Effects of fasting on skeletal muscle contraction and cardiovascular function in rats / 中国医师杂志

ABSTRACT

Objective To investigate the effects of fasting with different time courses on the contraction of skeletal muscle and cardiovascular function in Sprague-Dawley (SD) rats.Methods The healthy and male SD rats were randomly divided into (1) control,(2) 12 h fasting,(3) 24 h fasting,and (4) 48 h fasting groups.After animal models of fasting with different time courses were established,the heart,thoracic aorta,soleus,and extensor digitorum longus (EDL) were rapidly isolated from rats under anesthesia and then fixed into the respective organ perfusion system that was connected to physiological recorders and data acquisition system.Langendorff heart perfusion was used to detect some parameters of cardiac function,including left ventricular systolic pressure (LVSP),left ventricular end-diastolic pressure (LVEDP),and maximum ascending and declining rate of left ventricular pressure (± dP/dt max).Then,the heart was suffered from 30 min ischemia followed by 60 min reperfusion,the changes in above cardiac function parameters were recorded again.The contraction response to potassium chloride or phenylephrine and endothelium-dependent relation responses to acetylcholine (ACh) of aortic rings were measured with organ bath.The changes of twitch tension and titanic tension of soleus and EDL were examined to reflect contractive function of skeletal muscle.Results The + dP/dt max was significantly reduced in 24 h and 48 h fasting groups compared to the control (P ＜ 0.01).After ischemia-reperfusion,the heart re-beat time was significantly longer [(24.3 ± 7.0)min vs (14.0 ± 2.9)min,P ＜0.05],both mLVDP and mLVP were significantly higher in 48 h and 24 h fasting groups than control group (P ＜ 0.05),and those changes did not normalized until re-perfusion 60 min.The 48 h fasting increased significantly endothelium-dependent relaxation of aortic rings response to low concentration acetylcholine (P ＜ 0.05),but did not affect the maximum relaxation of aortic rings response to high concentration acetylcholine and contraction of aortic rings responses to potassium chloride and phenylephrine.The 48 h fasting also enhanced significantly titanic tension of soleus compared to the control [(7.01 ± 1.22) N/cm2 vs (5.5 ± 0.75) N/cm2 for48 h-Fasting vs Control,P ＜0.05].Conclusions The 24 ～48 h fasting may induce inhibition of cardiac function,while fasting 48 h can increase the sensitivity of aortic rings responses to ACh and contraction function of soleus in healthy and male rats.