The Effects of Heat and Cold Exposure on the Adjuvant Arthritis in Lewis Rats

本研究では,アジュバント関節炎ラットの後肢に42℃の高温刺激と10℃の低温刺激を負荷し,関節炎の病態におよぼす影響とヒラメ筋の廃用性筋萎縮の進行抑制効果を検討した。7週齢のLewis系雌ラット31匹を生理食塩水を投与する非関節炎群15匹と起炎剤を投与する関節炎群16匹に分け,各々の群を通常飼育群,高温刺激群,低温刺激群に分けた。そして,高温,低温刺激は起炎剤投与1週後から2週間,1日1時間,週5回負荷した。高温刺激ではタイプI,II線維とも廃用性筋萎縮の進行抑制効果を認めたが,低温刺激ではタイプI線維のみでしか効果を認めず,このことから廃用性筋萎縮の進行抑制に対しては低温刺激より高温刺激が効果的であることが示唆された。しかし,関節炎の病態に対しては高温刺激により悪影響があり,これらのことを総合的に判断するとアジュバント関節炎に対しては低温刺激が安全かつ有効な方法と思われる。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 weekold, 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