Functional characterization of a1-adrenoceptor subtypes in human subcutaneous resistance arteries

Yagna P.R. Jarajapu, Fiona Johnston, Colin Berry, Andrew Renwick, John C. McGrath, Allan MacDonald, Chris Hillier

Research output: Contribution to journalArticle

Abstract

The functional characteristics of the a1-adrenoceptor subtypes in human resistance arteries are still not clear. We recently reported that the a1A-adrenoceptor predominantly mediates contraction to norepinephrine in human skeletal muscle resistance arteries. In this study we extended these investigations to human subcutaneous resistance arteries. Arterial segments were isolated from the inguinal subcutaneous fat and mounted on a small vessel wire myograph. Potencies of agonists and antagonists were examined.N-[5-(4,5-dihydro-1H-imidazol-2yl)-2-hydroxy-5,6,7,8-tetrahydronaphthalen-1-yl]methanesulphonamide (A-61603) was found to be 10- and 54-fold more potent than norepinephrine and phenylephrine, respectively. Brimonidine (UK 14304) evoked significantly smaller contractile responses than norepinephrine and phenylephrine, showing the presence of a small population of a2-adrenoceptors in these arteries, and this was confirmed by the studies with selective a1- and a2-adrenoceptor antagonists prazosin and (8aR,12aS,13aS)-5,8,8a,9,10,11,12,12a,13a-decahydro-3-methoxyl-12-(ethylsulphonyl)-6H-isoquino[2,1-g][1,6]-naphthyridine (RS 79948). Prazosin, 5-methyl-urapidil, and 2-[2,6-dimethoxyphenoxyethyl]aminomethyl)-1,4-benzodioxane (WB 4101) shifted the potency of norepinephrine concentration dependently giving pA2 values of 9.4, 8.9, and 10.1, respectively, showing the presence of the a1A-subtype in these arteries. Pretreatment with 1 and 10 µM chloroethylclonidine did not affect the potency of and maximum responses to norepinephrine, ruling out the presence of the a1B-subtype in these arteries. 8-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-8-azaspiro[4.5]decane-7,9-dione (BMY 7378, 10 and 100 nM) did not affect the potency of norepinephrine but a small shift was observed by 1 µM BMY 7378, giving a pKB value of 7.1, much less than that reported for the a1D-subtype. These results suggest the predominant involvement of a1A-adrenoceptor in the contractile responses to norepinephrine in these arteries. The physiological role of this subtype in the maintenance of peripheral arterial resistance is yet to be confirmed.

Original languageEnglish
Pages (from-to)729-734
Number of pages6
JournalJournal of Pharmacology and Experimental Therapeutics
Volume299
Issue number2
Publication statusPublished - 1 Nov 2001

Fingerprint

Adrenergic Receptors
Norepinephrine
Arteries
Prazosin
Phenylephrine
A 61603
Naphthyridines
Groin
Subcutaneous Fat
Vascular Resistance
Skeletal Muscle
Maintenance
Population
BMY 7378

Keywords

  • human subcutaneous resistance arteries
  • a1-adrenoceptor subtypes

Cite this

Jarajapu, Y. P. R., Johnston, F., Berry, C., Renwick, A., McGrath, J. C., MacDonald, A., & Hillier, C. (2001). Functional characterization of a1-adrenoceptor subtypes in human subcutaneous resistance arteries. Journal of Pharmacology and Experimental Therapeutics, 299(2), 729-734.
Jarajapu, Yagna P.R. ; Johnston, Fiona ; Berry, Colin ; Renwick, Andrew ; McGrath, John C. ; MacDonald, Allan ; Hillier, Chris. / Functional characterization of a1-adrenoceptor subtypes in human subcutaneous resistance arteries. In: Journal of Pharmacology and Experimental Therapeutics. 2001 ; Vol. 299, No. 2. pp. 729-734.
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Jarajapu, YPR, Johnston, F, Berry, C, Renwick, A, McGrath, JC, MacDonald, A & Hillier, C 2001, 'Functional characterization of a1-adrenoceptor subtypes in human subcutaneous resistance arteries', Journal of Pharmacology and Experimental Therapeutics, vol. 299, no. 2, pp. 729-734.

Functional characterization of a1-adrenoceptor subtypes in human subcutaneous resistance arteries. / Jarajapu, Yagna P.R.; Johnston, Fiona; Berry, Colin; Renwick, Andrew; McGrath, John C.; MacDonald, Allan; Hillier, Chris.

In: Journal of Pharmacology and Experimental Therapeutics, Vol. 299, No. 2, 01.11.2001, p. 729-734.

Research output: Contribution to journalArticle

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T1 - Functional characterization of a1-adrenoceptor subtypes in human subcutaneous resistance arteries

AU - Jarajapu, Yagna P.R.

