Physical training increases beta-adrenoceptor density and adenylate cyclase activity in high-oxidative skeletal muscle of diabetic rats.

The effects of physical training on beta-adrenergic-receptor density (Bmax) and adenylate cyclase (AC) activity in soleus muscles (type I) and the deep red portion (type IIa) and superficial white portion (type IIb) of vastus lateralis muscles in diabetic rats were investigated. Rats were rendered diabetic with streptozotocin ([STZ] 45 mg/kg intravenously [IV]) and were either kept sedentary ([SD] n = 12) or submitted to a progressive 10-week treadmill running program ([TD] n = 13). A group of normal sedentary rats served as controls ([SC] n = 13). Plasma glucose levels were increased in SD rats in comparison with SC rats (21.3 +/- 1.4 mmol/L v 7.7 +/- 0.2; mean +/- SE, P < .001), but levels were partially reversed to normal by training (10.7 +/- 1.7; P < .01 v SD). The gastrocnemius nicotinamide adenine dinucleotide (NAD)-isocitrate dehydrogenase (ICDH) activity was significantly increased in TD rats in comparison to SC or SD rats (P < .001). The Bmax and antagonist affinity (Kd) determined with 125iodocyanopindolol (ICYP) were not affected by diabetes in any of the three types of muscle. In type I muscle, TD rats showed a significant 67% increase in Bmax compared with that of SD rats (TD 26.7 +/- 2.0 v SD 16.0 +/- 1.0; P < .001). In type IIa muscle, Bmax was significantly higher by 68% in TD rats as compared with SD rats (TD 16.5 +/- 1.7 v SD 9.8 +/- 0.9 fmol/mg protein; P < .01).(ABSTRACT TRUNCATED AT 250 WORDS)