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Enhancement of vasoconstrictor response by a noncalcemic analogue of vitamin D3.

To clarify the effects of active vitamin D3 on pressor and vascular responses to vasoconstrictor substances, we studied pressor responses to the intravenous injection of norepinephrine or angiotensin II (Ang II) and vasoconstrictor responses to norepinephrine. Sprague-Dawley rats were given 1,25-dihydroxyvitamin D3 subcutaneously (200 ng/kg per day) for 14 days. The administration of 1,25-dihydroxyvitamin D3 augmented the pressor responses to norepinephrine and Ang II in conscious rats and was associated with a significant increase in serum calcium concentration (11.0 +/- 0.2 mg/dl). To further clarify whether the increased pressor response to vasoconstrictors may be due to the calcemic or direct action of active vitamin D3, we studied the effect of its noncalcemic analogue, 22-oxacalcitriol, and its inactive analogue, 24,25-dihydroxyvitamin D3, on the pressor response to vasoconstrictors in rats. The pressor responses to norepinephrine and Ang II were apparently augmented in 22-oxacalcitriol-treated rats similarly to 1,25-dihydroxyvitamin D3-treated rats. In contrast, the pressor responses were not affected by either 24,25-dihydroxyvitamin D3 or the intravenous infusion of calcium chloride. In an ex vivo experiment using a mesenteric preparation, the vascular sensitivity to norepinephrine was moderately augmented in rats treated with both 22-oxacalcitriol and 1,25-dihydroxyvitamin D3 but was not affected in rats treated with 24,25-dihydroxyvitamin D3. The results suggest that the enhanced pressor responses to norepinephrine and Ang II could be attributed to the direct effect of active vitamin D3 on vasculature rather than to hypercalcemia.

24,25-Dihydroxyvitamin D 3↗

Role of tyrosine kinase and PKC in the vasoconstrictor response to 20-HETE in renal arterioles.

The present study examined the hypothesis that activation of protein kinase C (PKC), components of the mitogen-activated protein (MAP) kinase pathway, or both contributes to the inhibitory effects of 20-hydroxyeicosatetraenoic acid (20-HETE) on K+-channel activity and its vasoconstrictor response in renal arterioles. 20-HETE (0.1 to 50 micromol/L) dose-dependently produced a 30% increase in PKC activity and a fivefold rise in the expression of active extracellular signal-regulated kinase 1 (ERK1) and ERK2 proteins in renal microvessels. 20-HETE (0.01 to 1 micromol/L) reduced the diameter of isolated perfused renal interlobular arterioles by 33+/-2%. Blockade of PKC activity with an N-myristoylated PKC pseudosubstrate inhibitor (Myr-PKCi, 100 micromol/L) or calphostin C (0.5 micromol/L) had no significant effect on the vasoconstrictor response to 20-HETE. In contrast, the tyrosine kinase inhibitors genistein (30 micromol/L) and tyrphostin 25 (10 micromol/L) reduced the response to 20-HETE by 76.5+/-2.1% and 67.5+/-1.8%, respectively. A specific inhibitor of mitogen-activated extracellular signal-regulated kinase (MEK), PD98059, had no effect on the vasoconstrictor response to 20-HETE. In cell-attached patches on renal vascular smooth muscle cells, 20-HETE reduced the open state probability of a large-conductance K+ channel (from 0.0026+/-0.0004 to 0.0006+/-0.0001). The Myr-PKCi (100 micromol/L) did not alter the inhibitory effects of 20-HETE on this channel. In contrast, the tyrosine kinase inhibitor genistein (30 micromol/L) blocked the inhibitory effects of 20-HETE on the large-conductance K+ channel. These data suggest that 20-HETE activates the MAP kinase system in renal arterioles and that the activation of a tyrosine kinase, which is proximal to MEK in this cascade, contributes to the inhibitory effects of 20-HETE on K+-channel activity and its vasoconstrictor effects in the renal arterioles.

Animals↗

Augmented responses to vasoconstrictor stimuli in hypercholesterolemic and atherosclerotic monkeys.

