Methacholine試験における交感神経機能の数量的指標としての血中catecholamine測定の意義

DETERMINATION OF PLASMA CATECHOLAMINE AS A QUANTITATIVE INDEX FOR THE EVALUATION OF SYMPATHETIC NERVOUS SYSTEM FUNCTION IN MAN DURING METHACHOLINE TEST

緒言

　Methacholine試験は古くから，ヒト交感神経機能検査として使用されてきた^1,2,3）。Methacholine注射により末梢性にひきおこされた血圧低下が頸動脈洞を介し，後部視床下部の交感神経中枢を賦活化し，この結果，血圧が上昇し，この血圧回復の様相が交感神経中枢の反応性の指標となると考えられてきた^2）。従つて，特異的で実際的なcatecholamine （CA）の測定法が確立していなかつたために血圧がmethachohne試験における唯一の交感神経機能の指標であつた。

　Dopamine—β—hydroxylase （DBH）は神経伝達物質のひとつであるnorepinephrine （NE）をdopamineから生成する酵素で交感神経終末のCA含有小包や副腎髄質のchromaffin顆粒内に存在し，各種刺激により，CAとともに血中に遊出することから，血漿DBH活性測定はヒト交感神経機能の指標として有用であることが報告された^4）。

For many years blood pressure has been only an index among a number of physiological conditions presenting sympathetic nervous systems activities in methacholine test due largely to the lack of specific and practical method for the determination of catecholaminc.

We found that methacholine induced a significant increase in plasma catecholamines with an alterna-tion in hemodynamic change in the present study by the use of high speed liquid chromatography and automated THI method.

The increments in plasma catecholamines were not correlated with apparent decrements in blood pressure. Therefore the increments in plasma catecholamines induced by methacholine were not attributable to reflex responses to hemodynamic changes and rather could be the direct effect of methacholine on sympathetic neuron and adrenal medullae. Besides there was no correlation between the increments in plasma catecholamines and metha-choline indices. These data question the suitability of blood pressure as an index for the evaluation of sympathetic nervous system function during methacholine test and suggest that plasma cate-cholamines might be a proper parameter for the sympathetic nervous activities response to metha-choline.