Prostaglandins contribute in an O2‐dependent manner to exercise hyperaemia following rhythmic and isometric handgrip exercise in young and older healthy subjects

Recreationally active young (Y;18‐25 yrs; n=12) and older (O; 60‐70 yrs; n=7) males performed rhythmic handgrip at 60% maximum voluntary contraction (MVC; 1 sec contraction/relaxation) for 3 min, and 30 min later, isometric handgrip at 60% MVC for 3 min or until exhaustion in a randomized cross over design. They breathed air or 40% O2, and Placebo (P) or cyclooxygenase inhibitor, Aspirin (Asp; 600 mg p.o.). In Y males, forearm vascular conductance (FVC) increased from 0.08±0.01 to 0.59±0.05 conductance units (CU) immediately after isometric contraction during P/air but to only 0.44±0.05*, 0.42±0.07* and 0.42±0.04* CU in P/O2, Asp/air and Asp/O2 respectively (*: P<0.05 vs P/air, Factorial ANOVA). Rhythmic contractions increased FVC from 0.06±0.01 to 0.54±0.08 in P/air and again to only 0.44±0.04*, 0.44±0.04* and 0.45±0.03* CU in P/O2, Asp/air and Asp/O2 respectively. Similarly, in O males, FVC increased from 0.09±0.03 to 0.66±0.09 CU during P/air immediately after isometric contraction and to only 0.50±0.05*, 0.45±0.07* and 0.51±0.05* CU in P/O2, Asp/air and Asp/O2 respectively. Rhythmic contractions increased FVC from 0.08±0.01 to 0.58±0.09 CU in P/air and to only 0.43±0.08*, 0.43±0.07* and 0.49±0.06* CU in P/O2, Asp/air and Asp/O2. Thus we propose that in young and older males, PGs contribute to hyperaemia following rhythmic and isometric contractions and that in both age groups, PG synthesis is O2‐dependent.