The effects of glucagon and epinephrine on two preparations of cardiac mitochondria

The effects of $\text{in}$$\text{vivo}$ administration in epinephrine on calcium uptake were measured in two preparations of heart mitochondria, intermyofibrillar (IMF) and subsarcolemmal (SSL) using either ⁴⁵Ca²⁺ or murexide to follow calcium movement. The administration of either hormones resulted in an increased calcium uptake in both preparation of mitochondria subsequently isolated. This increase might be the consequence of the increased State 3 respiration, also evoked by hormones. The possibility is raised that the inotropic actions of glucagon and epinephrine might be partially mediated by mitochondria.