Fig. 3

Representative traces of a strip of the right ventricle of a rat heart showing A the contractile effect of glucagon (1–1000 nM) alone and, after washing, in the presence of 30 µM IBMX B, which increased contractility on its own and enhanced the inotropic effect of glucagon. C Cumulative concentration‒response curves showing the inotropic effect of glucagon alone (●) and in the presence of 30 µM IBMX (■). Contractility in the presence of IBMX was used as the baseline value for the second concentration‒response curve of glucagon. Inotropic responses are expressed as percent contractility increase compared to baseline. Each point represents the mean value ± SEM (vertical bars) of 5 experiments. *P < 0.05 compared to baseline (paired Student’s t test)