Identification of alpha1 adrenergic receptors in rabbit aorta with [125I]BE2254

Tsujimoto, Gozoh; Bristow, Michael R.; Hoffman, Brian B.

doi:10.1016/0024-3205(84)90227-3

Cited by 16 publications

(5 citation statements)

References 21 publications

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“…On the basis that noradrenaline has equal affinity for the a,-adrenoceptors present in the two preparations (Docherty et al 1981;Digges & Summers 1983) and that the apparent dissociation constant (KD) is approximately 4 x mol/l (Tsujimoto et al 1984), it is apparent that noradrenaline has a high efficacy and consequently only has to occupy a small percentage of receptors to produce a response (i.e., it is likely that noradrenaline has a receptor reserve).…”

Section: G a Mcpherson Et Almentioning

confidence: 99%

EFFECTS OF PHENOXYBENZAMINE ON RESPONSES TO SOME RECEPTOR AGONISTS AND CALCIUM IN VITRO

McPherson¹,

Krstew²,

Malta³

1985

Clin Exp Pharma Physio

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Noradrenaline-induced contractions of the rabbit and rat isolated aorta and guinea-pig spleen strips were inhibited by concentrations of phenoxybenzamine which did not affect responses to calcium. This may suggest a specific action on alpha-adrenoceptors. However, analysis of noradrenaline concentration-effect curves in guinea-pig spleen indicated that 1 mumol/l phenoxybenzamine should have reduced the available receptor population to 6% of control, but data from radioligand binding experiments on the same tissues using [3H]-prazosin indicated a reduction of the receptor population to only 82% of control. The reduced responsiveness observed in the organ bath study after phenoxybenzamine pretreatment, whilst not apparently related to effects on voltage-dependent calcium channels, could be due to the actions of phenoxybenzamine on other (non-receptor) processes such as receptor-operated calcium channels. Maximal contractile responses to histamine in rabbit isolated aorta but not those in guinea-pig isolated ileal preparations, were depressed by concentrations of phenoxybenzamine which depressed responses to calcium. Phenoxybenzamine produced parallel rightward shifts of curves to carbachol in guinea-pig ileal preparations but only depressed maximal responses to the agonist in higher concentrations which reduced responses to calcium. On the basis of the results obtained with calcium it is possible that the effects of phenoxybenzamine on receptor-mediated responses could be produced through the actions of this antagonist at less specific sites such as voltage-dependent calcium channels for histamine in rabbit aorta and carbachol in guinea-pig ileum. For alpha-receptor mediated responses in aortic and splenic strip preparations and for histamine-mediated responses in guinea-pig ileum, the actions of phenoxybenzamine may reflect an interaction of the antagonist with receptor-operated calcium channels.

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Section: G a Mcpherson Et Almentioning

confidence: 99%

EFFECTS OF PHENOXYBENZAMINE ON RESPONSES TO SOME RECEPTOR AGONISTS AND CALCIUM IN VITRO

McPherson¹,

Krstew²,

Malta³

1985

Clin Exp Pharma Physio

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“…Effects of a1-adrenoceptor subtype selective antagonists CEC and WB4101 on noradrenalineinduced contractile response, phosphoinositides (PI) hydrolysis and [125I]-BE2254 binding sites were examined in rabbit aorta ring segments. (Tsujimoto et al, 1984(Tsujimoto et al, , 1989.…”

Section: Methodsmentioning

confidence: 99%

“…[12sI]-BE2254 binding [1251I]-BE2254 binding experiments in rabbit aorta particulate membrane fraction were performed as described previously (Tsujimoto et al ,1984).…”

Section: Measurement Of [3h]-pi Hydrolysismentioning

confidence: 99%

Different desensitization mechanisms of two alpha 1‐adrenoceptor subtypes in the contraction of rabbit aorta.

