Recovery after anaerobic metabolism in the leech (Hirudo medicinalis L.)

Abstract

Medicinal leeches (Hirudo medicinalis L.) responded to self-induced hypoxia (72 h) with typical anaerobic metabolism characterized by a decrease in adenylate energy charge, utilization of the substrates glycogen and malate, and accumulation of the main anaerobic endproducts succinate and propionate. Propionate was also excreted into the medium. Ammonia excretion was suppressed. Aerobic recovery resulted in a profound O₂ debt. Resynthesis of ATP was completed within 30 min. Disposal of succinate and restoring of malate required 2–3 h, and clearance of propionate and recharging of glycogen 6–12 h. Ammonia excretion did not exceed normoxic rates and excretion of propionate during recovery accounted for only 10% of total propionate accumulated during hypoxia. It is postulated that the clearance of succinate and propionate involves oxidation but also resynthesis of malate and glycogen. During hypoxia and recovery blood osmolality remained constant. The Na⁺ and Cl^- ion concentrations in blood, the decrease of which was nearly equimolar during hypoxia, were re-established following different time-courses. Na⁺ concentration returned to normoxic levels after 2–3 h. The delayed increase in Cl^- concentration, however, correlating with 6–12 h necessary to clear blood propionate, is interpretated as an anion regulating effect.