Rapid vasodilation in response to passive leg movement with age: the role of nitric oxide and the impact of perfusion pressure (546.6)

Abstract

We sought to elucidate the contribution of NO, with and without posture‐induced increases in femoral perfusion pressure (FPP), on the rapid (first 7 sec) vasodilatory response to passive leg movement (PLM) with age. PLM was performed in 8 young (24±1 yrs) and 7 old (75±3 yrs) healthy males, with (blk) and without (ctrl) NO synthase (NOS) inhibition, in both the supine and upright‐seated posture. Peripheral hemodynamic responses were determined with Doppler ultrasound. In the supine posture, NOS inhibition had no effect on the rapid vasodilation (leg vascular conductance slope/time) in either the young (ctrl: 0.78 ± 0.10; blk: 0.71 ± 0.16 ml/min/mmHg/sec; p>0.05) or on the already attenuated response in the old (ctrl: 0.25 ± 0.06; blk: 0.33 ± 0.07 ml/min/mmHg/sec; p>0.05). However, in the upright‐seated posture, which similarly increased FPP in both groups (~7mmHg), NOS inhibition significantly attenuated the posture‐induced augmentation of rapid vasodilation in the young (ctrl: 1.25 ± 0.23; blk: 0.74 ± 0.11 ml/min/mmHg/sec; p<0.05), with no effect in the old (ctrl: 0.38 ± 0.05; blk: 0.26 ± 0.05 ml/min/mmHg/sec; p>0.05). PLM‐induced rapid vasodilation in the supine posture is NO‐independent and this response is attenuated with age. In the young, elevated FPP increases the role of NO in this rapid vasodilatory response, but has no effect in the old, likely due to decreased NO bioavailability in this population.Grant Funding Source: VA Merit Grant E6910R and PPG Grant