Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.11.18 (MAP)
 7,412 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We investigated hemodynamic actions of endothelin (ET) in conscious rats. Intravenous injections of ET produced dose-dependent biphasic blood pressure (MAP) responses: initial decreases of up to 84 +/- 11 s were followed by increases of up to 1-h duration. Corresponding responses in cardiac output (CO), heart rate, and efferent splanchnic nerve activity were reciprocal to changes in MAP. Mesenteric blood flow showed an immediate and sustained decrease. Compared with equidepressor doses of sodium nitroprusside (NNP), ET produced a markedly different regional hemodynamic response pattern during the initial depressor phase. Compared with equipressor doses of the alpha-adrenoceptor agonist methoxamine, ET produced significantly greater vasoconstriction in hindlimb and renal vascular bed during pressor phase. ET-induced changes in CO were significantly greater than the respective CO responses to NNP and methoxamine in intact animals and following cardiac autonomic blockade with atenolol and methscopolamine. ET has vasodilator and vasoconstrictor properties that induce a unique hemodynamic response pattern on intravenous injection. Persistence of ET-induced changes in CO following cardiac autonomic blockade suggests direct cardiostimulatory actions of the peptide during depressor phase as well as direct cardiodepressant actions during pressor phase.
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PMID:Hemodynamic actions of intravenous endothelin in rats: comparison with sodium nitroprusside and methoxamine. 217 44

Blood pressure (BP) becomes more sodium and body fluid sensitive as renal function deteriorates. Thus, hypertension in chronic renal failure is mostly of the sodium sensitive type. We studied whether the increased sodium sensitivity (SS) can be restored to normal on the maintenance phase of hemodialysis (HD) therapy. Body weight (BW) and BP (specifically, mean arterial pressure [MAP]) were measured after HD and before the next HD, and the body fluid sensitivity (BFS) was calculated as the ratio of changes in these factors on both introduction and maintenance phases in HD patients (n = 56) who were not taking any antihypertensive drugs (BFS = delta MAP/delta BW). In a preliminary study, the amount of interdialytic sodium intake (QNa+) was measured (n = 30), and SS was calculated as the ratio of the change in MAP to QNa+ (SS = delta MAP/QNa+). Interdialytic BW gain (3.1 +/- 0.1 kg) was correlated with the amount of sodium intake (136 +/- 17 mEq), resulting in a positive relationship between BFS and SS (r = 0.79, P less than .0001). Therefore, BFS was used as an index of SS. As a whole, BFS decreased from the introduction to the maintenance phase (6.5 +/- 1.0 to 3.5 +/- 0.6 mm Hg/L, P less than .01). This decrease was marked (6.2 +/- 1.1 to 2.9 +/- 0.6 mm Hg/L, P less than .01) in patients (n = 46) whose BP was normalized in the maintenance phase, while not significant (7.9 +/- 1.9 to 6.3 +/- 1.3 mm Hg/L) in patients (n = 10) whose BP was still high.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Normalization of increased sodium sensitivity by maintenance hemodialysis. 222 54

The cardiac and hemodynamic effects of 3 doses (0.1, 0.3 and 1 mg/kg, iv) of spiraprilat, the diacid active metabolite of the new angiotensin I converting enzyme inhibitor spirapril, have been investigated and compared to those of saline in chronically implanted conscious dogs at rest. Under a normal sodium diet, spiraprilat, 1 mg/kg, induced significant (at least P less than 0.05) decreases in mean arterial pressure (MAP, -11%), total peripheral resistance (TPR, -21%), left ventricular end diastolic pressure (LVEDP, -15%) and increases in heart rate (HR, +12%) and cardiac output (CO, +16%) whereas dP/dtmax remained unchanged. Spiraprilat-induced tachycardia was not modified by propranolol pre-treatment but was abolished by previous administration of the propranolol-N-methylatropine combination. Spiraprilat, 0.1 mg/kg, did not affect any parameter, but spiraprilat, 0.3 mg/kg, showed intermediate effects. Finally, sodium depletion strongly potentiated spiraprilat effects on MAP, TPR, LVEDP, HR and CO. We conclude that: a), in conscious dogs under normal sodium diet, spiraprilat reduces TPR and MAP through peripheral vasodilating properties; b), spiraprilat-induced tachycardia is mainly related to parasympathetic tone withdrawal, possibly in relation with high and low pressure baroreceptors deactivation; and c), sodium depletion considerably potentiates spiraprilat cardiac and hemodynamic effects.
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PMID:Hemodynamic and cardiac effects of spiraprilat in normal and sodium depleted conscious dogs. 228 46

