[Effects of nifedipine on myosin heavy chain (MHC) isoforms transition in unloaded soleus].
OBJECTIVE
To observe the effects of nifedipine, a blocker of L-type Ca2+ channel, on soleus weight and expression of myosin heavy chain (MHC) isoforms in control and tail-suspended rats.


METHODS
Animals were treated with nifedipine at a dose of 10 mg/kg per day in drinking water for 1 or 2 weeks. The expression of MHC isoform protein was observed by SDS-polyacrylamide gel electrophoresis at 4 degrees C. The expression of MHC mRNA was detected by RT-PCR.


RESULTS
The relative weight (muscle weight/body weight) of soleus muscle was decreased by 39.5% and 51.7% in 1 and 2 weeks of tail-suspended group respectively, but no changes in extensor digitorum longus (EDL) weight was found. The relative weight of soleus and EDL in 1 or 2 weeks of nifedipine treated control group showed no changes as compared with the untreated control group. The relative weight of soleus in 1 or 2 weeks of nifedipine treated tail-suspension group decreased by 36.6% or 52.0%, respectively, as compared with control, but there was no difference between tail-suspension group with or without nifedipine treatment. The expression of MHC I, IIa mRNA and protein could be detected in control soleus with or without nifedipine treatment. The expression MHC I, IIa, IIx and IIb mRNA was detected in 1 or 2 weeks of unloaded soleus with or without nifedipine treatment. Nifedipine inhibited the expression of II type MHC mRNA in unloaded soleus and expression of MHC IIa protein in control and unloaded soleus.


CONCLUSIONS
Nifedipine can not resist atrophy of unloaded soleus, but inhibit the transition of MHC from slow to fast isoforms at the transcription level.
Han-zhong
HZ
Feng
Zhi-bin
ZB
Yu
D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D019417:Hindlimb Suspension; D009124:Muscle Proteins / Q000378:metabolism; D018482:Muscle, Skeletal / Q000378:metabolism*; D018995:Myosin Heavy Chains / Q000187:drug effects*; D009543:Nifedipine / Q000494:pharmacology*; D009929:Organ Size; D020033:Protein Isoforms / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D018474:Weightlessness Simulation
D002121:Calcium Channel Blockers; D009124:Muscle Proteins; D020033:Protein Isoforms; D012333:RNA, Messenger; D018995:Myosin Heavy Chains; D009543:Nifedipine