心筋筋小胞体機能と左心室拡張期特性

Function of cardiac sarcoplasmic reticulum and left ventricular diastolic properties

　心室拡張期事象のうち。主に早期には能動的な弛緩特性が，後期には受動的な心筋弾性特性が関与すると考えられている。この早期の能動的弛緩特性には，興奮—収縮連関系、特に心筋筋小胞体が関与しており，筋小胞体による収縮蛋白系からの能動的Ca^2＋取り込み作用が，心筋弛緩開始のtriggerとなるとされている^1）。ここでもし何らかの原因によって筋小胞体機能が障害されると，当然，心室拡張特性ひいては収縮特性に影響を受けると考えられる。

　今回，実験的に慢性容積負荷心を作製し，その拡張期心機能と筋小胞体機能との関連性について検討してみた。

The relation between function of cardiac Sarco-plasmic Reticulum (SR) on the molecular level and left ventricular diastolic properties on the ventricu-lar chamber level was studied in various stages of chronically volume overloading canine hearts in-duced by complete A-V block.

Initial Ca²⁺-Binding rate and max Ca²⁺-Binding capacity of cardiac SR were measured by a dual-beam spectrophotometric assay procedure. And left ventricular diastolic hemodynamics (negative dp/dt, time constant T, dv/dp, k, and Δv/Δp) were evaluated by pressure-volume relationship using trans-epicardial echocardiographic technique.

In this study the following results were obtained, (1) Left ventricular diastolic indices were re-duced with the progress of eccentric hypertrophy by chronic volume overload.(2) Cardiac SR function was impaired by chron-ic volume overload. This cause was not failed to show clearly, but it was suspected that it had some-thing to do with eccentric hypertrophy.

( 3) Ca²⁺-Binding activity of SR beared a close interrelation with left ventricular diastolic indices, especially with time constant T.