中耳手術におけるドリルの振動が,手術後の感音難聴の原因の一つと考えられている。モルモットを用いて耳小骨にドリル誘発性損傷を与えた結果,血管条血管の透過性がドリル振動時間に依存して有意に増加していることが報告されている。今回は振動負荷後の血管条血管の透過性亢進を防止させることを目的とし,振動負荷前にステロイドを投与し,振動負荷後の血管条血管の透過性の変化を検討した。血管透過性のトレーサーとしてhorseradish peroxidase(HRP)を使用し,hydrocortisone,HRP静注後60秒間ドリル振動負荷を耳小骨に与え,電子および光学顕微鏡下にHRPの血管条内の動向を検討した。その結果,振動負荷前にステロイドを静注することによって,血管条血管からのHRP漏出が減少していることが確認された。これは投与されたステロイドが,ドリル振動負荷により充進する血管条血管の透過性を抑止したものと考えられた。ドリル振動負荷による血管条血管の透過性亢進は血管内皮細胞の損傷によるものと考えられ,活性酸素の関与が推測された。, Vibration by a drill in middle ear surgery is considered to be one of the causes of perceptive deafness after surgery. It is reported that drilling-induced injury of the auditory ossicles in guinea pigs significantly increased the permeability of blood vessels of the stria vascularis, depending on the drilling vibration time. In this study, we administered steroid before vibration in order to prevent increased permeability of blood vessels of the stria vascularis after vibration, and examined the change in permeability of the blood vessels after vibration. Guinea pigs were divided into three groups (groups A, B, and C). hen 100 mg hydrocortisone was administered to each animal in group A, 50 mg hydrocortisone to each in group B, and bydrocortisone was not administered in group C, as a control group. As a tracer of permeability of blood vessels, horseradish peroxidase (HRP) was used. HRP in the stria vascularis was examined by electron and light microscopy. Permeability of blood vessels of the stria vascularis was classified according to the degree of leakage of HRP type I, no leakage of HPR from capillaries type II, slight leakage of HRP : type III, leakage of HRP all around blood vessels ; and type IV, leakage of HRP from blood vessels and the presence of HRP in the stroma. In groups A and B, the percentage of type I was significantly higher than in group C. In contrast, the percentage of type III and IV was higher in group C than in groups A or B. Therefore, it was confirmed that intravenous injection of steroid before vibration decreases the leakage of HRP from blood vessels of the stria vascularis. It was speculated that the increase in permeability of blood vessels by drilling vibration is due to injury of endothelial cells and may involve active oxygen.