title: Contribution of prostaglandins to the dilation that follows isometric forearm contraction in human subjects: effects of aspirin and hyperoxia.
abstract: 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.
authors.affiliation: Dept. of Physiology, Division of Medical Sciences, The Medical School, Birmingham B15 2TT, UK.
authors.forename: Thet Su
authors.initials: TS
authors.lastname: Win
authors.forename: Janice M
authors.initials: JM
authors.lastname: Marshall
mesh_terms: 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*
chemical_list: D011453:Prostaglandins; D001241:Aspirin; D010100:Oxygen