We evaluated the effect of acute unilateral renal denervation (DNX) on the tubuloglomerular feedback (TGF) mechanism in Inactin-anesthetized hydropenic male 8- to 10-wk-old spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY). SHR had higher mean arterial pressure (MAP, 28%) and renal vascular resistance (RVR, 35%), whereas renal blood flow (RBF), glomerular filtration rate (GFR), urine flow, and sodium excretion were similar. DNX in SHR did not change MAP but decreased RVR (26%) and increased RBF (29%), GFR (16%), urine flow (52%), and sodium excretion (431%). DNX did not affect these in WKY. Loop of Henle perfusion with Ringer solution reduced early proximal flow rate (EPFR) in SHR more than in WKY; significantly different at a loop flow of 20 nl/min (9.8 +/- 0.7 vs. 6.5 +/- 0.7 nl/min). DNX in SHR increased the nonperfused EPFR from 25.6 +/- 1.1 to 31.7 +/- 1.3 nl/min and reduced TGF responses during perfusion at both 20 nl/min (9.8 +/- 0.7 vs. 4.4 +/- 0.7 nl/min) and 40 nl/min (14.2 +/- 1.1 vs. 10.4 +/- 0.7 nl/min). TGF sensitivity was attenuated by DNX, as indicated by reduced maximum reactivity (-0.89 +/- 0.14 to -0.36 +/- 0.07) and increased turning point (16.5 +/- 0.9 to 25.2 +/- 2.9 nl/min). TGF responses in WKY were not influenced by DNX. Sham denervation did not alter renal hemodynamics and TGF. These results indicate that renal nerves exert a tonic influence on the renal vasculature and the TGF system in SHR but not in WKY. Enhanced TGF responsiveness may be involved in volume retention and in the maintenance of hypertension in SHR.
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PMID:Attenuation of enhanced tubuloglomerular feedback activity in SHR by renal denervation. 233 Sep 89

In the present study we investigated the effect of anteroventral third ventricle (AV3V) lesion on pressor, dipsogenic and natriuretic responses produced by the intracerebroventricular (i.c.v.) injection of a cholinergic agonist (carbachol). Freely moving rats with AV3V or sham lesion (1-2 days and 9-12 days) and a delay cannula implanted into the lateral ventricle were studied. Changes in mean arterial pressure (MAP, 1 h record), water intake (1 h) and Na+ excretion (2 h) were analysed after i.c.v. injection of carbachol (7.5 nmol). In sham rats, i.c.v. injection of carbachol produced an increase in MAP (35 +/- 2 mmHg), water ingestion (7.7 +/- 1.2 ml/h) and Na+ excretion (626 +/- 42 microEq/120 min). The effects of i.c.v. carbachol injection were reduced 1-2 days after AV3V lesion (delta MAP = 6 +/- 2 mmHg, water ingestion = 0.3 +/- 0.3 ml/h and Na+ excretion = 31 +/- 11 microEq/120 min) and 9-12 days (delta MAP = 11 +/- 3 mmHg, water ingestion = 3.3 +/- 0.9 ml/h and Na+ excretion = 37 +/- 11 microEq/120 min). These results show that the AV3V region is essential for the full development of the pressor, dipsogenic and natriuretic responses produced by central cholinergic receptors.
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PMID:The anteroventral third ventricle (AV3V) region is essential for pressor, dipsogenic and natriuretic responses to central carbachol. 238 68

