The effects of varying Ca++ concentration of the muscle bath on the total calcium content and contractility of malignant hyperthermia susceptible (MHS) and control pig muscle were measured. Muscle strips were incubated for 1 hr in Krebs-Ringer solutions containing 0, 0.5, 1, 2 and 2.5 mM Ca++, after which the total calcium content of each muscle strip was measured. Total magnesium and calcium content of MHS muscle was lower than control muscle at each Ca++ concentration tested. As Ca++ concentration of the bath was decreased from 2.5 to 0.5 mM, the calcium content of control muscle decreased proportionally. In contrast, only small changes in total calcium content of MHS muscle occurred as Ca++ concentration of the bath was varied. When the concentration of Ca++ was changed from 2.5 mM to a lower concentration, twitch tension of MHS muscle decayed in proportion to the Ca++ concentration of the bath. In contrast, only a small decay of twitch tension occurred in control muscle as Ca++ concentration was lowered. The abnormal contracture response of MHS muscle to 3% halothane decreased when the Ca++ concentration of the bath was below 1 mM and was essentially blocked when Ca++ was omitted from the bath. Contracture responses of MHS and control muscle to caffeine decreased with the Ca++ concentration of the bath. Contracture responses to lower caffeine doses (0.5-4 mM) were more affected by Ca++ concentration than were the contracture responses to higher (8-32 mM) caffeine doses. These observations are discussed in view of a thesis that the MHS muscle defect is associated with a Ca++ pool in muscle that is in equilibrium with the extracellular Ca++.
|Original language||English (US)|
|Number of pages||5|
|Journal||Journal of Pharmacology and Experimental Therapeutics|
|State||Published - 1981|
ASJC Scopus subject areas
- Molecular Medicine