Effects of the beta2-agonist clenbuterol on beta1- and beta2-adrenoceptor mRNA expressions of rat skeletal and left ventricle muscles.
The beta2-agonist clenbuterol [4-amino-alpha(t-butyl-amino)methyl-3,5-dichlorobenzyl alcohol] is used as a non-steroidal anabolic drug for sports doping. The effects of clenbuterol on the transcriptional process and mRNA stability of beta-adrenoceptor (beta-AR) in skeletal and cardiac muscles are still unknown. Therefore, we investigated the effects of clenbuterol on beta1- and beta2-AR mRNA expressions of fast-twitch fiber-rich extensor digitorum longus (EDL), slow-twitch fiber-rich soleus (SOL), and left ventricle (LV) muscles by real-time RT-PCR. Adult male Sprague Dawley rats were divided into the clenbuterol-administered group and control group. The administration (dose = 1.0 mg/kg body weight/day, s.c.) of clenbuterol was maintained for 10 days. The administration of clenbuterol significantly increased the weight, RNA concentration, and total RNA content of EDL muscle. No effects of clenbuterol on those of SOL and LV muscles, however, were observed. The administration of clenbuterol significantly decreased beta1-AR mRNA expression of LV muscle. Furthermore, the administration of clenbuterol significantly decreased beta2-AR mRNA expression of EDL and LV muscles. No effect of clenbuterol on beta2-AR mRNA expression of SOL muscle, however, was observed. These results suggest that the effects of clenbuterol on beta1- and beta2-AR mRNA expressions and muscle hypertrophy depend on muscle fiber types.
Sato
Shogo
S
Laboratory of Physiological Sciences, Faculty of Human Sciences, Waseda University, Tokorozawa, Saitama, Japan.
Nomura
Sachiko
S
Kawano
Fuuun
F
Tanihata
Jun
J
Tachiyashiki
Kaoru
K
Imaizumi
Kazuhiko
K
D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D000818:Animals; D002976:Clenbuterol / Q000494:pharmacology*; D005786:Gene Expression Regulation / Q000187:drug effects*; D006352:Heart Ventricles / Q000187:drug effects / Q000378:metabolism; D006984:Hypertrophy / Q000209:etiology; D008297:Male; D018482:Muscle, Skeletal / Q000187:drug effects / Q000378:metabolism; D012333:RNA, Messenger / Q000187:drug effects* / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D018342:Receptors, Adrenergic, beta-1 / Q000187:drug effects / Q000378:metabolism; D018343:Receptors, Adrenergic, beta-2 / Q000187:drug effects / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014158:Transcription, Genetic / Q000187:drug effects
D000318:Adrenergic beta-Agonists; D012333:RNA, Messenger; D018342:Receptors, Adrenergic, beta-1; D018343:Receptors, Adrenergic, beta-2; D002976:Clenbuterol