Characterization of postsynaptic alpha-adrenergic receptors by [3H]-dihydroergocryptine binding in muscular arteries from the rat mesentery.

Colucci, Wilson S.; Gimbrone, Michael A.; Alexander, R. Wayne

doi:10.1161/01.hyp.2.2.149

Cited by 26 publications

(12 citation statements)

References 32 publications

(11 reference statements)

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“…These results, however, are in agreement with the characterization of CY receptors in the rat mesenteric arteries (Colucci et al, 1980). The mitogenic action of epinephrine was observed even a t M, a physiological concentration for the rat (Buhler et al, 1978).…”

Section: Epi Episupporting

confidence: 84%

Growth‐stimulating effect of catecholamines on rat aortic smooth muscle cells in culture

Blaes

Boissel

1983

Journal Cellular Physiology

164

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The effect of epinephrine was tested on the proliferation of rat arterial smooth muscle cells (SMC) in secondary cultures. Epinephrine added daily to the culture medium caused a striking stimulation of growth. The effect increased with time and was dose-dependent. Maximal stimulation was observed at a concentration of 10(-5) M and after 72 hours. At higher concentrations (10(-3) M) epinephrine exhibited toxic effects on SMC. When SMC were maintained quiescent by deprivation of serum, the subsequent addition of epinephrine required serum to significantly enhance growth. This growth stimulation increased with serum concentration (from 0.1% to 10%). All the adrenergic agonists tested were found to stimulate SMC growth, with an activity classified by decreasing order as follows: norepinephrine greater than epinephrine greater than isoproterenol. Finally, this mitogenic response of SMC to catecholamines was specific since it could be blocked by adrenergic blocking agents, phentolamine being more efficient than propranolol in that connection. The results suggest that epinephrine and other catecholamines may act as growth factors for aortic SMC, at least in rat, mostly through adrenoreceptors.

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Section: Epi Episupporting

confidence: 84%

Growth‐stimulating effect of catecholamines on rat aortic smooth muscle cells in culture

Blaes

Boissel

1983

Journal Cellular Physiology

164

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“…The specific binding of 3H prazosin to the membranes preparations was rapid, reversible, saturable and of high affinity (Kd=0.19 nM) and involved a single class of binding sites. Kd values presented here with 3H-prazosin was lower than those obtained with 3H-WB4101 (4) or 3H dihydroergocryptine (3,5), indicating a more specific binding of prazosin to at-adre noceptors of this preparation. Although the preparation of the membrane fraction from the brain was conducted essentially in a conventional way, the values of Bmax obtained from the brain in this study were slightly lower than those described in other publications.…”

Section: Resultscontrasting

confidence: 65%

Displacement by α-Adrenergic Agonists and Antagonists of 3H-Prazosin Bound to the α-Adrenoceptors of the Dog Aorta and the Rat Brain

Nagatomo

Tsuchihashi

Sasaki

et al. 1985

Japanese Journal of Pharmacology

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Abstract-To characterize the a,-adrenoceptors in the dog aorta and the rat brain and to assess the antagonistic potencies of various chemicals inclusive of newly synthesized ones, radioligand binding assays were performed, and the potencies thus obtained were compared with those obtained from pharmacological obser vations.Reproducible binding to and displacement from the dog aorta of 3H prazosin were observed.The rank orders of the inhibition of 3H-prazosin binding to the membrane preparations of the aorta expressed as IC50 (the concentration of drugs inhibiting 50% of maximal specific binding of 3H-prazosin) were: prazosin> YM09538 > phentolamine > yohimbine > phenoxybenzamine > labetalol >S-596> dibenamine > K-351 > propranolol > hydralazine > N-696 for a-blockers and ( epinephrine > clonidine > I-norepinephrine > phenylephrine > 1-isoproterenol for agonists.IC50 values of phenoxybenzamine, labetalol, dibenamine and K-351 obtained in the brain preparations were higher than those obtained in the pre paration of the aorta. There was a good correlation (r=0.90) between the IC50 values obtained in the dog aorta and in the rat brain, suggesting that the a, -adrenergic receptors in the dog aorta and the rat brain resemble each other. Good correlations (aorta, r=0.97 and brain, r=0.94) were also observed between IC50 values derived from the binding assay in the aorta or the brain and the pA2 values obtained as regards to the contractile response of the rat aorta to phenylephrine.Thus, this method could be useful for the assessment of newly synthesized chemicals as a adrenergic antagonists.