We examined effects of hypercholesterolemia and atherosclerosis on vasoconstrictor responses to norepinephrine and serotonin. Responses were compared in normal, atherosclerotic, and hypercholesterolemic but non-atherosclerotic cynomolgus monkeys. The hindlimb was perfused at constant flow so that changes in perfusion pressure indicated changes in vascular resistance. We measured the pressure gradient from the iliac to the dorsal pedal artery so that responses of the large artery segment could be determined. Serotonin decreased total hindlimb resistance in normal and hypercholesterolemic monkeys, but increased total resistance in atherosclerotic monkeys. There was a greater than 10-fold increase in constrictor responses of large arteries to serotonin in atherosclerotic monkeys, compared with normal and hypercholesterolemic monkeys. In contrast, we found that vasoconstrictor responses to norepinephrine are normal in atherosclerotic monkeys and increased in hypercholesterolemic monkeys prior to development of atherosclerosis. Hypercholesterolemia augmented responses of small vessels to norepinephrine. We conclude that, during early stages of hypercholesterolemia in cynomolgus monkeys, vasoconstrictor responses to norepinephrine are increased in small vessels. At a later stage, as atherosclerosis develops, responses to norepinephrine return to normal, but vasoconstrictor effects of large arteries to serotonin are greatly potentiated.

Animals↗

The central nervous system as a site of action for the coronary vasoconstrictor effect of digoxin.

Digitalis is known to have a vasoconstrictor effect in the coronary circulation. Recent studies have demonstrated that the coronary vasoconstrictor effects of acetylstrophanthidin and digoxin are neurally mediated via alpha adrenergic fibers. In the present study, experiments were done in 20 dogs anesthetized with chloralose and urethane to study the central nervous system as a possible site of action for this vasoconstrictor effect of digoxin. After the intravenous administration of 1.0 mg digoxin, cerebrospinal fluid concentrations of digoxin rose to a peak of 2.3+/-0.4 (SEM) ng/ml at 15 min, temporally corresponding to the peak in coronary vascular resistance change of +20.0+/-2.5% of control in the paced canine heart. Submicrogram digoxin injections into the lateral cerebral ventricle produced a significant increase in coronary vascular resistance, the latter injection producing a peak increase in coronary vascular resistance of 12.4+/-1.2% of control. Cross-perfusion experiments, where the isolated head of the operative dog was perfused from a donor dog receiving digoxin, thus keeping digoxin levels in the remainder of the operative dog very low, showed a similar degree of coronary vasoconstriction. Thus, the central nervous system appears to be an important site of action for the early coronary vasoconstrictor effect of digoxin.

Animals↗

Effects of insulin on vasoconstrictor responses to alpha agonist and tilting.

The effects of insulin on vasoconstrictor response were studied in diabetics without autonomic neuropathy. Vasoconstrictor response to phenylephrine was measured before and after insulin injection in 10 diabetics. Mean blood pressure, forearm blood flow, and forearm vascular resistance remained unchanged after insulin administration. But the increase in forearm vascular resistance to phenylephrine decreased significantly and heart rate increased significantly after insulin injection. In 9 diabetics, vasoconstrictor response to tilting was measured before and after insulin injection. Mean blood pressure, cardiac index, and the total peripheral resistance index remained unchanged after insulin administration. However, the increase in the total peripheral resistance index to tilting decreased significantly and heart rate increased significantly after insulin injection. Furthermore, a significant fall in mean blood pressure following tilting was observed only after insulin administration. Although blood glucose levels decreased significantly, no hypoglycemic symptoms occurred. The present study suggests that insulin inhibits vasoconstrictor responses to both alpha agonist and tilting in diabetics.

Adrenergic alpha-Agonists↗

[Autonomic reflexes: focusing on the arterial baroreceptor-vasoconstrictor reflex].

The arterial baroreceptor-sympathetic vasoconstrictor reflex (baroreceptor reflex), among autonomic reflexes, is summarized. Arterial baroreceptor afferents terminate in the caudal part of the nucleus tractus solitarius. Excitation of the baroreceptor afferents activates neurons in the caudal ventrolateral medulla that send axonal projections to the rostral ventrolateral medulla. These neurons (CVLM neurons) then inhibit tonic activity of sympathoexcitatory reticulospinal neurons in the rostral ventrolateral medulla (RVLM neurons). Tonic activity of RVLM neurons are responsible for tonic activity of the peripheral vasoconstrictors. These two kinds of neurons are essential neuronal components for the baroreceptor reflex. Both the neurons may also participate in various vasoconstrictor reflexes, such as the somato-and viscero-sympathetic vasoconstrictor reflexes.

