Endurance training, not acute exercise, differentially alters beta-receptors and cyclase in skeletal fiber types.
beta-Adrenergic receptor binding characteristics and adenylate cyclase activity were examined in rat skeletal muscle membranes to determine if acute exercise or endurance training altered beta-receptors or adenylate cyclase activity in different muscle fiber types. Binding characteristics and adenylate cyclase activity were examined in type IIA [red fast-twitch, red vastus (RV)], type IIB [white fast-twitch, white vastus (WV)], and type I [red slow-twitch, soleus (S)] muscles. Acute exercise involved a 20-min run on a treadmill at 20 m/min and did not alter beta-receptor density or adenylate cyclase activity in any of the fiber types examined. Endurance training consisted of a progressive treadmill protocol that involved increasing intensity and duration of exercise for 18 wk. beta-Adrenergic receptor density increased in skeletal muscle fiber types primarily recruited during submaximal training (types I and IIA), whereas nonreceptor-mediated adenylate cyclase activity was altered in the three fiber types. Endurance training significantly increased beta-receptor density in RV by 25% and in S by 19% (P less than 0.05), whereas in WV beta-receptor density was not altered. Basal adenylate cyclase activity in RV was increased approximately 2.5 fold by endurance training. Nonreceptor-mediated adenylate cyclase activity, stimulated by NaF and forskolin, increased by approximately twofold in both RV and WV as a result of endurance training. The data support and extend previous observations to show greater effects of endurance training in types I and IIA fibers with respect to alterations in beta-receptor density and alterations in adenylate cyclase activity in each fiber type. Acute exercise did not alter these parameters either in trained or untrained rats.
Buckenmeyer
P J
PJ
Department of Physical Education, University of Maryland, College Park 20742.
Goldfarb
A H
AH
Partilla
J S
JS
Piñeyro
M A
MA
Dax
E M
EM
D000262:Adenylyl Cyclases / Q000378:metabolism*; D000818:Animals; D005576:Colforsin / Q000494:pharmacology; D006160:Guanosine Triphosphate / Q000494:pharmacology; D006165:Guanylyl Imidodiphosphate / Q000494:pharmacology; D007545:Isoproterenol / Q000494:pharmacology; D007700:Kinetics; D008297:Male; D009132:Muscles / Q000201:enzymology / Q000378:metabolism*; D009928:Organ Specificity; D010805:Physical Conditioning, Animal; D005082:Physical Exertion; D010869:Pindolol / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D011943:Receptors, Adrenergic, beta / Q000378:metabolism*; D012016:Reference Values; D012969:Sodium Fluoride / Q000494:pharmacology; D013384:Succinate Cytochrome c Oxidoreductase / Q000378:metabolism
D011943:Receptors, Adrenergic, beta; D005576:Colforsin; D006165:Guanylyl Imidodiphosphate; D006160:Guanosine Triphosphate; D012969:Sodium Fluoride; D010869:Pindolol; D013384:Succinate Cytochrome c Oxidoreductase; D000262:Adenylyl Cyclases; D007545:Isoproterenol