ISSN:
1435-1803
Keywords:
streptozotocin
;
diabetic rats
;
exercise-training
;
beta-adrenergic receptors
;
plasma catecholamines
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Summary The effects of physical training on beta-adrenergic receptors were evaluated in heart ventricular tissue of diabetic rats. Mild diabetes mellitus was induced in rats with streptozotocin (45 mg/kg, iv). They were then submitted to a progressive 10-week running programme on a treadmill. Binding studies were done at six different concentrations of (−) [3H] dihydroalprenolol (0.5 to 14.4 nM) with ventricular membrane preparations from control (n=13), sedentary diabetic (n=9) and trained diabetic rats (n=10). Direct linear plot analysis of the data revealed that the total number of beta-adrenoceptors was reduced in sedentary diabetic rats as compared to control (2231±207 vs 2922±211 fmol/ventricules; P〈0.05); however, there was no significant change in the receptor density expressed as fmol/mg of membrane protein (40±3 vs 43±3; P〉0.05). On the other hand, the beta-adrenergic binding sites were decreased in trained diabetic rats, either expressed as the total number of receptors (1920±179 vs 2922±211; P〈0.01), or as fmol/mg of membrane protein (30±3 vs 43±3; P〈0.01). There was no significant change in the dissociation constant (KD) of these receptors between groups (KD=4.08±0.51, 4.69±0.93 and 2.88±0.39 nM respectively for control, sedentary diabetic and diabetic trained animals). The basal epinephrine concentration was significantly increased in trained diabetic rats (102±21 pg/ml vs 47±7 for control (P〈0.05) and vs 49±9 for sedentary diabetic (P〈0.05). These data indicate that a programme of physical training in diabetic rats can reduce both the total number and the density of beta-adrenoceptors in heart ventricular tissue, possibly by increasing the basal epinephrine secretion.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01908143
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