ROLE OF PROSTAGLANDINS IN HUMAN EXERCISE HYPEREMIA 1049

Abstract

The time course of change in mean blood velocity (MBV; pulsed Doppler), brachial artery diameter (D; echo Doppler), shear rate(γ=8*MBV/D), blood flow (Q), and mean perfusion pressure (MPP; finapres) were assessed to investigate the singular role that prostaglandins(PG) have on vascular dynamics during submaximal voluntary exercise in humans. 8 healthy men performed 5 min of supine dynamic handgrip exercise by alternately raising and lowering a weight (≈ 10% maximal voluntary contraction) with a work/rest cycle of 1s/1s. γ and ˙Q dynamics were altered by performing the exercise with the arm held 50° Above or Below the heart. Ibuprofen (IBU) (1200 mg/d), to reduce PG production, and placebo(PLAC), were administered orally for 2 d prior to two separate, and randomly assigned, testing sessions. Resting heart rate was reduced with IBU(52.2±2.6) compared with PLAC (56.6±2.9) (P<0.05) without change to MPP suggesting peripheral vasoconstriction had occurred. With IBU, end exercise MBV (31.6±1.7 cm/s) and D (4.7±0.1 mm) were modestly, but not significantly (P>0.05), altered compared with PLAC(35.0±2.7 cm/s, and 4.5±0.2 mm; MBV, and D respectively) but only in the Below tests after ≈ 15s of exercise. During Below tests, exercise γ was not different between IBU (52.8±3.4 s-1) and PLAC (52.7±5.7 s-1). Although it had been hypothesized that IBU would inhibit a PG-mediated vasodilation and reduce exercise hyperemia, the data indicate that either 1) IBU was not effective, 2) is of limited importance, or 3) that compensatory mechanisms allow a near normal response.