The action of insulin on cardiac contractility in active, hibernating and arousing ground squirrels

During the deep hibernation (at 5-6 degrees C of the heart temperature) and during arousal from hibernation (at 15-16 degrees C) insulin have no effect on contractility. Two opposite inotropic effects of insulin at concentrations 0,1-50 nM were found at higher temperature of arousing: a transient positive inotropic effect between 21-28 degrees C, and a negative one (about 20-30% from the control value) above 28 degrees C. In active summer and winter animals insulin produced mainly the negative inotropic effect.