Histamine levels during postexercise hypotension assessed by skeletal muscle microdialysis in inactive limbs

Abstract

The activation of histamine receptors in skeletal muscle has been implicated as a major mediator of postexercise hypotension. The purpose of this study was to examine the role that histamine plays in postexercise hypotension in humans. Histamine detection by microdialysis was tested by infusing compound 48–80 (a mast cell degranulator) through microdialysis probes inserted into the biceps muscle of resting humans. Interstitial histamine levels increased (P<0.05) from 2.46±.96 pre-infusion to 6.81±0.74 ng/ml post-infusion, confirming our ability to measure changes in endogenous histamine concentrations. Subsequently, six subjects had microdialysis probes inserted into their biceps muscle (inactive) 75 min prior to lower limb cycling exercise at 60% Vo2 peak for 60 min. Dialysate histamine concentrations were 2.22±0.21 before, 1.71±0.19 during, and 1.09±0.18 ng/ml after exercise and were not significantly different across time. These data indicate that muscle interstitial histamine levels do not increase during or following exercise in inactive limb muscles. Therefore, the next step will be to examine whether histamine levels are altered in the active limb muscles during the postexercise period by directly measuring histamine concentrations via microdialysis in the exercised muscle. Supported by AHA 0555623Z.