Abstract
The purpose of this study was to examine the effects of heat and cold exposure on inflammation, joint destruction, and skeletal muscle in rats with adjuvant arthritis. Thirty-one Lewis rats (7 week-old, female) were divided randomly Into 6 groups: control (n=5), heat-exposed (H, n=5), cold-exposed (C, n=5), adjuvant arthritis (AA, n=6). AA plus heat-exposed (AAH, n=5) and AA plus cold-exposed (AAC, n=5). AA was induced via intradermal injection of complete Freund's adjuvant (3.0 ml) into the center of the back region. One week after the injection, bilateral hindlimbs of the H and AAH groups were immersed in hot water (42℃) for 60 min/day, 5 days/week for 2 weeks. Similarly, bilateral hindlimbs of the C and AAC groups were Immersed in cold water (10℃). Upon comparison to the AA group, which were obtained through disuse of skeletal muscle, the AAH group displayed an increase in diameter of types I and 11 muscle fiber in the form of elevated heat shock protein 70; however, an accelerated ankle joint destruction was observed. On the other hand, the AAC group exhibited decreased inflammation and an increase in diameter of type I muscle fiber characterized by increased capillary number In soleus when compared to the AA group. These results demonstrate that heat and cold exposure afford a preventive effect with respect to muscle atrophy by disuse in AA rats; furthermore, cold exposure may be applied more safely than heat exposure.