Autonomic Nervous System↗

[Effects of phencyclidine analogs and phencyclidine/sigma ligands on vasoconstrictor response of rat mesenteric arteries induced by electrical field stimulation].

Using the model of perfused mesenteric arteries of rat, we studied the effect of phencyclidine (PCP), N-[1-(2-thienyl)cyclohexyl] piperidine (TCP), N,N-dimethylphenylcyclohexylamine (PCDA), N-(iso-propyl)-1-phenylcyclohexylamine (PCIPA), (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine maleate (MK-801), (+),(-)-N-allylnormetazocine (SKF 10 047), dextrorphan, and levorphanol on vasoconstrictor response induced by electrical field stimulation. PCP, TCP, PCDA, PCIPA, MK-801, levorphanol, and (-)-SKF 10 047 were found to increase the vasoconstrictor response in dose-dependent manner. The dose-effect curves of these compounds were similar to the curve of PCP. Although dextrorphan, an antagonist for PCP receptors, did not affect the vasoconstrictor response, it could non-competitively antagonize PCP's action. These studies suggest that some PCP analogs and PCP/sigma ligands may enhance the vasoconstrictor response induced by electrical field stimulation via action on PCP receptors.

Animals↗

Forearm vasoconstrictor response to ouabain: studies in patients with mild and moderate essential hypertension.

The dependence of arteriolar vasoconstrictor tone on the activity of Na+,K+-ATPase was studied in 17 normotensive subjects (NT) and 28 patients with essential hypertension (EH) by measuring the response in forearm blood flow and vascular resistance to intraarterial infusion of the Na+,K+-ATPase inhibitor ouabain. Basal plasma aldosterone concentrations were elevated in mild (n = 14) and moderate (n = 14) EH patients as compared with NT (p less than 0.001 for both) and correlated positively with intraarterial diastolic blood pressure (r = 0.551, p less than 0.001). Ouabain in incremental doses of 0.4-16 micrograms/100 ml tissue induced a vasoconstrictor response in the forearm with a maximal effect to 8 micrograms/100 ml tissue, which was not associated with an increase in regional noradrenaline release. The vasoconstrictor response to ouabain, 8 micrograms/100 ml, expressed as the percentage change in the ratio of forearm vascular resistance (FR) on the experimental side versus the control side, was 29.6 +/- 6.8% in NT (p less than 0.001); 51.9 +/- 8.4% in mild EH (p less than 0.001), and 36.0 +/- 12.7% in moderate EH (p less than 0.05). The vasoconstrictor response was greater (p less than 0.05) in patients with mild EH than in NT but did not differ in NT and patients with moderate EH. Vascular reactivity in the forearm, as assessed by intraarterial infusions of noradrenaline (3, 8, and 20 ng/min/100 ml tissue), did not differ in NT (n = 9) and patients with mild (n = 9) or moderate (n = 9) EH. The results suggest increased activity of arteriolar Na+,K+-ATPase in mild EH, which may represent a mechanism counteracting an accumulation of intracellular sodium and thereby an early increase in forearm vascular resistance (FR).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

Influence of nifedipine, verapamil and diltiazem on pulmonary vascular resistance and vasoconstrictors in cats.

