Effects of beta 1- vs. beta 1- beta 2-blockade on training adaptations in rat skeletal muscle.
The effect of selective vs. nonselective beta-blockade on fast-twitch [extensor digitorum longus (EDL)] and slow-twitch [soleus (SOL)] muscle enzyme activities following endurance training were characterized. Citrate synthase (CS), lactate dehydrogenase (LDH), and beta-hydroxyacyl-CoA dehydrogenase (HAD) activities were compared in SOL and EDL muscles of trained (T), metoprolol-trained (MT), propranolol-trained (PT), and sedentary (C) rats. Following 8 wk of treadmill running (1 h/day, 5 days/wk at approximately 30 m/min), LDH activity was depressed approximately 20% (P less than 0.05) in both SOL and EDL in only the PT rats, indicating inhibition of beta 2-mediated anaerobic glycolysis. EDL CS activity was similarly elevated in all three trained groups compared with sedentary controls. In SOL muscle, however, a drug attenuation effect was observed so that CS activity was increased only in the T (P less than 0.01) and MT (P less than 0.05) groups. HAD enzyme activity was increased somewhat (P less than 0.10) in SOL muscle in only the T group, but more so (P less than 0.05) in EDL in all three trained groups. The above findings suggest a training-induced selectivity effect not only with respect to beta 1-vs. beta 1-beta 2-blockers, but also with respect to muscle fiber type.
Thomas
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Jenkins
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D015094:3-Hydroxyacyl CoA Dehydrogenases / Q000378:metabolism; D000222:Adaptation, Physiological; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D002950:Citrate (si)-Synthase / Q000378:metabolism; D006339:Heart Rate / Q000187:drug effects; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008297:Male; D008790:Metoprolol / Q000494:pharmacology; D009132:Muscles / Q000187:drug effects / Q000201:enzymology / Q000502:physiology*; D010805:Physical Conditioning, Animal; D011433:Propranolol / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011943:Receptors, Adrenergic, beta / Q000187:drug effects / Q000502:physiology*
D000319:Adrenergic beta-Antagonists; D011943:Receptors, Adrenergic, beta; D011433:Propranolol; D015094:3-Hydroxyacyl CoA Dehydrogenases; D007770:L-Lactate Dehydrogenase; D002950:Citrate (si)-Synthase; D008790:Metoprolol