Effects of halothane on contraction and intracellular calcium in ventricular myocytes from streptozotocin-induced diabetic rats

Background. Some of the cellular targets affected by volatile anaesthetics (e.g. halothane) which contribute to the negative inotropic effects of these agents are also affected during the progression of diabetic cardiomyopathy. A previous report suggested that halothane inhibited contraction to a lesser extent in papillary muscle from diabetic animals and so the aim of this study was to investigate possible mechanisms underlying this effect. Methods. Contractility and cytosolic calcium ion (Ca²⁺) transients were measured (fura-2) in ventricular myocytes isolated from control and streptozotocin (STZ)-induced diabetic rats in the absence and presence of halothane 0.6 mmol litre^-1 at 1 Hz stimulation. Sarcoplasmic reticulum (SR) Ca²⁺ content was assessed by rapid application of caffeine. All experiments were carried out at 36-37°C. Results. The amplitude of shortening, the electrically evoked Ca²⁺ transient, SR Ca²⁺ content and myofilament Ca²⁺ sensitivity, though not altered by STZ treatment, were significantly reduced by halothane to a similar extent in control and STZ myocytes. The time course of contraction and Ca²⁺ transient were prolonged in myocytes from STZ-treated rats compared with controls but this was not altered further by halothane. STZ treatment appeared to reduce Ca²⁺ efflux from the cell, an effect reversed by halothane. Conclusions. In contrast to a previous report, we could find no evidence of amelioration of the negative inotropic effect of halothane in myocytes from the STZ-induced diabetic rat. Contractility, the cytosolic Ca²⁺ transient, SR Ca²⁺ content and myofilament Ca²⁺ sensitivity were qualitatively similar in control and STZ myocytes and were all depressed to the same extent by halothane.