دانلود رایگان مقاله انگلیسی اثرات آنالوگ آدنوزین و متیل کزانتین بر حساسیت انسولین در عضله سولوس موش صحرایی به همراه ترجمه فارسی
|عنوان فارسی مقاله:||اثرات آنالوگ آدنوزین و متیل کزانتین بر حساسیت انسولین در عضله سولوس موش صحرایی|
|عنوان انگلیسی مقاله:||Effects of analogues of adenosine and methyl xanthines on insulin sensitivity in soleus muscle of the rat|
|رشته های مرتبط:||زیست شناسی، علوم جانوری، علوم سلولی و مولکولی و بیوشیمی|
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|نشریه||الزویر – Elsevier|
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The concentration of insulin that produces half-maximal stimulation of glycolysis by stripped soleus muscle preparations is markedly increased by the adenosine analogues, 2-chloroadenosine and I@-phenylisopropyladenosine, but is markedly decreased by the methyl xanthine analogue, 8-phenyltheophylline. 2-Chloroadenosine increases the concentration of insulin required to stimulate glycolysis half maximally, from about 100 to 2OOO~units/ml. 8-Phenyltheophylline decreases this concentration of insulin from about 100 to 10 punits/ml, an effect which is similar to that produced either by addition of adenosine deaminase to the medium or to exercise-training of the donor animals for 4 weeks.
Insulin stimulates the rates of glycolysis and glycogen synthesis in muscle [ 11. Evidence has been obtained that adenosine, which is produced endogenously in muscle, decreases the sensitivity of glycolysis to insulin, but does not change the sensitivity of the process of glycogen synthesis. Thus, the presence of adenosine deaminase (ADA) in the incubation medium (which decreases the concentration of adenosine) decreased the concentration of insulin required to produce half-maximal stimulation of glycolysis in isolated soleus muscle from -100 to 10 /units/ml . The effect of ADA was abolished by the addition of the adenosine analogue, N6- p h eny 1’ isopropyladenosine (PIA). Adenosine has many functions as a local messenger in different tissues [3,4] and most, if no all, of these effects are mediated by binding to an extracellular receptor known as the ‘R-site’ [۵,۶]. It is suggested that analogues of adenosine (e.g., PIA) act as adenosine agonists for this site whereas methyl xanthine analogues (e.g., 8-phenyltheophylline (PTh)) act as antagonists [7,8]. If adenosine influences insulin sensitivity through this receptor, it is predicted that adenosine analogues should decrease insulin sensitivity of muscle glycolysis to insulin whereas methyl xanthine analogues should increase this sensitivity. The effects of two adenosine analogues, 2-chloroadenosine (2ClAdo) and PIA, and two methyl xanthine analogues, isobutylmethylxanthine (MIX) and PTh, on the sensitivity of glycolysis, glycogen synthesis and glucose oxidation to insulin in the isolated stripped soleus muscle preparation have been investigated and the results are presented and discussed here.
۲٫ MATERIALS AND METHODS
Animals, chemicals and enzymes were obtained from the sources in , except for [U-‘۴C]glucose, which was obtained from the Radiochemical Centre (Amersham), PIA which was obtained from Boehringer (Lewes, E. Sussex) and 2ClAdo, MIX and PTh which were obtained from Sigma (London). Rats were killed by cervical dislocation and the soleus muscle from each leg carefully exposed. The soleus muscle was divided into two strips of 25-35 mg as in [9,10] and attached to stainless steel clips and transferred directly to 4 ml KrebsRinger bicarbonate buffer at pH 7.4, containing 1% de-fatted albumin (which had been dialysed overnight against the buffer) and 5 mM glucose, in 25 ml siliconised Erlenmeyer flasks at 37°C (see [lo] for details). The buffer had been pregassed with OJCO2 (95 : 5) for 30 min. The strips were pre-incubated for 30 min, transferred to another flask containing the same medium except for the presence of 5 mM glucose containing [U-14C]glucose (0.25 &i/ml) and insulin at O-10 munits/ml (see table and figs for details) and incubated for a further 60 min. The flasks were gassed continuously during the preincubation and also for the first 15 min of the incubation period. The incubation was terminated, the muscle and incubation medium treated and the rate of lactate formation, glycogen synthesis and carbon dioxide production measured as in .