TY - JOUR
T1 - Salbutamol enhances isotonic contractile properties of rat diaphragm muscle
AU - Van Der Heijden, H. F.M.
AU - Zhan, W. Z.
AU - Prakash, Y. S.
AU - Dekhuijzen, P. N.R.
AU - Sieck, G. C.
PY - 1998/8
Y1 - 1998/8
N2 - The effects of the β2-adrenoceptor agonist salbutamol (Slb) on isometric and isotonic contractile properties of the rat diaphragm muscle (Dia(mus)) were examined. A loading dose of 25 μg/kg Slb was administered intracardially before Dia(mus) excision to ensure adequate diffusion. Studies were then performed with 0.05 μM Slb in the in vitro tissue chamber. cAMP levels were determined by radioimmunoassay. Compared with controls (Ctl), cAMP levels were elevated after Slb treatment. In Slb-treated rats, isometric twitch and maximum tetanic force were increased by ~40 and ~20%, respectively. Maximum shortening velocity increased by ~15% after Slb treatment, and maximum power output increased by ~25%. During repeated isotonic activation, the rate of fatigue was faster in the Slb-treated Dia(mus), but both Slb-treated and Ctl Dia(mus) fatigued to the same maximum power output. Still, endurance time during repetitive isotonic contractions was ~10% shorter in the Slb-treated Dia(mus). These results are consistent with the hypothesis that β-adrenoceptor stimulation by Slb enhances Dia(mus) contractility and that these effects of Slb are likely mediated, at least in part, by elevated cAMP.
AB - The effects of the β2-adrenoceptor agonist salbutamol (Slb) on isometric and isotonic contractile properties of the rat diaphragm muscle (Dia(mus)) were examined. A loading dose of 25 μg/kg Slb was administered intracardially before Dia(mus) excision to ensure adequate diffusion. Studies were then performed with 0.05 μM Slb in the in vitro tissue chamber. cAMP levels were determined by radioimmunoassay. Compared with controls (Ctl), cAMP levels were elevated after Slb treatment. In Slb-treated rats, isometric twitch and maximum tetanic force were increased by ~40 and ~20%, respectively. Maximum shortening velocity increased by ~15% after Slb treatment, and maximum power output increased by ~25%. During repeated isotonic activation, the rate of fatigue was faster in the Slb-treated Dia(mus), but both Slb-treated and Ctl Dia(mus) fatigued to the same maximum power output. Still, endurance time during repetitive isotonic contractions was ~10% shorter in the Slb-treated Dia(mus). These results are consistent with the hypothesis that β-adrenoceptor stimulation by Slb enhances Dia(mus) contractility and that these effects of Slb are likely mediated, at least in part, by elevated cAMP.
KW - Fatigue
KW - Skeletal muscle
KW - Velocity of shortening
KW - cAMP
KW - β-adrenoceptor agonist
UR - http://www.scopus.com/inward/record.url?scp=0031904849&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0031904849&partnerID=8YFLogxK
U2 - 10.1152/jappl.1998.85.2.525
DO - 10.1152/jappl.1998.85.2.525
M3 - Article
C2 - 9688729
AN - SCOPUS:0031904849
SN - 8750-7587
VL - 85
SP - 525
EP - 529
JO - Journal of applied physiology
JF - Journal of applied physiology
IS - 2
ER -