Key result
Human subcutaneous resistance arteries, but not medium-sized muscular arteries, showed concentration-dependent vasoconstriction responses to the alpha 2-agonist B-HT 933.
Postjunctional alpha 2-adrenoceptors mediate vasoconstriction in human subcutaneous resistance arteries but not in medium-sized muscular arteries.
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Supports vessel-specific α2-adrenoceptor vasoconstriction; hypothesis-generating and requires in vivo confirmation before clinical consideration.
In vitro studies have been performed on human medium-sized muscular arteries (internal diameter 1-4 mm) in a classical organ bath and with human subcutaneous resistance arteries (internal diameter 103-626 microns) in a microvascular myograph. 2. Although the medium-sized muscular arteries showed no response to either of the alpha 2-agonists B-HT 933 or UK 14304 in concentrations up to 10 microM, the subcutaneous resistance arteries from all regions examined showed well-pronounced and concentration-dependent responses to B-HT 933, the pD2 (-log EC50) being 5.11 +/- 0.09. 3. In the resistance arteries the alpha 2-antagonist yohimbine caused a parallel shift to the right of the B-HT 933 concentration-response curve; the yohimbine pA2 for the B-HT 933 receptor was 7.86 +/- 0.12. 4. There was an inverse relationship between the maximum response to B-HT 933 and the calibre of the resistance vessels. 5. These results indicate the presence of a postjunctional alpha 2-adrenoceptor in human subcutaneous resistance arteries and not in medium sized muscular arteries.
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Nielsen et al. (1989) studied this question. alpha 2-agonists (B-HT 933 or UK 14304) was evaluated on Vasoconstriction response (pD2). Human subcutaneous resistance arteries, but not medium-sized muscular arteries, showed concentration-dependent vasoconstriction responses to the alpha 2-agonist B-HT 933.
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