic neurotransmission caused by angiotensin II. The angiotensin-induced stimulation of prostaglandin E synthesis was also eliminated by this antagonist. These data suggest that angiotensin effects in the vas deferens are mediated by at least two types of angiotensin receptors.
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PMID:Selective blockade of angiotensin responses in the rabbit isolated vas deferens by angiotensin receptor antagonists. 226 11

Angiotensin II (ANG II) infusion has been reported to impair barrier size selectivity and exacerbate proteinuria in the rat. To examine whether this is also true of humans, we infused a pressor dose of ANG II into seven healthy controls and seven nephrotic patients. A prompt depression of glomerular filtration rate (GFR) and renal plasma flow was observed in each group (P less than 0.01). Surprisingly, the excretion rates of albumin (5.3 +/- 1.6 to 2.8 +/- 0.3 in controls and 4,791 +/- 1,244 to 3,833 +/- 800 micrograms/min in nephrotics) and immunoglobulin G (1.5 +/- 0.4 to 0.8 +/- 0.2 and 305 +/- 87 to 255 +/- 94 micrograms/min, respectively) fell significantly during ANG II infusion. Fractional clearances of dextrans of broad size distribution (radii 34-54 A) were uniformly elevated by ANG II infusion in controls but tended to decline in nephrotics. A heteroporous model of the glomerular capillary wall revealed ANG II to have a negligible effect on membrane-pore structure. However, the depressed GFR lowered the rate at which macromolecule-rich filtrate was formed through a subset of nondiscriminatory pores from 272 to 176 microliters/min in controls and from 394 to 334 microliters/min in nephrotics. We conclude that, in striking contrast to the rat, pressor ANG II infusion has little or no influence on barrier size selectivity in humans but exerts an antiproteinuric effect by lowering the filtered protein load.
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PMID:Effect of angiotensin II infusion on the human glomerular filtration barrier. 247 34

Angiotensin II stimulates sequential phospholipase C-mediated hydrolysis of initially the polyphosphoinositides and subsequently phosphatidylinositol (PI) in cultured rat aortic smooth muscle cells resulting in biphasic, sustained formation of diacylglycerol (DG). The mechanisms underlying this delayed induction of sustained DG accumulation are unknown but may be related to cellular events including processing of the angiotensin II receptor-ligand complex. In the present study, we characterized the kinetics of angiotensin II receptor sequestration and studied the effects of interventions which interfere with receptor processing on the pattern of angiotensin II-induced DG formation and phosphoinositide hydrolysis. Conversion of the angiotensin II receptor to an acid-resistant form was temperature-dependent, with half-times of 1.5 min at 37 degrees C and 7 min at 19 degrees C. Reducing the temperature to 25 or 19 degrees C caused a marked temporal separation between the two phases of DG accumulation. There was a close temporal correlation between the effect of temperature on receptor sequestration and on sustained DG accumulation. Furthermore, phenylarsine oxide (5 min, 10 microM), which inhibited angiotensin II receptor internalization, also selectively inhibited the sustained phase of DG accumulation (81 +/- 6% inhibition). Monensin and chloroquine, which interfere with receptor processing through the lysosomal-degradative pathway, had no effect on angiotensin II-induced DG formation in these cells, suggesting that the processing event important to hormonally induced sustained DG accumulation occurs early in the internalization pathway, probably at the level of the plasma membrane. Moreover, the acid-resistant state of the angiotensin II receptor-ligand complex retained its ability to signal, since removal of the surface signal by competitive antagonism with Sar1-Ile8-angiotensin II or acid-wash only slowly reversed accumulation of DG and depression of total cell calcium. These experiments support our previous observation that the initial and sustained phases of angiotensin II-induced diacylglycerol formation in vascular smooth muscle are differentially controlled and suggest that an early event in the cellular processing of the angiotensin II-receptor complex is essential to maintenance of DG accumulation.
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PMID:Correlation of receptor sequestration with sustained diacylglycerol accumulation in angiotensin II-stimulated cultured vascular smooth muscle cells. 282 94

