Effects of adrenaline on a compartment of slowly-exchangeable calcium in the perfused rat heart.
The effects of adrenaline on kinetically-distinct compartments of exchangeable calcium in the spontaneously-beating perfused rat heart were investigated under steady-state conditions using a 45Ca2+ outflow technique together with a nonlinear least-squares curve fitting procedure and 51Cr-EDTA to monitor the loss of freely-diffusible Ca2+ from the extracellular space. In addition to Ca2+ distributed in the vascular (compartment 1) and interstitial (compartment 2) spaces, the minimum number of kinetically-distinct compartments of cellular exchangeable Ca2+ (which include Ca2+ bound to extracellular sites on the sarcolemma) required to fit the data (compartments 3, 4 and 5) was three. A system in which cellular compartment 3 is linked to the vascular space and compartments 4 and 5 are linked to the interstitial space was consistent with the data. For hearts perfused under control conditions, the fractional transfer rates for Ca2+ outflow from cellular compartments 3, 4 and 5 were 0.70, 0.11 and 0.017 min-1, respectively. Adrenaline increased the quantity of exchangeable Ca2+ in compartment 5 and decreased that present in the compartment 4. Evidence that compartment 5 includes mitochondrial exchangeable Ca2+ is discussed. It is concluded that one of the actions of adrenaline on the heart is to increase the quantity of exchangeable Ca2+ in the mitochondria.
D000818:Animals; D001825:Body Fluid Compartments; D002118:Calcium / Q000378:metabolism*; D004492:Edetic Acid; D004837:Epinephrine / Q000494:pharmacology*; D006321:Heart / Q000187:drug effects; D066298:In Vitro Techniques; D007700:Kinetics; D008929:Mitochondria, Heart / Q000187:drug effects / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism*; D010477:Perfusion; D051381:Rats
D004492:Edetic Acid; D002118:Calcium; D004837:Epinephrine