AU - Johnston, Fiona

AU - Berry, Colin

AU - Renwick, Andrew

AU - McGrath, John C.

AU - MacDonald, Allan

AU - Hillier, Chris

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N2 - The functional characteristics of the a1-adrenoceptor subtypes in human resistance arteries are still not clear. We recently reported that the a1A-adrenoceptor predominantly mediates contraction to norepinephrine in human skeletal muscle resistance arteries. In this study we extended these investigations to human subcutaneous resistance arteries. Arterial segments were isolated from the inguinal subcutaneous fat and mounted on a small vessel wire myograph. Potencies of agonists and antagonists were examined.N-[5-(4,5-dihydro-1H-imidazol-2yl)-2-hydroxy-5,6,7,8-tetrahydronaphthalen-1-yl]methanesulphonamide (A-61603) was found to be 10- and 54-fold more potent than norepinephrine and phenylephrine, respectively. Brimonidine (UK 14304) evoked significantly smaller contractile responses than norepinephrine and phenylephrine, showing the presence of a small population of a2-adrenoceptors in these arteries, and this was confirmed by the studies with selective a1- and a2-adrenoceptor antagonists prazosin and (8aR,12aS,13aS)-5,8,8a,9,10,11,12,12a,13a-decahydro-3-methoxyl-12-(ethylsulphonyl)-6H-isoquino[2,1-g][1,6]-naphthyridine (RS 79948). Prazosin, 5-methyl-urapidil, and 2-[2,6-dimethoxyphenoxyethyl]aminomethyl)-1,4-benzodioxane (WB 4101) shifted the potency of norepinephrine concentration dependently giving pA2 values of 9.4, 8.9, and 10.1, respectively, showing the presence of the a1A-subtype in these arteries. Pretreatment with 1 and 10 µM chloroethylclonidine did not affect the potency of and maximum responses to norepinephrine, ruling out the presence of the a1B-subtype in these arteries. 8-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-8-azaspiro[4.5]decane-7,9-dione (BMY 7378, 10 and 100 nM) did not affect the potency of norepinephrine but a small shift was observed by 1 µM BMY 7378, giving a pKB value of 7.1, much less than that reported for the a1D-subtype. These results suggest the predominant involvement of a1A-adrenoceptor in the contractile responses to norepinephrine in these arteries. The physiological role of this subtype in the maintenance of peripheral arterial resistance is yet to be confirmed.

AB - The functional characteristics of the a1-adrenoceptor subtypes in human resistance arteries are still not clear. We recently reported that the a1A-adrenoceptor predominantly mediates contraction to norepinephrine in human skeletal muscle resistance arteries. In this study we extended these investigations to human subcutaneous resistance arteries. Arterial segments were isolated from the inguinal subcutaneous fat and mounted on a small vessel wire myograph. Potencies of agonists and antagonists were examined.N-[5-(4,5-dihydro-1H-imidazol-2yl)-2-hydroxy-5,6,7,8-tetrahydronaphthalen-1-yl]methanesulphonamide (A-61603) was found to be 10- and 54-fold more potent than norepinephrine and phenylephrine, respectively. Brimonidine (UK 14304) evoked significantly smaller contractile responses than norepinephrine and phenylephrine, showing the presence of a small population of a2-adrenoceptors in these arteries, and this was confirmed by the studies with selective a1- and a2-adrenoceptor antagonists prazosin and (8aR,12aS,13aS)-5,8,8a,9,10,11,12,12a,13a-decahydro-3-methoxyl-12-(ethylsulphonyl)-6H-isoquino[2,1-g][1,6]-naphthyridine (RS 79948). Prazosin, 5-methyl-urapidil, and 2-[2,6-dimethoxyphenoxyethyl]aminomethyl)-1,4-benzodioxane (WB 4101) shifted the potency of norepinephrine concentration dependently giving pA2 values of 9.4, 8.9, and 10.1, respectively, showing the presence of the a1A-subtype in these arteries. Pretreatment with 1 and 10 µM chloroethylclonidine did not affect the potency of and maximum responses to norepinephrine, ruling out the presence of the a1B-subtype in these arteries. 8-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-8-azaspiro[4.5]decane-7,9-dione (BMY 7378, 10 and 100 nM) did not affect the potency of norepinephrine but a small shift was observed by 1 µM BMY 7378, giving a pKB value of 7.1, much less than that reported for the a1D-subtype. These results suggest the predominant involvement of a1A-adrenoceptor in the contractile responses to norepinephrine in these arteries. The physiological role of this subtype in the maintenance of peripheral arterial resistance is yet to be confirmed.

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Jarajapu YPR, Johnston F, Berry C, Renwick A, McGrath JC, MacDonald A et al. Functional characterization of a1-adrenoceptor subtypes in human subcutaneous resistance arteries. Journal of Pharmacology and Experimental Therapeutics. 2001 Nov 1;299(2):729-734.