Activin A release into the circulation is an early event in systemic inflammation and precedes the release of follistatin

Recent evidence suggests a role for activin A, and its binding protein, fol listatin, in inflammatory pathways. However, whether activin is released sy stemically during inflammation is not known. In this study, a release of ac tivin A into the circulation occurred in sheep within 1 hour of injection o f lipopolysaccharide. This rapid peak in activin A preceded the release of the key inflammatory cytokines, tumor necrosis factor-alpha and interleukin -6. Follistatin release into the circulation occurred some 4 hours after th e peak of activin A and continued out to 24 hours from lipopolysaccharide t reatment. These data are the first to document a circulatory response of ac tivin A to an inflammatory stimulus, and together with previous findings, s uggest that activin A may have both pro- and antiinflammatory actions in re gulating cytokine-driven pathways.