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ARS Home » Northeast Area » Boston, Massachusetts » Jean Mayer Human Nutrition Research Center On Aging » Research » Publications at this Location » Publication #37494
Title: AGING AND STRESS-INDUCED CHANGES IN COMPLEMENT ACTIVATION AND NEUTROPHIL MOBILIZATION

Author
item CANNON JOSEPH G - PENN STATE
item FIATARONE MARIA - TUFTS-HNRCA
item FIELDING ROGER A - TUFTS-HNRCA
item EVANS WILLIAM J - PENN STATE

Submitted to: Journal of Applied Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/11/1994
Publication Date: N/A
Citation: N/A

Interpretive Summary: Eccentric exercise such as walking downstairs or running downhill is a component of daily activity. This type of exertion involves forced lengthening of a muscle as it develops tension. Prolonged performance of an activity comprised primarily of eccentric muscle actions results in immediate disruption in muscle fibers visible in muscle biopsies. Delayed onset of muscle soreness, elevated protein concentrations in blood circulation, and increased urinary excretion of protein breakdown products are also indicators of prolonged excentric exercise. In a previous study, we found that young adults under 30 years of age responded to eccentric exercise with significantly greater increases in circulating neutrophils (white blood cells that fight infection) and plasma creatine kinase (CK) activity, a product of muscle breakdown, than older adults under 55 years of age, who exercised at the same relative intensity based on heart rate. The present investigation has sought to determine whether these inflammatory responses are related to each other or to increases in plasma creatine kinase activity after eccentric exercise. In addition, this investigation sought to confirm the age-related differences in the neutrophil and CK responses to eccentric exercise observed previously and to determine whether a similar age-related decline in bodily response to muscle inflammation occurs.

Technical Abstract: We measured the extent of complement activation and neutrophil mobil- ization after eccentric exercise to determine whether these responses were age dependent and whether they were associated with changes in plasma creatine kinase (CK), a marker for muscle membrane integrity. Repeated forced lengthening of a muscle as it develops tension causes immediate ultrastructural damage to sarcomeres, followed by delayed-onset muscle soreness and release of myocellular enzymes. This can be accomplished in quadriceps muscles by running downhill or by resisting bicycle pedals driven backward by a motor. Twelve older (61-72 yr) and 9 younger (20- 32 yr) subjects performed one of these activities for 45 min at an inten- sity of 78 +/- 2% of maximum heart rate. For all subjects, a median increase of 21% in plasma des-Arg-C3a levels occurred immediately after the protocol, circulating neutrophils increased 66 +/- 10% by 4-6 h, and plasma CK increased 135 +/- 25% by 24 h. The peak increases in neutrophils correlated with the peak increases in des-Arg-C3a (rho = 0.662, P = 0.006), and the peak increases in CK correlated with the rise in neutrophils (rho = 0.523, P = 0.027). The increases in neutrophils and plasma CK were significantly smaller in the older subjects (P <0.05). The results indicate that increased concentrations of circulating CK after muscle injury are associated with a sequential cascade of inflammatory mediators. Furthermore, neutrophil mobilization, but not complement activation, was diminished in older subjects in response to this stress.