In the present study, the effects of three classes of L-type calcium channel-blocking agents, nifedipine, verapamil and diltiazem, on the lobar arterial pressure and the vasoconstrictor responses in the pulmonary vascular bed were compared to those of cromakalim, a KATP channel activator, in the anaesthetized cat under controlled pulmonary blood flow and constant left atrial pressure. These drugs were infused intralobarly in doses selected which did not raise left atrial pressure, change cardiac output or alter systemic arterial pressure. Intralobar bolus injections of calcium channel-blocking agents and of the K+ channel activator decreased the lobar arterial pressure in a dose-related manner when pulmonary vasomotor tone was actively elevated by intralobar arterial infusion of U46619. The pulmonary vasodilator response to these agents was accompanied by a dose-related decrease of systemic arterial pressure. In decreasing lobar arterial pressure at elevated pulmonary vasomotor tone, the order of potency was nifedipine > verapamil > diltiazem, whereas in reducing systemic arterial pressure, the order of potency was nifedipine > diltiazem > verapamil. The calcium channel-blocking agents were less active than the reference drug, cromakalim, in both vascular beds. Intralobar arterial infusions of nifedipine, verapamil and diltiazem, at the rates of 0.03 mumol/min, 0.2 mumol/min and 0.1 mumol/min, respectively, caused no changes in cardiac output and in systemic and pulmonary arterial pressure. Infusion of all three calcium-channel-blocking agents blocked the pulmonary vasoconstrictor responses to BAY K 8644 (calcium entry promoter) and U46619 (thromboxane A2 mimic). Nifedipine infusion also reduced the pulmonary vasoconstrictor responses to methoxamine and BHT933 (alpha 1- and alpha 2-adrenoceptor agonists, respectively), whereas verapamil infusion reduced the responses only to methoxamine. Infusion of diltiazem caused no significant decrease of responses to either alpha-adrenoceptor agonist. The results of the present study suggest that the dihydropyridine, nifedipine, is more potent than the non-dihydropyridines, verapamil and diltiazem, in reducing the pulmonary vascular resistance and more effective in inhibiting the vasoconstrictor responses to the alpha-adrenoceptor agonists, to U46619 and to BAY K 8644 in the feline pulmonary circulation at the infusion rates which cause no or little hemodynamic changes.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗

Vasoconstrictors in facial plastic surgery.

The effectiveness of local anesthetics is improved by the addition of a vasoconstrictor with an increased duration of action and the ability to decrease both systemic toxic reactions and local bleeding. Epinephrine, the standard drug for vasoconstriction, has some limitations due to potential cardiac and local toxic effects. Using an animal model, we compared the effects of various concentrations of epinephrine and two other vasoconstrictors, phenylephrine hydrochloride and felypressin, on local blood flow. We also examined the local effects of bupivacaine hydrochloride and ropivacaine hydrochloride, a new local anesthetic. We found that felypressin was as effective a vasoconstrictor as epinephrine, with fewer potential toxic reactions. Phenylephrine (Neo-Synephrine), on the other hand, was less effective, with a shorter duration of action. As expected, bupivacaine produced vasodilation, while ropivacaine was found to have vasoconstrictive properties.

Amides↗

The use of vasoconstrictors in patients with cirrhosis: type 1 HRS and beyond.

In patients with cirrhosis and type 1 hepatorenal syndrome (HRS), systemic vasodilation, which is mainly attributable to splanchnic vasodilation, plays a critical role in the activation of endogenous vasoconstrictor systems, resulting in renal vasoconstriction and functional renal failure. It has been suggested that the use of splanchnic (and systemic) vasoconstrictors such as terlipressin (a vasopressin analog) or alpha-1-adrenoceptor agonists (midodrine or noradrenaline) may improve renal function in patients with type 1 HRS. Six studies (with only one randomized study in a small series of patients) have shown that terlipressin improves renal function in these patients. However, there is evidence that terlipressin alone may be less effective than terlipressin combined with intravenous albumin in improving renal function. Future randomized studies should confirm this difference and evaluate the impact of terlipressin therapy (with or without intravenous albumin) on survival. Interestingly, in nonrandomized studies, the use of alpha-1 agonists combined with other therapies (octreotide and albumin for midodrine; furosemide and albumin for noradrenaline) has been shown to improve renal function in patients with type 1 HRS. The efficacy and safety of combined therapies including alpha-1 agonists should be confirmed in randomized studies. Finally, preliminary evidence suggests that vasoconstrictor administration may be a novel therapeutic approach targeting vasodilation involved in the mechanism of: (1) renal failure in type 2 HRS; (2) paracentesis-induced circulatory dysfunction; and (3) arterial hypotension induced by byproducts of gram-negative bacteria. Further studies are needed in all these fields.

Adrenergic alpha-Agonists↗

Inhibition of furosemide-induced renin release by vasoconstrictors.

