Reductions in basal limb blood flow and vascular conductance with human ageing: role for augmented alpha-adrenergic vasoconstriction.
J Physiol
; 536(Pt 3): 977-83, 2001 Nov 01.
Article
em En
| MEDLINE
| ID: mdl-11691889
ABSTRACT
1. Basal whole-limb blood flow and vascular conductance decrease with age in men. We determined whether these age-associated changes in limb haemodynamics are mediated by tonically augmented sympathetic alpha-adrenergic vasoconstriction. 2. Seven young (28 +/- 2 years; mean +/- S.E.M.) and eight older (64 +/- 2 years) healthy, normotensive adult men were studied. Baseline femoral artery blood flow (Doppler ultrasound) and calculated vascular conductance were 29 and 31 % lower, respectively, and vascular resistance was 53 % higher in the older men (all P < 0.001). 3. Local (intra-femoral artery) alpha-adrenergic receptor blockade with phentolamine evoked greater increases in femoral blood flow (105 +/- 11 vs. 60 +/- 6 %) and vascular conductance (125 +/- 13 vs. 66 +/- 7 %), and reductions in vascular resistance (55 +/- 2 vs. 39 +/- 3 %) in the experimental limb of the older compared with the young men (all P < 0.001). As a result, alpha-adrenergic receptor blockade eliminated the significance of the age-associated differences in absolute levels of femoral blood flow (500 +/- 51 vs. 551 +/- 35 ml min(-1)), vascular conductance (6.02 +/- 0.73 vs. 6.33 +/- 0.26 U), and vascular resistance (0.17 +/- 0.03 vs. 0.16 +/- 0.01 U; P = 0.4-0.8, n.s.). Femoral haemodynamics in the control limb were unaffected by phentolamine administration in the contralateral (experimental) limb. Complete alpha-adrenergic receptor blockade was demonstrated by the absence of vasoconstriction in the experimental limb in response to the cold pressor test. Local propranolol was administered to control for any beta-adrenergic effects of phentolamine. Propranolol did not affect haemodynamics in the experimental or control limbs. 4. Our results indicate that the age-related reductions in basal limb blood flow and vascular conductance are mediated largely by chronically elevated sympathetic alpha-adrenergic vasoconstriction. This may have important physiological and pathophysiological implications for the ageing human.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Resistência Vascular
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Vasoconstrição
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Envelhecimento
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Receptores Adrenérgicos alfa
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Extremidades
Limite:
Adult
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Aged
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Humans
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Male
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Middle aged
Idioma:
En
Revista:
J Physiol
Ano de publicação:
2001
Tipo de documento:
Article
País de afiliação:
Estados Unidos