Age-related Alterations of Bcl-2, Bax and Apoptosis in Ischemic-reperfused Rat Tibialis Anterior Muscles

Seo, Youn Kyoung; Kim, Jong Heon; Leem, Hyun Sung; Shin, Chae Soo; Paik, Doo Jin

Abstract

Prolonged ischemic-reperfusion induces cellular damages and apoptosis in rat skeletal muscle. Such injury takes place in the phase of reperfusion following ischemia induction in part via regulating of apoptosis-related gene inductions. Among apoptosis-related gene products, Bcl-2 and Bax regulate the apoptotic response by inhibiting and promoting cell death, respectively. The present study was performed to examine the age-related alertation of expression of Bcl-2 and Bax along with apoptosis in rat tibialis anterior muscles following ischemia-reperfusion. 9 weeks, 30 weeks and more than 65 weeks old male Sprague-Dawley rats were divided into 2 groups such as controls, 4 hour ischemia. 4 hour ischemia group was divided into 3 subgroups based on reperfusion time. For ischemia, left commom iliac artery was occulded for 4 hours. The tibialis anterior muscles were removed 0, 3, and 24 hours after onset of reperfusion. Muscle samples were embeded in paraffin and 6 micrometer sections were made. The expression level of Bcl-2 and Bax were examed using immunohistochemical methods and apoptotic reactions was detected using TUNEL methods. The results obtained were as follows; 1. In control group, Bcl-2 and Bax were weakly immunostained in 9 weeks old rat tibialis anterior muscles. In 30 and 65 weeks old rat tibialis anterior muscles, Bcl-2 immunostaning was minimal. The level of Bax staining was increased in 30 and 65 weeks old rat tibialis anterior muscles, compared with those of 9 weeks old rats. The level of apopto-sis among different age groups were not altered. 2. In the 4 hour ischemia group, the level of Bax staining was correlated with the level of apoptosis in 9 weeks, 30 weeks and 65 weeks old rat tibialis anterior muscles. 3. The level of apoptosis was increased in older groups relative to younger groups in 4 hour ischemia. These results suggested that the level of apoptosis induced by ischemic-reperfusion in tibialis anterior muscle increase with ageing in rat tibialis anterior muscles, and that a increase of Bax expression is related to increased apoptosis.