Anaerobic metabolism in the leech (Hirudo medicinalis L.): direct and indirect calorimetry during severe hypoxia |
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Authors: | H Schmidt A Wichmann I Lamprecht I Zerbst-Boroffka |
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Institution: | (1) Institut für Tierphysiologie der Freien Universität Berlin, Grrunewaldstrasse 34, D-12165 Berlin, Germany;(2) Institut für Biophysik der Freien Universität Berlin, Thielallee 63, D-14195 Berlin, Germany |
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Abstract: | Anaerobic metabolism in the limnic annelid Hirudo medicinalis L. was investigated by direct and indirect calorimetry. During long-term severe hypoxia, the rate of heat dissipation was reduced up to 13% of the aerobic rate. At the same time, the rate of ATP turnover was reduced to about 30% of the aerobic rate, indicating that metabolic depression is an important mechanism to ensure survival of the leech during environmental anaerobiosis. Heat dissipation during hypoxia was monitored under two experimental conditions, favouring either concomitant hypocapnia (continuous N2 bubbling) or hypercapnia (self-induced hypoxia). The reduction in heat dissipation during hypocapnic hypoxia was less pronounced than during hypercapnic hypoxia, indicating that the different experimental conditions may influence anaerobic metabolism and the extent of metabolic depression. Biochemical analysis of known anaerobic substrates and endproducts provided the basis for indirect calorimetry during self-induced hypoxia. From changes in metabolites, the expected heat dissipation was calculated for initial (0–8 h) and long-term severe hypoxia (8–72 h). During the initial period, the calculated heat dissipation fully accounted for direct calorimetric determination. During long-term hypoxia, only 71% of the measured heat production could be explained from biochemical analysis of metabolites. Therefore, an additional unknown endproduct cannot be excluded, especially when anaerobic ammonia production and analysis of the carbohydrate balance are considered.Abbreviations
APW
artificial pond water
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HPLC
high-performance liquid chromatography
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fw
fresh weight
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HP
heat production
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HD
heat dissipation
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MR
metabolic rate |
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Keywords: | Anaerobic metabolism Direct calorimetry Indirect calorimetry Hypocapnic and hypercapnic hypoxia Leech Hirudo medicinalis |
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