[Effect of ketamine on the Ca(2+)-related functions of skinned skeletal muscle fibers from the guinea pigs].

To determine whether ketamine has a possibility to predispose a patient to malignant hyperthermia (MH), the author investigated the effects of ketamine on the intracellular calcium kinetics with the skinned fiber technique in skeletal muscle cells of guinea pigs. Intracellular calcium kinetics including calcium induced calcium release (CICR) from sarcoplasmic reticulum (SR), calcium uptake into SR, and sensitivity of contractile proteins for calcium were assessed by using calcium concentration-response relationships. The effects of ketamine on the calcium concentration-response curves, which were constructed by changing calcium concentration from 10(-7) to 10(-4.5) M, were determined with ketamine concentrations of 0.1, 0.3, 1.0 and 3.0 mM. The author found that the rate of CICR was not altered with any ketamine concentration, while initial rate of calcium uptake into SR decreased and calcium rate (pCa)-tension curves shifted leftward with ketamine concentration of 3 mM at low concentrations of Ca2+ (below pCa 5.5). Thus, ketamine is not associated directly with occurrence of MH because ketamine has no significant effects on CICR. However, an increase in intracellular calcium concentration due to depressed calcium uptake into SR and an increased sensitivity of contractile proteins for calcium may lead to symptoms and signs like MH.