Intrinsic metabolic depression in cells isolated from the hepatopancreas of estivating snails

Many animals across the phylogenetic scale are routinely capable of depress ing their metabolic rate to 5-15% of that at rest, remaining in this state sometimes for years, However, despite its widespread occurrence, the bioche mical process;es associated with metabolic depression remain obscure, We de monstrate here the development of an isolated cell. model for the study of metabolic depression, The isolated cells from the hepatopancreas; (digestiv e gland) of the land snail (Helix aspersa) are oxygen conformers; i,e,, the ir rate of respiration depends on pO(2) Cells isolated from estivating snai ls show a stable metabolic depression to 30% of control (despite the long a nd invasive process; of cell isolation) when metabolic rate at the physiolo gical pH and pO(2) of the hemolymph of estivating snails is compared with m etabolic rate at the physiological pH and pO(2) of the hemolymph of control snails. When the extrinsic effects of pH and pO(2) are excluded, the intri nsic metabolic depression of the cells from estivating snails is still to b elow 50% of control snails. The in vitro effect of pO(2) on metabolic rate is independent of pH and state (awake or estivating), but the effects of pH and state significantly interact, This suggests that pH and state change a ffect metabolic depression by similar mechanisms but that the metabolic dep ression by hypoxia involves a separate mechanism.