In conscious dogs, we examined the hypothesis that the effects of atrial natriuretic peptide (ANP) are mediated by cyclic GMP and tested whether stimulation of the intracellular pathway beyond the ANP receptor level still exerts ANP-like effects during tolerance to ANP in heart failure. We studied the hemodynamic, renal, and hormonal effects of the cyclic GMP analogue 8-bromo-cyclic GMP (8-Br-cyclic GMP) in conscious dogs before and after induction of congestive heart failure by right ventricular pacing. In healthy dogs, 8-Br-cyclic GMP (1-100 micrograms/kg/min) dose-dependently decreased mean arterial pressure (MAP -19% by 100 micrograms/kg/min) and total peripheral resistance (TPR -22%) with no change in cardiac output (CO) and right atrial pressure, increased urine flow (UF 52%), and sodium excretion (UNaV 135%). Plasma renin (62%) and norepinephrine (NE 24%) were increased. In dogs with heart failure, 8-Br-cyclic GMP induced a similar arteriolar dilation (MAP -16%, TPR -23%) with no change in CO and preload. However, the effects on renal excretory function were abolished or markedly attenuated (UF -4%, UNaV 7%). Plasma renin (163%) and aldosterone (40%) were increased. Our findings support the hypothesis that the renal effects of ANP are mediated by cyclic GMP in vivo. The attenuation of renal effects of 8-Br-cyclic GMP in heart failure does not prove but is in agreement with the hypothesis that an intracellular defect beyond cyclic GMP production might be involved in the tolerance to ANP in heart failure.
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PMID:Hemodynamic, renal, and hormonal effects of 8-Br-cyclic GMP in conscious dogs with and without congestive heart failure. 247 97

Several processes participate in the clearance of atrial natriuretic peptide (ANP) from the circulation, one of which is enzymatic degradation. Endoprotease EC 3.4.24.11 (NEP 24.11), present within the kidney in high concentration, has been shown in vitro to degrade ANP. Phosphoramidon and thiorphan, two potent NEP 24.11 inhibitors, have been shown to prevent the enzymatic degradation of ANP. The purpose of the present study was to determine if phosphoramidon or thiorphan would alter the in vivo time course of the pharmacologic effects of ANP. The magnitude and duration of the ANP-induced increase in urine output and sodium and cyclic GMP excretion were examined with and without either thiorphan or phosphoramidon. Six separate groups of anesthetized rats received either a low, medium, or high infusion rate of thiorphan or phosphoramidon. Renal responses to ANP were potentiated and prolonged during the low phosphoramidon infusion (3 Ki) and the medium thiorphan infusion (150 Ki). At high inhibitor infusion rates in the anesthetized rat, ANP elicited a marked depressor response. In the conscious spontaneously hypertensive rat (SHR), a 15-min intravenous (i.v.) infusion of ANP (1 microgram/kg/min) lowered mean arterial pressure (MAP 23 +/- 6 mm Hg), with an approximately 35-min duration of action. A simultaneous i.v. infusion of phosphoramidon (high dose) produced both a potentiation (33 +/- 3 mm Hg) and a prolongation (greater than 65 min to return to baseline) of the depressor response. These data lend support to the hypothesis that enzymatic breakdown of ANP may play an important role in regulating the actions of atrial natriuretic peptide.
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PMID:Degradation of atrial natriuretic peptide: pharmacologic effects of protease EC 24.11 inhibition. 247 3