The effect of i.v. infused (asp1-beta-amid, val5)-angiotensin II (1.0 mug/kg min), octapressin (phe2, lys8-vasopressin) (10.0 mU/kg min) and of the alpha-sympathomimetic amine phenylephrine (40.0 mug/kg min) on the stimulation of renin secretion by furosemide (10.0 mg/kg i.v.) was investigated. The vasoconstrictors abolished the renin release induced by forosemide. Studies on the clearance of p-aminohippuric acid (PAH) (i.e. renal plasma flow) showed that the action of the vasoconstrictors cannot be explained by a decrease in access of furosemide to its intrarenal sites of action. The mechanism of the suppressive action of the vasoconstrictors on renin release is discussed.

Aminohippuric Acids↗

Direct positive inotropic and vasoconstrictor effects of endothelin.

Endothelin, a newly discovered vasoconstrictor peptide, when added to isolated cat papillary muscles, induced a direct positive inotropic effect that was slow in onset but of long duration. The magnitude of the developed force was concentration dependent. Endothelin exerted a marked concentration-dependent vasoconstriction in isolated cat carotid arteries and rabbit aortic rings. In both the carotid arteries and the aortic rings, endothelin induced a similar vasoconstrictor effect in the presence or absence of an intact endothelium. Addition of propyl gallate, a 5-lipoxygenase inhibitor, ibuprofen, a cyclooxygenase inhibitor, or SKF-525A, a cytochrome P450 inhibitor, at 2 microM did not significantly attenuate the ability of endothelin to vasoconstrict aortic rings in the presence or absence of an intact endothelium. These results demonstrate that the vasoconstrictor activity of endothelin operates independently of all three pathways of arachidonic acid metabolism (i.e., lipoxygenase, cyclooxygenase, or cytochrome P450 pathways) and is not dependent upon other endothelium-derived mediators (e.g., endothelium-derived relaxing factor, or eicosanoids) in these preparations. Moreover, endothelin exerts a direct positive inotropic effect in isolated cat ventricular myocardial tissue.

Animals↗

Cellular mechanism of action by a novel vasoconstrictor endothelin in cultured rat vascular smooth muscle cells.

Specific binding sites for synthetic porcine endothelin (pET), a novel potent vasoconstrictor peptide isolated from the supernatant of cultured porcine endothelial cells, and its effects on cytosolic free Ca2+ concentrations ([Ca2+]i) and phosphatidylinositol (PI) response were studied in cultured rat aortic vascular smooth muscle cells (VSMC). Binding of 125I-labeled-pET to rat VSMC was time- and temperature-dependent and the cell-bound 125I-labeled-pET was resistant to dissociate. Scatchard analysis of binding studies indicated the presence of a single class of high-affinity binding sites: the apparent Kd was 2-4 X 10(-10) M and the maximal binding capacity was 11,000-13,000 sites/cell. The binding was highly specific for pET because neither well-recognized vasoconstrictors, peptide neurotoxins, nor Ca2+-channel blockers affected the binding. pET dose-dependently (10(-9)-10(-7) M) induced a transient and sustained increase in [Ca2+]i in fura-2-loaded cells of which effect was largely dependent on extracellular Ca2+, whereas it had no significant effect on PI response in 3H-myoinositol-prelabeled cells. The present data clearly demonstrates the presence of specific receptors for pET distinct from those of the well-recognized vasoconstrictors and voltage-dependent Ca2+-channels in cultured rat VSMC, and suggest that pET-induced increase in [Ca2+]i is involved in the mechanism of its vasoconstriction.

Animals↗

Vasoconstrictor-induced protein-tyrosine phosphorylation in cultured vascular smooth muscle cells.

In cultured rat aortic smooth muscle cells, angiotensin II induced tyrosine phosphorylation of at least 9 proteins with molecular masses of 190, 117, 105, 82, 79, 77, 73, 45 and 40 kDa in time- and dose-dependent manners. Other vasoconstrictors such as [Arg]vasopressin, 5-hydroxytryptamine and norepinephrine induced the tyrosine phosphorylation of the same set of proteins as angiotensin II. The tyrosine phosphorylation of these proteins was mimicked by the protein kinase C-activating phorbol ester, phorbol 12 myristate 13-acetate, and the Ca2+ ionophore, ionomycin. These results demonstrate that the vasoconstrictors stimulate the tyrosine phosphorylation of several proteins in vascular smooth muscle cells and suggest that the tyrosine phosphorylation reactions are the events distal to the activation of protein kinase C and Ca2+ mobilization in the intracellular signalling pathways of the vasoconstrictors.