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“…Changes in receptor number are not necessarily a generalized phenomenon and localized changes in adrenoceptor number in specific brain regions have been reported. 9 Unfortunately, although others have reported binding studies in vascular membranes from the rat 22 and dog, 23 we have been unable to determine specific a-adrenoceptor binding with [ Although no hypertension-related change in a-adrenoceptor binding was observed, specific prazosin binding was decreased in all tissues examined in both hypertensive and normotensive animals from the older group. These animals would be 24-30 weeks old compared to 10-14 weeks in the case of the younger group.…”

Section: Discussionmentioning

confidence: 83%

Alpha adrenoceptors and autonomic mechanisms in perinephritis hypertension in the rabbit.

Hamilton¹,

Reid²

1983

Hypertension

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SUMMARY Increased pressor responses to norepinephrine and other pressor agents have been reported to occur in human essential hypertension and in several animal models of experimental hypertension. These increased responses might be related to the development of hypertension or could be a secondary consequence of the elevation in blood pressure. We have examined pressor responses to alpha-adrenoceptor agonists and to angiotensin II in male New Zealand White rabbits with perinephritic hypertension. Increased pressor responses were observed for the a, adrenoceptor agonist phenylephrine and the mixed a r /a 2 -adrenoceptor agonist norepinephrine but not for the « 2 adrenoceptor selective agonist guanabenz or angiotensin II. The increase occurred within 7 days of surgery and in some animals was observed when mean arterial pressure was not significantly elevated. It could not readily be attributed to intimal thickening or hypertrophy of the arterial wall, altered basal levels of norepinephrine or epinephrine, changes in norepinephrine clearance, /3-adrenoceptor interactions, or decreased baroreceptor sensitivity. However, the possibility that vascular hypertrophy and decreased baroreflex sensitivity may contribute to the increase at later times cannot be excluded. In all tissues examined, specific prazosin binding was decreased in the older animals and specific clonidine binding was decreased in forebrain. However, these changes were observed In both hypertensive and sham-operated animals and were probably age-related. We believe the increased response to a,-adrenoceptor agonists may be related to changes at a postreceptor site in the coupling of receptor activation to smooth muscle contraction. 1 " 2 Similar observations have been made in animal models of experimental hypertension including spontaneously hypertensive rats 3 and renal hypertensive rabbits. 4 5 Changes in norepinephrine responsiveness may be mediated by /3-receptors, classical postsynaptic a,-adrenoceptors, the presynaptic regulatory a 2 -adrenoceptors, or the recently proposed postsynaptic aj-adrenoceptor 6 ' 7 which may participate in regulation of peripheral resistance. Increased responses to norepinephrine could also be the result of changes in the number of adrenoceptors or their affinity for the neurotransmitter or alternatively secondary to structural changes in the vessel wall. Changes in a-adrenoceptor number have been observed in several brain regions from spontaneously

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Characterization of postsynaptic alpha-adrenergic receptors by [3H]-dihydroergocryptine binding in muscular arteries from the rat mesentery.

Cited by 26 publications

References 32 publications

Growth‐stimulating effect of catecholamines on rat aortic smooth muscle cells in culture

Growth‐stimulating effect of catecholamines on rat aortic smooth muscle cells in culture

Displacement by α-Adrenergic Agonists and Antagonists of 3H-Prazosin Bound to the α-Adrenoceptors of the Dog Aorta and the Rat Brain

Alpha adrenoceptors and autonomic mechanisms in perinephritis hypertension in the rabbit.

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