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The John B. Pierce Laboratory and 1 Departments of Cellular & Molecular Physiology
2 Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT 06519, USA
Physical diminishes with ageing, but little is known of how the microvascular supply to skeletal muscle fibres is affected. To test the hypothesis that ageing alters blood flow control, we investigated network architecture and vasomotor responses of arterioles in the gluteus maximus muscle of young (2–3 months), adult (12–14 months) and old (18–20 months) C57BL6 male mice (n = 83) (Young, Adult and Old, respectively). Microvascular casts revealed that the total number, length and surface area of arteriolar segments (diameter, 10–50 µm) were not significantly different across age-groups. However, for arterioles with diameter of 30 µm, tortuosity and branch angles increased with age (P < 0.05). In anaesthetized mice, second-order (2A) distributing arterioles had similar resting (17 ± 1 µm) and maximal (37 ± 1 µm) diameters and similar responsiveness to cumulative (10–10–10–4 M) superfusion of acetylcholine or phenylephrine. With superfusate oxygen level raised from 0 to 21%, 2A arteriolar constriction in Young (11 ± 1 µm) was greater (P < 0.05) than Adult and Old (5 ± 1 µm). Observed 1 mm upstream from microiontophoresis of ACh (1 µA, 1 s), conducted vasodilatation was 10 ± 1 µm in Young, 17 ± 1 µm in Adult and 6 ± 1 µm in Old (P < 0.05). With muscle contractions (2, 4 and 8 Hz; 30 s) arteriolar diameter increased similarly across age-groups (6 ± 1, 11 ± 1 and 18 ± 1 µm, respectively). Muscle mass and active tension were similar across age-groups yet postcontraction vasodilatation recovered more rapidly in Old versus Adult and Young (P < 0.05). With arteriolar network architecture maintained during ageing, the impairment in conducted vasodilatation and attenuation of postcontraction vasodilatation may compromise exercise tolerance.
(Received 17 May 2004;
accepted after revision 14 September 2004;
first published online 16 September 2004)
Corresponding author S. S. Segal: The John B. Pierce Laboratory, Yale University School of Medicine, 290 Congress Ave, New Haven, CT 06519, USA. Email: sssegal{at}jbpierce.org
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