Effects of halothane on ventricular myocyte shortening and intracellular Ca²⁺ in streptozotocin-induced diabetic rats

We have investigated the effects of the general volatile anaesthetic halothane on ventricular myocyte shortening and intracellular Ca²⁺ in streptozotocin (STZ) - induced diabetic rats. Shortening and intracellular Ca²⁺ were measured in electrically stimulated myocytes superfused with either a normal Tyrode (NT) solution or NT containing 1 mM halothane. Experiments were performed at room temperature (25-26°C). Body weight and heart weight were lower and blood glucose concentration characteristically higher in rats at 8-12 weeks after STZ treatment. Contractile defects in myocytes from STZ-treated rats were characterized by prolonged time to peak (TPK) contraction. Halothane evoked a transient increase followed by a sustained decrease in amplitude of shortening in myocytes from control and STZ-treated rats. The magnitude of the sustained negative inotropic effect of halothane was significantly larger in myocytes from STZ-treated compared to control rats. Prolonged TPK contraction in myocytes from STZ-treated rats was not additionally altered by halothane. The amplitude of the Ca²⁺ transient was significantly reduced to similar extents by halothane in myocytes from control and STZ-treated rats. The time from peak to half relaxation of the Ca²⁺ transient was prolonged in myocytes from STZ-treated rats but was not additionally altered by halothane. Altered mechanisms of Ca²⁺ transport might underlie the contractile defects observed in myocytes from STZ-induced diabetic rat heart and the negative inotropic effects of halothane.