Effects of leukemia inhibitory factor on rat skeletal muscles are modulated by clenbuterol.

Leukemia inhibitory factor (LIF) is implicated in skeletal muscle regeneration, but the effect of exogenous LIF on uninjured muscles is not known. We tested the hypothesis that LIF administration would stimulate muscle hypertrophy, with an increased effect during clenbuterol-induced fiber remodeling. Rats received daily injections of either saline or LIF, and either regular or clenbuterol-supplemented drinking water for 4 weeks. In the slow-twitch soleus muscles of LIF-treated rats, specific force (sP(o)) and muscle fiber size were increased by approximately 13% and approximately 26%, respectively, compared to saline-treated rats. In the soleus muscles of rats receiving LIF and clenbuterol, compared to rats receiving clenbuterol alone, maximum isometric tension (P(o)) was approximately 19% greater. LIF alone did not affect the properties of fast-twitch extensor digitorum longus (EDL) muscles, but in rats receiving LIF and clenbuterol, compared to clenbuterol alone, EDL fiber size and muscle mass were increased by approximately 20% and approximately 10%, respectively. The hypertrophic effects of exogenous LIF on uninjured skeletal muscles indicate that LIF may have application in the treatment of conditions characterized by muscle wasting. Copyright 2002 John Wiley & Sons, Inc.