Kinesin from porcine brain was prepared by a procedure based on the strong binding of the protein to microtubules in the presence of sodium fluoride and ATP. The protocol reduces the requirement for taxol and AMP-PNP. The kinesin is active in terms of its ability to move microtubules on glass slides and its ATPase. The ATPase of this kinesin is about 8 nmol/min/mg; it is activated to 19 nmol/min/mg in the presence of microtubules. The relationship between gliding velocity and ATP concentration follows Michaelis-Menten kinetics. Using the motility assay, the maximal velocity is 0.78 micron/sec, and the Km value is 150 microM for ATP. For GTP the corresponding values are 0.38 micron/sec and 1.7 mM. ADP is a competitive inhibitor (Ki = 0.29 mM). Crude preparations of kinesin do not support motility on glass slides, whereas gel-filtered kinesin does. A search for potential inhibitory factors showed that one of them is MAP2; however, its inhibitory effect becomes visible only in certain conditions. MAP2 bound to microtubules does not inhibit kinesin-induced motility. However, when MAP2 and kinesin are preadsorbed to the glass surface independently of microtubules, MAP2 prevents the interaction of kinesin with microtubules, as if it formed a "lawn" that acted as a spacer and thus repelled the MAP-free microtubules or crosslinked the MAP-containing ones. The repelling effect of MAP2 domains (projection or assembly fragments obtained by chymotryptic cleavage) added separately is less pronounced and can be overcome by kinesin. These results reinforce the view of MAP2 as a spacer molecule.
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PMID:Interaction between kinesin, microtubules, and microtubule-associated protein 2. 253 84

The effect of hypoxic hypoxia (HH) and carbon monoxide hypoxia (COH) on adrenal medullary (MQ) and cortical (CQ) blood flow (radiolabeled microsphere technique) was studied in pentobarbital sodium-anesthetized, mechanically ventilated dogs. Animals were exposed to 60 min of hypoxia (arterial O2 content 8 vol%) induced by adding either nitrogen (HH, n = 6) or carbon monoxide (COH, n = 6) to the inspired gas. Whole adrenal Q and CQ increased by 70 and 50%, respectively, with HH but were unchanged during COH. MQ, however, increased threefold during both HH and COH. HH and COH both increased arterial levels of epinephrine, corticosteroids, and adrenocorticotropic hormone (ACTH). To determine whether the increase in CQ during HH was because of HH-induced increases in mean arterial blood pressure (MAP, approximately 20 mmHg), an additional group of animals (n = 6) was exposed to HH but had MAP maintained at control levels using a pressurized-bottle system. MAP control did not alter the CQ response to HH. We conclude that MQ appears to be associated with medullary secretory activity during hypoxia and that HH and COH stimulate adrenal medullary secretion equally. In contrast, CQ increases only with HH, despite similar increases in ACTH and corticosteroid levels during HH and COH, suggesting that an alternative mechanism is responsible for increased cortical blood flow during HH.
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PMID:Regional adrenal blood flow during hypoxia in anesthetized, ventilated dogs. 253 47

The purpose of this study was to observe the effects of opioid receptor and alpha-adrenergic receptors in the lower brain stem on the depressor response to electrical stimulation of renal afferent nerve, using intracisternal injection of blockers of these receptors. Experiments were conducted in sodium pentobarbital-anesthetized rabbits. The intracisternal injection (ict) of artificial cerebrospinal fluid (CSF) did not greatly affect the depressor response to stimulation of renal afferent nerve (RAS) and of aortic nerve (ANS). Ict of 550 nmol naloxone significantly inhibited the depressor response to RAS (P less than 0.05) but enhanced the depressor response to ANS (P less than 0.05). Ict of 335 nmol phentolamine significantly inhibited the depressor response to both RAS and ANS. Ict of naloxone reversed the phentolamine inhibition of the depressor response to ANS but did not affect the phentolamine inhibition of the depressor response to RAS. Ict of both naloxone and phentolamine did not affect the inhibitory interaction between the RAS-induced depressor and aortic baroreflex. Ict of phentolamine significantly decreased MAP, and ict of naloxone did not decrease MAP but reversed the decrease in MAP by ict of phentolamine. These data suggest that the activation of opioid receptors in the lower brain stem enhances the depressor response to RAS and attenuates the depressor response to ANS. Moreover, activation of alpha-adrenergic receptors in the lower brain stem facilitates the depressor response to RAS and ANS.
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PMID:[Effects of intracisternal injection of naloxone on the depressor response to stimulation of renal afferent nerve in rabbits]. 255 72


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