title: Physiological mechanisms contributing to increased interleukin-1 secretion.
abstract: Interleukin-1 (IL-1) is a monocyte-derived polypeptide that mediates many host defense adaptations to environmental and infectious stresses. This investigation was intended to characterize further IL-1 activity found in human plasma following exercise (3) and to identify physiological initiators of IL-1 secretion. IL-1 activity was measured by the ability of plasma fractions to stimulate lymphocyte proliferation. This activity appeared in plasma several hours after exercise on a cycle ergometer (1 h at 60% of aerobic capacity, n = 8 subjects) and was neutralized with a specific antiserum to human IL-1. The hypothesis that IL-1 release from monocytes was initiated by phagocytosis of material from cells damaged by exercise was tested. The increase in IL-1 activity did not correlate significantly (r = 0.55) with creatine kinase activity, a marker for release of intracellular proteins into the circulation, and IL-1 secretion by monocytes was not stimulated by incubation with red blood cell lysates in vitro. Thus the stimulus for IL-1 secretion did not appear to be related to a scavenging function of monocytes. The possibility that IL-1 secretion may be mediated by stress hormones associated with exercise was examined. IL-1 secretion by monocytes was increased up to 48 +/- 18% (P less than 0.01) by addition of physiological concentrations of epinephrine in vitro. Low concentrations of hydrocortisone (1 ng/ml) also augmented IL-1 secretion by 58 +/- 20%. Higher concentrations in the physiological range had no effect, and combinations of epinephrine and hydrocortisone suppressed IL-1 secretion.(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D000328:Adult; D002478:Cells, Cultured; D005591:Chemical Fractionation; D003402:Creatine Kinase / Q000097:blood; D004837:Epinephrine / Q000494:pharmacology; D006801:Humans; D006854:Hydrocortisone / Q000494:pharmacology; D007375:Interleukin-1 / Q000502:physiology*; D009000:Monocytes / Q000187:drug effects / Q000378:metabolism; D010587:Phagocytosis; D005082:Physical Exertion
chemical_list: D007375:Interleukin-1; D003402:Creatine Kinase; D006854:Hydrocortisone; D004837:Epinephrine