Contribution of prostaglandins to the dilation that follows isometric forearm contraction in human subjects: effects of aspirin and hyperoxia.
In 11 healthy volunteers, we evaluated, in a double-blind crossover study, whether the vasodilation that follows isometric contraction is mediated by prostaglandins (PGs) and/or is O2 dependent. Subjects performed isometric handgrip for 2 min at 60% maximal voluntary contraction (MVC), after pretreatment with placebo or aspirin (600 mg orally), when breathing air or 40% O2. Forearm blood flow was measured in the dominant forearm by venous occlusion plethysmography. Arterial blood pressure was also recorded, allowing calculation of forearm vascular conductance (FVC; forearm blood flow/arterial blood pressure). During air breathing, aspirin significantly reduced the increase in FVC that followed contraction at 60% MVC: from a baseline of 0.09 +/- 0.011 [mean +/- SE, conductance units (CU)], the peak value was reduced from 0.24 +/- 0.03 to 0.14 +/- 0.01 CU. Breathing 40% O2 similarly reduced the increase in FVC relative to that evoked when breathing air; the peak value was 0.24 +/- 0.03 vs. 0.15 +/- 0.02 CU. However, after aspirin, breathing 40% O2 had no further effect on the contraction-evoked increase in FVC (the peak value was 0.15 +/- 0.02 vs. 0.16 +/- 0.02 CU). Thus the present study indicates that prostaglandins make a substantial contribution to the peak of the vasodilation that follows isometric contraction of forearm muscles at 60% MVC. Given that hyperoxia similarly reduced the vasodilation and attenuated the effect of aspirin, we propose that the stimulus for prostaglandin synthesis and release is hypoxia of the endothelium.
Win
Thet Su
TS
Dept. of Physiology, Division of Medical Sciences, The Medical School, Birmingham B15 2TT, UK.
Marshall
Janice M
JM
D000328:Adult; D001241:Aspirin / Q000008:administration & dosage*; D001783:Blood Flow Velocity / Q000187:drug effects; D018592:Cross-Over Studies; D004311:Double-Blind Method; D005542:Forearm / Q000098:blood supply / Q000503:physiopathology; D018737:Hand Strength; D006801:Humans; D018496:Hyperoxia / Q000503:physiopathology*; D009119:Muscle Contraction / Q000187:drug effects*; D018482:Muscle, Skeletal / Q000098:blood supply* / Q000187:drug effects / Q000503:physiopathology*; D010100:Oxygen / Q000378:metabolism*; D011453:Prostaglandins / Q000378:metabolism*; D014655:Vascular Resistance / Q000187:drug effects; D014664:Vasodilation / Q000187:drug effects*
D011453:Prostaglandins; D001241:Aspirin; D010100:Oxygen