Endogenous Pyrogen Activity in Human Plasma After Exercise.

Abstract

Endogenous pyrogen (EP) is a protein released by phagocytic leukocytes in response to infection which mediates many non-specific host defense mechanisms. Evidence obtained with a rat bioassay for EP suggests that this protein is also released as a result of endurance exercise. Rats respond to intraperitoneal injection of human EP produced in vitro and plasma from infected human subjects with a dose dependent monophasic elevation of rectal temperature. In addition, rat plasma iron and zinc concentrations fall in response to injection of plasma containing EP. Plasma obtained from human subjects after one hour of exercise on a cycle ergometer at 60% of maximum aerobic capacity and injected into rats caused elevation of rat rectal temperature and depression of rat plasma iron and zinc concentrations. The pyrogenic component was denatured by heating to 65(DEGREES)C for 90 minutes and had an apparent molecular weight of 14,000 daltons. Mononuclear leukocytes obtained after exercise and incubated in vitro released a factor into the media which also elevated rat rectal temperature and reduced rat trace metal concentrations. These results suggest that exercise stimulates the release of endogenous pyrogen.