It has been shown that many diseases are linked to abnormalities of the erythrocyte membrane. This study observed the changes in erythrocyte membrane fluidity during an immobilization period of 21 days. The right hindlimbs of male adult New Zealand white rabbits were immobilized for 21 days. Blood samples were collected and heparinized prior to immobilization and on days 1, 3, 7, 14, and 21 of immobilization. The membrane fluidity of erythrocytes was measured by spin-label electron spin resonance (ESR). The membrane fluidity was expressed by the value of order parameter (S). The results showed a significant increase of S on days 7 and 14 of immobilization (p <0.01). The highest value of S was found on day 7 of immobilization; thereafter, S gradually declined. Compared with the value measured before immobilization, there was no significant difference in the value of S on day 21. The results show that immobilization significantly affected erythrocyte membrane fluidity, indicating a systemic and temporal response ofthe immobilized body. This study is the first to document the time-course of changes in erythrocyte membrane fluidity in rabbits with single hindlimb immobilization during 21 days. These results may be helpful in studying the pathophysiology of immobilization.
Higher oxidative stress reportedly plays a key role in muscle damage caused by immobilization and subsequent remobilization. However, we have no clear understanding regarding oxidative stress during immobilization and remobilization. The purpose of this study was to clarify the characteristics of oxidative stress by measuring oxidative stress locally and systemically. Twenty-three New Zealand White rabbits were used in this study. Blood samples were collected on Days 1, 3, 7, 14, and 21 of immobilization, and Days 1, 2, 3, and 4 of remobilization. The soleus muscles in immobilized and nonimmobilized limbs were harvested on Day 21 of immobilization and Day 7 or Day 14 of remobilization. Muscle wet weight was determined as the indicator of muscle atrophy. The levels of lipid peroxidation and glutathione in plasma and soleus muscles were measured. Immobilization and remobilization induced an increase in the lipid peroxidation levels and a decrease in glutathione levels in muscle and blood. These findings suggest that oxidative stress occurs locally and systemically, lasts throughout the immobilization period, but peaks at the early phase of remobilization.
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