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

摘要

The effect of insulin (0.1-100 nM) on isometric force of contraction in isolated ground squirrel papillary muscle was investigated. In summer autumn and winter active animals, insulin had a negative inotropic effect on papillary muscles, decreasing the amplitude of contraction by about 30% of the control value. In some cases, predominantly in the summer group of animals, insulin produced different effects on contractility: ow doses (0,1-0.5 nM) caused a transient activation of isometric contraction by about 10-15% of control, whereas high doses produced a negative inotropic effect by about 30% of the control level. During deep hibernation (at 5-6 deg C of heart temperature) and during arousal from hibernation (from 3 to 20 deg C), insulin had no significant effect on contractility. Opposite inotropic effects of insulin at concentrations of 0.1-50 nM were found during arousal:from 26 to 31 deg C of heart temperature - a positive inotropic effect by about 20-25% of control, and from 32 to 36 deg C - a negative one by about 30-40% of the control value.