Respiratory and calcium transport properties of spiny lobster hepatopancreas mitochondria.
Mitochondria were isolated from the hepatopancreas of the Florida spiny lobster Panulirus argus using a high osmolarity medium containing 600 mM mannitol, 83 mM sucrose, 5 mM 4-morpholinepropanesulfonic acid, pH 7.6, 0.5% bovine serum albumin (BSA), and 1 mM EDTA. O2 uptake and Ca2+ transport were measured by electrode methods in similar media (plus 4 mM KPi, 3.3 mM MgCl2, and 0.67 mg/ml BSA, with 80 mM KCl replacing a portion of the osmotic support). Substrate-supported respiration was observed to be coupled to phosphorylation of ADP or uptake of Ca2+ ions. State 3 rates (nanogram atoms O X minute-1 X milligram protein-1 +/- SEM (N)) were: 49.2 +/- 3.9 (19), succinate; 30.9 +/- 3.9 (6), DL-palmitoyl carnitine; 29.0 +/- 2.7(9), L-malate; 40.0 +/- 2.3(3), L-glutamate; 27.7 +/- 2.2(5), D-3-hydroxybutyrate; and 26.4 +/- 2.4 (18), L-proline +/- pyruvate. alpha-Glycerol phosphate was not oxidized. Ca2+ uptake driven by succinate oxidation proceeded with Ca:O ratios of 4.0 +/- 0.2 (SEM). Hepatopancreas mitochondria were not uncoupled by Ca2+ uptake in excess of 1100 ng atoms X mg protein-1. Ca2+ efflux could be induced by ruthenium red, indicating the presence of an active Ca2+ cycle. These mitochondria may provide a favorable model system in which to study regulation of the Ca2+ cycle.