Effects of Propofol on Calcium Homeostasis in Human Skeletal Muscle

Abstract

Malignant hyperthermia is a pharmacogenetic skeletal muscle disorder of intracellular calcium (Ca²⁺) homeostasis with an autosomal dominant inheritance. The objective of this study was to investigate the safety of propofol by investigating its effects on calcium homeostasis and its effect sites in human skeletal muscles.

Muscle specimens were obtained from 10 individuals with predisposition to malignant hyperthermia. In skinned fibre experiments, we measured the effects of propofol on the Ca²⁺-induced Ca²⁺ release and the uptake of Ca²⁺ into the sarcoplasmic reticulum. Ca²⁺ imaging in primary myotubes was employed to analyse propofol-mediated alternations in the Ca²⁺ regulation and propofol-induced Ca²⁺ responses in the presence of Ca²⁺ channel blocker or Ca²⁺-induced Ca²⁺ release inhibitor.

Increased Ca²⁺ release from the sarcoplasmic reticulum and inhibition of Ca²⁺ uptake into the sarcoplasmic reticulum were not observed with 100 μM propofol. A rise of Ca²⁺ was not seen under 100 μM propofol and the EC₅₀ value for propofol was 274.7±33.9 μM, which, is higher than the clinical levels for anaesthesia. Propofol-induced Ca²⁺ responses were remarkably attenuated in the presence of Ca²⁺ channel blocker or Ca²⁺-induced Ca²⁺ release inhibitor compared with the results obtained with caffeine.

We conclude firstly that propofol is safe for individuals with predisposition to malignant hyperthermia when it is used within the recommended clinical dosage range, and secondly that its mode of action upon ryanodine receptors is likely to be different from that of caffeine.