Angiotensin II (ANG II) is one of the body's most powerful regulators of Na excretion, operating through extrarenal mechanisms, such as stimulation of aldosterone secretion, as well as intrarenal mechanisms. Considerable evidence suggests that the intrarenal actions of ANG II are quantitatively more important than changes in aldosterone secretion in the normal day-to-day regulation of Na balance and arterial pressure. ANG II at physiological concentrations increases proximal tubular reabsorption, but further studies are needed to determine whether ANG II also has an important effect on more distal tubular segments. ANG II also markedly constricts efferent arterioles, tending to increase Na reabsorption by altering peritubular capillary physical forces and also helping to prevent excessive decreases in glomerular filtration rate. ANG II may also decrease Na excretion and increase urine concentrating ability by reducing renal medullary blood flow. Regulation of Na excretion by ANG II is closely linked with arterial pressure control and volume homeostasis through the renal pressure natriuresis mechanism. Under many physiological conditions, such as changes in Na intake, ANG II greatly multiplies the effectiveness of the pressure natriuresis mechanism to prevent fluctuations in body fluid volume and arterial pressure. In circumstances associated with circulatory depression, such as decreased cardiac function, reductions in blood pressure and increased ANG II formation cause Na retention until arterial pressure is restored to normal. However, in pathophysiological conditions in which ANG II is inappropriately elevated, increased arterial pressure (hypertension) is required for the kidney to "escape" the potent antinatriuretic actions of ANG II and to return Na excretion to normal via the pressure natriuresis mechanism.
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PMID:Control of sodium excretion by angiotensin II: intrarenal mechanisms and blood pressure regulation. 352 37

Angiotensin II, if injected into the lateral ventricles of rabbits in doses of 0.015-0.15 microgram, has an inhibitory action on the fear response evoked by electrical stimulation of the ventromedial hypothalamic nucleus, but in doses of 1-10 ng it blocks the inborn behavioral fear responses in rats. On microionophoretic application of angiotensin II to single neurons in the cerebral cortex and parafascicular complex of the thalamus, predominantly activation responses were observed. Predominance of inhibitory neuronal responses were noted in structures of the hypothalamus and mesencephalic reticular formation to angiotensin II. Responses of cortical and subcortical neurons to angiotensin II are potentiated after stimulation of the "fear center" in the ventromedial hypothalamus. The hypothesis was put forward that depression of the fear response after administration of angiotensin II is connected with changes in cortico-subcortical relations, during which ascending activating influences of the mesencephalic reticular formation on the cerebral cortex are abolished due to descending influences of cortical and thalamic neurons.
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PMID:Angiotensin II as a factor inhibiting the fear response. 360 Oct 59

Investigations into the site of vasodilator and antivasoconstrictor activity of calcium antagonists previously performed in cats were extended to a second species, barbiturate-anaesthetized rabbits, and a second vasoconstrictor agent, vasopressin. The dihydropyridine derivative darodipine (code name PY 108-068; 10, 30 and 100 micrograms kg-1 i.v.) showed systemic haemodynamic effects comparable to those seen in cats at half these doses. Darodipine effected regional vasodilatation (measured with tracer microspheres) in the heart, brain and skeletal muscles as in cats. Only the vessels of the adrenals (dilated in rabbits but not in cats), and the kidneys and skin (constricted in rabbits but not in cats) responded differently to darodipine. Angiotensin II (A II; 0.15 and 1.5 micrograms kg-1 min-1) constricted the same vascular beds in rabbits as in cats, namely the heart, kidneys, small intestine, pancreas, spleen, skin and arterio-venous shunts (inferred from microspheres reaching the lungs), the only exceptions being the vessels of the stomach and liver (constriction only in cats) and the adrenals (constriction only in rabbits). Darodipine (30 and 100 micrograms kg-1) attenuated the A II-induced vasoconstriction in the same vascular beds in rabbits as in cats including the kidneys, which were constricted after administration of the antagonist alone. These results indicate surprisingly small species differences for the vasodilator effects of darodipine as well as the attenuation of the vasoconstrictor effects of A II. Lysine-vasopressin (2 and 50 mu kg-1 min-1) did not increase blood pressure in anaesthetized rabbits but dose-dependently lowered heart rate, cardiac output, total peripheral conductance and myocardial contractile force (measured with a strain gauge). Vasopressin constricted all peripheral vascular beds dose-dependently, except for those of the kidney and liver. The effects of vasopressin persisted in the animals infused with placebo solution. Darodipine (30 and 100 micrograms kg-1), but not verapamil (300 and 1000 micrograms kg-1) reversed the vasopressin-induced cardiac depression and decrease in cardiac output. This probably also explains most of the apparent differences between the effects of the two calcium antagonists on the peripheral circulation. Both calcium antagonists diminished the vasopressin constriction in most vascular beds except those of the spleen, skin and arterio-venous shunts. Most of the effects were dose-related but not strictly competitive, as far as this can be judged based on two doses of agonist and antagonist. 9 As with A II the effects of vasopressin were diminished in vascular beds not normally dilated by calcium antagonists. 10 Calcium antagonists display two typical patterns of activity. The vasodilator pattern consists of dilatation of the vesels of the heart, brain and, to a degree varying with the agents, skeletal muscle. The antivasoconstrictor effects occur in some but not all of the vessels constricted by the constrictor agent, vasoconstriction of the spleen, skin and arterio-venous shunts being resistant to the action of calcium antagonists. The pattern of antivasoconstrictor activity appears to depend on the constrictor compound used, inasmuch as such agents constrict different vascular beds.
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PMID:Modification of vasopressin- and angiotensin II- induced changes by calcium antagonists in the peripheral circulation of anaesthetized rabbits. 402 74

