WISE 2005: responses of women to sublingual nitroglycerin before and after 56 days of 6° head-down bed rest.
This study tested the hypothesis that cardiovascular effects of sublingual nitroglycerin (NG) would be exaggerated after 56 days of 6° head-down bed rest (HDBR) in women, and that an aerobic and resistive exercise countermeasure (EX, n = 8) would reduce the effect compared with HDBR without exercise (CON, n = 7). Middle cerebral artery maximal blood flow velocity (CBFV), cardiac stroke volume (SV), and superficial femoral artery blood flow (Doppler ultrasound) were recorded at baseline rest and for 5 min following 0.3 mg sublingual NG. Post-HDBR, NG caused greater increases in heart rate (HR) in CON compared with EX (+24.9 ± 7.7 and +18.8 ± 6.6 beats/min, respectively, P < 0.0001). The increase in HR combined with reductions in SV to maintain cardiac output. Systolic, mean, and pulse pressures were reduced 5-10 mmHg by NG, but total peripheral resistance was only slightly reduced at 3 min after NG. Reductions in CBFV of -12.5 ± 3.8 cm/s were seen after NG, but a reduction in the Doppler resistance index suggested dilation of the middle cerebral artery with no differences after HDBR. The femoral artery dilated with NG and blood flow was reduced ∼50% with the appearance of large negative waves suggesting a marked increase in downstream resistance, but there were no effects of HDBR. In general, responses of women to NG were not altered by HDBR; the greater increase in HR in CON but not EX was probably a consequence of cardiovascular deconditioning. These results contrast with the hypothesis and a previous investigation of men after HDBR by revealing no change in cardiovascular responses to exogenous nitric oxide.
Faculty of Applied Health Sciences, University of Waterloo, Waterloo, Ontario, Canada.
K A
KA
Zuj
H
H
Edgell
J K
JK
Shoemaker
M A
MA
Custaud
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P
Arbeille
R L
RL
Hughson
D000286:Administration, Sublingual; D000328:Adult; D001510:Bed Rest; D001783:Blood Flow Velocity / Q000187:drug effects*; D001794:Blood Pressure / Q000187:drug effects; D018493:Cardiovascular Deconditioning / Q000187:drug effects; D005260:Female; D005263:Femoral Artery / Q000000981:diagnostic imaging / Q000187:drug effects; D018475:Head-Down Tilt / Q000502:physiology; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D020768:Middle Cerebral Artery / Q000000981:diagnostic imaging / Q000187:drug effects; D005996:Nitroglycerin / Q000008:administration & dosage*; D010101:Oxygen Consumption / Q000187:drug effects; D055070:Resistance Training; D013318:Stroke Volume / Q000187:drug effects*; D018608:Ultrasonography, Doppler; D014655:Vascular Resistance / Q000187:drug effects; D014665:Vasodilator Agents / Q000008:administration & dosage*; D018544:Weightlessness Countermeasures
D014665:Vasodilator Agents; D005996:Nitroglycerin