The Effect of Halothane on the Sarcoplasmic Reticulum in Normal and Right Ventricular Hypertrophy in Rabbits

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Abstract

Calcium accumulation and storage by the sarcoplasmic reticulum is affected adversely by both inhaled anesthetics and hypertrophy. The interaction of these two conditions in right ventricular muscle was examined in a skinned fiber preparation whereby the sarcolemma was disrupted mechanically to permit external control of the chemical composition of the cytoplasm. Skinned fibers were obtained from the right ventricles of rabbits 4 mo after surgical banding of the pulmonary artery (n = 5) or sham banding (n = 4). Right ventricles after pulmonary artery banding weighed an average of twice that of normal right ventricles. The sarcoplasmic reticulum of the skinned fibers was permitted to accumulate Ca2+ and then maximal or submaximal Ca2+ release was induced with 25 mM or 2 mM caffeine, respectively. The magnitude of the Ca2+ release was estimated by the area of the ensuing tension over time. When 1%, 2%, or 3% halothane accompanied the 2 mM caffeine, both normal and hypertrophied muscle exhibited an area of the tension transient twice that of the tension transients without halothane (control). When present during Ca2+ accumulation, 1%, 2%, and 3% halothane reduced the 25 mM caffeine-induced tension transient in normal and hypertrophied muscle to 36%, 17%, and 11%, respectively, of the controls. The equal depression in normal and hypertrophied right ventricles was in contrast to a previous study in which hypertrophy provided some protection against the decrease in sarcoplasmic reticulum Ca2+ storage by halothane. The authors concluded that halothane enhances Ca2+ release from the sarcoplasmic reticulum in normal and hypertrophied right ventricular muscle in rabbits and that right ventricular hypertrophy did not protect against the marked inhibition by halothane of Ca2+ storage in sarcoplasmic reticulum.

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