Duchenne型筋ジストロフィーにおける血清心筋ミオシン軽鎖I測定の臨床的意義—骨格筋障害との関連性

Clinical Significance of Serum Cardiac Myosin Light Chain I in Patients with Duchenne Muscular Dystrophy

　血清中の心筋ミオシン軽鎖I（以下LCIと略）を簡便に測定できるモノクロナール抗体が開発され心筋梗塞の診断に寄与している。

　我々はDuchenne型筋ジストロフィー（以下DMDと略）患者でLCIを測定したところ，加齢や障害度と共に低下を示し，また呼吸機能の指標である％VCの減少と共に低下することを確認した。この事実よりLCIは心筋障害ばかりではなく，骨格筋の機能障害とりわけ肺の換気障害との関係が注目され，人工呼吸器装着時期の判定指標の1つにもなり得ると考えられた。そこでこの抗体が心筋のみでなく骨格筋のミオシン軽鎖Iをもクロスして測定している可能性を検証するため，Westem blot法と免疫組織学的方法により検討した。その結果，心筋モノクローナル抗体は骨格筋27KD蛋白とクロスし，骨格筋の赤筋に優位に染色されることが判明した。

The cardiac myosin light chain I (LCI) is one of the cardiac muscle structual proteins. A sensitive immunoradiometric assay kit for LCI by using LCI monoclonal antibodies is developed.

We estimated LCI in the patients with Duchenne muscular dystrophy (DMD) and Kugelberg-Welan-der disease (KW). The results suggested that LCI has close relationships with the functional distur-bances of skeletal muscles, especially disturbances of pulmonary ventilation. Therefore we studied properties and localizations of LCI in the skeletal muscles by Western blotting and immunohisto-chemical methods.

In Western blotting method LCI monoclonal anti-bodies have a band of 27 KD proteins of skeletal muscles. LCI has also found to be localized in type 1 fibers in frozen sections of biopsied of human skeletal muscles.

LCI was measured from 47 patients with DMD and 8 patients with KW.

The average serum LCI levels in the patients with DMD were 11.79 ng/dl and its levels in the patients with KW were in the normal range (under 2.5ng/dl). Among 12 patients recieving negative pressure chest respirator, the levels of LCI were also under 2.5ng/ dl. Serum LCI decreased with increasing age and reduced physical activity. The levels of LCI has obvious positive correlations with CK and myog-lobin. These results suggested that the measure-ments of serum LCI are useful as one of the markers of disease severity and the determination of suitable time of using respirator.