Suzuki

Tsujimoto

Hashimoto

1990

Brit J Clinical Pharma

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Using a1-adrenoceptor selective antagonists chlorethylclonidine (CEC) and WB4101, both functional and radioligand binding studies showed that rabbit aorta contains at least two pharmacologically distinct a1-adrenoceptor subtypes of approximately 10% ala and 90% alb receptors, and that each receptor subtype has a distinct role in the a1-adrenoceptor-mediated vasoconstrictive response through different biochemical mechanisms for increasing intracellular Ca2+; ala receptors cause tonic response predominantly dependent on the influx of extracellular Ca2 , while alb receptors stimulate phosphoinositides (PI) hydrolysis/intracellular Ca2+ mobilization and cause phasic response mainly independent of extracellular Ca2 . Incubation of rabbit aorta with 10 FM noradrenaline (NA) for 2 h resulted in a reduction in the phasic response and PI hydrolysis to NA with no change in the tonic response. Similar to the NA incubation, the protein kinase C stimulator PMA (1 FM) selectively attenuated aOb-receptor mediated PI hydrolysis and phasic contraction but had little effect on a la-receptor-mediated tonic response. The protein kinase C inhibitor H-7 (10 FM) blocked these inhibitory effects of PMA. Treatment with H-7 (10 FJM) prevented the NA-induced alb receptor desensitization in inositol monophosphate (IP) formation and phasic response. The results suggest that activation of C kinase may be involved in the development of selective desensitization of alb receptors by a short-time in vitro incubation of NA.

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“…Binding of [125I|BE2254 [125I]BE2254 is considered to be a selective highaffinity radioligand for the study of ,-adrenergic receptors (Tsujimoto, Bristow & Hoffman, 1984); fur¬ thermore, it is thought to have similar potencies for both a, receptor subtypes (Han et al 1987). For the ,-adrenergic receptor studies, crude particulate fractions were prepared as described by Tsujimoto et al (1989) with slight modifications, and were used immediately in the receptor-binding assays.…”

Section: Animalsmentioning

confidence: 99%

“…Measurement of specific [l25I]BE2254 binding was usually performed by incubating 100 µ membrane preparation with [125I]BE2254 in a total volume of 150 µ for 20 min at 37°C (Tsujimoto et al 1984). …”

Section: Animalsmentioning

confidence: 99%

Thyrotrophin increases the α1b-adrenergic receptors in rat thyroid gland in vivo

Shimura

Endo²,

Onaya³

1990

Journal of Endocrinology

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Using chlorethylclonidine (CEC), an alpha 1b-adrenergic receptor-selective antagonist, we characterized alpha 1-adrenoceptor subtypes in rat thyroid gland, and investigated the effect of methimazole (MMI)-induced high TSH levels on alpha 1 receptor subtypes and noradrenaline-induced iodide organification. The density of thyroid alpha 1-adrenergic receptors was increased about sixfold in rats treated with MMI for 3 weeks compared with controls. Pretreatment of thyroid membrane preparations with CEC (10 mumol/l) caused an 83% decrease in specific 2-[beta-(hydroxy-3-[125I]iodophenyl) ethylaminomethyl]tetralone binding sites in MMI-treated rats, but only a 43% decrease in control rats. The density of CEC-insensitive alpha 1 receptors (alpha 1a) was similar in MMI-treated and control rats, so MMI was shown to increase CEC-sensitive alpha 1 receptors (alpha 1b). Noradrenaline-stimulated iodide organification was threefold greater in MMI-treated rats than in control rats when values were expressed as a per cent increase over basal levels. Pretreatment of thyroid lobes with 10 mumol CEC/l for 30 min caused a 66% decrease in maximal noradrenaline-induced iodide organification in MMI-treated rats, but a significantly lower decrease (49%) in control rats. These results suggest that the rat thyroid gland contains both alpha 1a and alpha 1b receptors, both of which mediate noradrenaline-induced iodide organification, and also that TSH enhances noradrenaline-induced iodide organification by increasing alpha 1b receptor density.

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Identification of alpha1 adrenergic receptors in rabbit aorta with [125I]BE2254

Cited by 16 publications

References 21 publications

EFFECTS OF PHENOXYBENZAMINE ON RESPONSES TO SOME RECEPTOR AGONISTS AND CALCIUM IN VITRO

EFFECTS OF PHENOXYBENZAMINE ON RESPONSES TO SOME RECEPTOR AGONISTS AND CALCIUM IN VITRO

Different desensitization mechanisms of two alpha 1‐adrenoceptor subtypes in the contraction of rabbit aorta.

Thyrotrophin increases the α1b-adrenergic receptors in rat thyroid gland in vivo

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