Interaction of halogenated anesthetics with α- and β-adrenoceptor stimulations in diabetic rat myocardium

Background: Halogenated anesthetics potentiate the positive inotropic effects of alpha- and beta-adrenoceptor stimulations. Although diabetes mellitus induces significant myocardial abnormatities, the interaction of halogenated anesthetics and adrenoceptor stimulation in diabetic myocardium remains unknown. Methods: Left ventricular papillary muscles were provided from healthy and streptozotocin-induced diabetic rats. Effects of 1 minimum alveolar concentration halothane, isoflurane, and sevoflurane on the inotropic and lusitropic responses of a (phenylephrine)- and beta(isoproterenol)-adrenoceptor stimulations were studied at 29degreesC with 12pulses/min. Data shown are mean percentage of baseline active force +/- SD. Results: Phenylephrine induced comparable positive inotropic effects in healthy and diabetic rats (143 +/- 8 us. 136 +/- 18%; not significant), but the potentiation by halogenated anesthetics was abolished in the diabetic rats (121 20, 130 20, and 123 +/- 20% for halothane, isoflurane, and sevoflurane, respectively; not significant). In diabetic rats, the positive inotropic effect of isoproterenol was markedly diminished (109 9 vs. 190 +/- 18%; P < 0.05), but its potentiation was preserved with isoflurane (148 +/- 21%; P < 0.05) and sevoflurane (161 +/- 40%; P < 0.05) but not with halothane (126 +/- 16%; not significant). Halothane induced a deleterious effect on the sarcoplasmic reticulum, as shown by its impairment in the lusitropic effect of isoproterenol, compared with isoflurane and sevoflurane. Conclusion: Potentiation of the positive inotropic effect of a-adrenoceptor stimulation by halogenated anesthetics is abolished in diabetic rats. In contrast, potentiation of beta-adrenoceptor stimulation is preserved with isoflurane and sevoflurane but not with halothane, probably because of its deleterious effects on sarcoplasmic reticulum.