On the effect of glucagon on mitochondrial calcium retention in isolated hepatocytes.
Exposure of isolated hepatocytes to glucagon for 45 min caused a 2.5-fold increase in the time (Ca2+ retention time) for which mitochondria subsequently isolated from the cells retained a load of exogenous Ca2+ before its spontaneous release. Half maximal effect of glucagon was observed at a concentration of 0.6 nM. An increase in the Ca2+ retention time was observed after 30 but not 15 min exposure of cells to the hormone. Incubation of hepatocytes with dexamethasone, epinephrine, vasopressin, dibutyryl cyclic AMP or 8-bromo cyclic GMP also induced an increase in mitochondrial Ca2+ retention time. The effect of glucagon was associated with an increase in cellular cyclic AMP and was inhibited by puromycin, cycloheximide and cordycepin, but not by actinomycin D or chloramphenicol. Puromycin caused only a small inhibition of the stimulation by glucagon of mitochondrial pyruvate carboxylation. It is concluded that the effects of glucagon on mitochondrial Ca2+ retention require nuclear DNA-directed protein synthesis and differ, in this respect, from the rapid-onset effects of the hormone on other mitochondrial properties, including pyruvate carboxylation.
D000818:Animals; D001639:Bicarbonates / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D005934:Glucagon / Q000494:pharmacology*; D066298:In Vitro Techniques; D008930:Mitochondria, Liver / Q000187:drug effects / Q000378:metabolism*; D014176:Protein Biosynthesis; D011773:Pyruvates / Q000378:metabolism; D019289:Pyruvic Acid; D051381:Rats
D001639:Bicarbonates; D011773:Pyruvates; D019289:Pyruvic Acid; D005934:Glucagon; D002118:Calcium