In the neonatal rat spinal cord slice preparation responses of the dorsal horn interneurons to iontophoretic or bath application of methionine-enkephalin (ME), substance P (SP) and somatostatin (SS) were qualitatively similar to those obtained in intact spinal cord. Thus, SP powerfully excited almost all neurons tested (15/16), while ME and SS depressed neuronal discharges in 13/14 and 4/6 units respectively. In some dorsal horn neurons the iontophoretic application of ME caused a marked depression of the SP-induced excitation. Angiotensin II (AgII) had no effect on dorsal horn units (n = 8). In the slices perfused with a Ca2+-free, Mg2+-high Krebs solution the extracellularly recorded effects of ME, SP and SS were not significantly modified, suggesting that the peptides were acting directly on postsynaptic sites. The results also indicate that the in vitro rat spinal cord slice preparation can be successfully utilized for further studies on the cellular mechanisms of actions of neuropeptides, particularly in relation to synaptic transmission processes in the dorsal horn.
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PMID:Neonatal rat spinal cord slice preparation: postsynaptic effects of neuropeptides on dorsal horn neurons. 616 14

Angiotensin II (AII) receptors in guinea pig isolated esophageal muscularis mucosae (EMM), stomach fundus, gall bladder, ileum, colon and thoracic aorta have been characterized by peptide agonists and nonpeptide antagonists in the presence of peptidase inhibitors. Angiotensin peptides contracted every preparation studied; the potency order typically was [Sar1]AII > or = AII > angiotensin III (AIII) > or = [Val4]AIII >> AI >>> [des Phe8]AII. AI was ineffective everywhere except the gall bladder, where it acted as a full agonist. Tetrodotoxin (1 microM) and atropine (1 microM) did not affect the AII response in EMM, fundus and gall bladder. In ileum, AII and AIII were equieffective, and both the maximal response and potency were decreased by tetrodotoxin and atropine. Indomethacin (3 microM) abolished response to AII in the fundus but had little effect on the gall bladder and the atropine-resistant component of the ileal response. The AT1-selective antagonist losartan (DuP 753) antagonized responses to AII in all tissues with similar affinities when there was no depression of maximal response (pKB = approximately 8-8.3). The AT2-selective antagonist PD123177 (10 microM) failed to antagonize responses to AII in any tissue. These data suggest the presence of AT1 receptors in intestinal and vascular smooth muscles of the guinea pig. It is unclear whether all AT1 receptors are similar because of the differential potency order observed in the presence of peptidase inhibitors. Of the isolated tissue investigated, responses to AII are robust and reproducible in the ileum, fundus and gall bladder.
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PMID:Characterization of angiotensin II receptors in smooth muscle preparations of the guinea pig in vitro. 826 14


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