Correlation between halothane-induced myocardial depression and decreases in La3+-displaceable Ca2+ in cardiac muscle...

The relationship between myocardial contractility and the amount of La3+-displaceable Ca2+ was studied in the presence and absence of halothane using dog trabecular muscle. The La3+-displaceable Ca2+ is believed to represent surface-located Ca2+ which enters the cytoplasm and interacts with the contractile proteins during membrane depolarization. It was found that there was a linear relationship between the halothane-induced decrease in contractility and the reduction in the amount of La3+-displaceable Ca2+. Additional data suggest that halothane increases the Ca2+ binding of the plasma membrane, thereby decreasing the availability of the surface-located Ca2+.