Angiotensin II↗

Drug interactions and vasoconstrictors used in local anesthetic solutions.

This study examined widely advertised interactions between sympathomimetic amine vasoconstrictors currently used in dental local anesthetic solutions and MAO inhibitors (phenelzine, 5 mg/kg), phenothiazines (chlorpromazine, 2 mg/kg), and tricyclic antidepressants (desipramine, 2 mg/kg). Twelve greyhound dogs premedicated with morphine and anesthetized with urethane and alpha-chloralose were prepared for physiologic recordings. During a control period, the dogs received bolus injections of epinephrine, norepinephrine, and levonordefrin sufficient to construct log-linear dose-response curves for each agent. Commercial anesthetic solutions, with and without the vasoconstrictors, were also used. The dose-response curves were then reproduced 1 hour after the administration of a drug interactant. Cardiovascular responses were not influenced by the coadministration of local anesthetics or by the prior administration of phenelzine. Chlorpromazine ameliorated pressor responses to norepinephrine and levonordephrin and reversed the hypertensive effect of high-dose epinephrine. Desipramine significantly increased vasoconstrictor potencies, particularly those of levonordefrin and norepinephrine, which were multiplied more than sixfold.

Anesthetics, Local↗

Vasoconstrictor response to prostacyclin in rabbit pulmonary circulation.

We have determined the effect of prostacyclin (PGI2) on segmental vascular resistance in rabbit lungs. Lungs of 26 rabbits were isolated and perfused with blood; 16 adult, greater than 6 months old, five juvenile, 6-8 week old and five neonatal, 2-3-week old. Six of the adult lungs were pretreated with indomethacin to block cyclooxygenase, prior to infusion of PGI2. In all lungs, flow was adjusted initially to keep pulmonary artery pressure approximately 20 cmH2O, left atrial and airway pressures being 8 and 6 cmH2O, respectively (zone 3), and then kept constant. We measured pulmonary artery pressure continuously and in the 10 untreated adult lungs, in which a vasoconstrictor response to PGI2 was obtained, we also measured pressures in 20-50 microns diameter subpleural arterioles and venules by the micropipette-servonulling method. We found that in juvenile and neonatal rabbit lungs, PGI2 did not change total vascular resistance significantly but in untreated adult lungs, it caused a significant increase in total vascular resistance only after a dose of 10 micrograms/kg. This age-related difference in vasoconstrictor response to PGI2 was not related to baseline total vascular resistance in the three groups of lungs. In adult lungs, vasoconstriction occurred mainly in arteries with a small effect in veins. Circulating levels of thromboxane B2, leukotriene C4, and 6-keto-PGF1 alpha increased following PGI2 infusion in adult lungs, whereas in neonatal lungs, only 6-keto-PGF1 alpha increased significantly. Indomethacin pretreatment completely abolished the vasoconstrictor response to PGI2. We conclude that PGI2-induced vasoconstriction is age and dose dependent in isolated rabbit lungs and that a cyclooxygenase product, such as thromboxane A2, may play a role in mediating the vasoconstriction.

Aging↗

Cerebral vasoconstrictor mediators.

Endogenous cerebral vasoconstrictor mediators regulate vascular resistance and blood flow in the brain as a whole and in various regions and participate in the pathogenesis of cerebral circulatory disturbances. Vasoconstrictors are effective in the treatment of diseases associated with cerebral vasodilatation. There are variations in the response of cerebral arteries from primate and subprimate mammals; therefore, information as to similarities and differences in their response is quite important in evaluating the physiological role, involvement in pathogenesis and therapeutic usefulness of the mediators in healthy men and patients. In this review we described characteristics of the action of vasoconstrictors (amines, peptides, prostanoids, and others) on isolated cerebral arteries from mammals, including humans and monkeys.

Animals↗