Effects of lipopolysaccharide‐induced systemic inflammation on the contractile properties of the fast twitch extensor digitorum longus muscle in mice (1102.19)

Abstract

Chronic sepsis, which includes a large inflammatory response, leads to muscle wasting, decreased muscle contractile forces and an increase in fatigability (Lanone, et al., 2005; Rossignol, et al., 2008). The effects of lower levels of systemic inflammation on muscle contractile properties have not been well studied. We tested the hypothesis that contractile properties of skeletal muscles are altered by lower levels of systemic inflammation using an in vitro adult mouse extensor digitorum longus muscle preparation. We tested the response to inflammation caused by a high dose of lipopolysaccharide (LPS; 7.5 x 10^5 Endotoxin Units/ kg IP 18 hrs before sacrifice; n=6) with or without a 1 month exposure to low LPS (7.5 x 104 EU/kg; 2/wk, n=4). Controls were given a saline injection 18 hrs before sacrifice (n=6). Twitch and tetanic contractions were induced by bath electrodes and a 10 min fatigue test (.5 ms pulse width, 60 Hz, 350 ms train at supramaximal voltage every 3 s) was performed. Muscle contractile properties including time to peak contraction, half‐relaxation time and fatigue index (40th train tension/maximal tetanic tension) were not significantly different from control values following high LPS, even when it was preceded by a month of low LPS. Future studies will increase the sample size and confirm that LPS‐induced systemic inflammation at our doses does not alter contractile properties. Grant Funding Source: Supported by a CSUPERB President's Commission Fellowship (RGM) and a CSUPERB New Investigator (KAW)