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Journal of Experimental Biology 131,89-105 (1987)
Published by Company of Biologists 1987

Anaerobic Metabolism and Changes in Acid–Base Status: Quantitative Interrelationships and PH Regulation in the Marine Worm Sipunculus Nudus

HANS-OTTO PÖRTNER 1

1 Institut für Zoologie IV, Universität Düsseldorf, D-4000 Düsseldorf, FRG and Department of Biology, Acadia University, Wolfville, Nova Scotia, Canada BOP 1X0

The quantitative influence of anaerobic metabolism on acid—base status and on acid-base regulation is investigated in Sipunculus nudus L. Proton generation by metabolism is calculated from theoretical predictions. The quantitative comparison of metabolic protons with non-respiratory protons found in the acid–base status is performed assuming a simplified model of the total animal. Taking the protonequivalent ion exchange between animals and ambient water into account, changes in the anaerobic acid–base status can be explained exclusively by proton generation in metabolism. It is concluded that the classical concept of acid—base physiology is adequate and that the consideration of strong ions is not required for a quantitative treatment of the acid—base status.

The hypothesis that a quantitative correlation exists between metabolic and acid—base events is tested by comparing changes in acid—base status and in metabolism in animals exhibiting different metabolic rates. For this purpose, a method is developed for the calculation of intracellular pH from metabolite concentrations and extracellular acid—base parameters. Proton exchange between intra-and extracellular compartments, which is found to depend upon the total amount of accumulated non-respiratory protons, demonstrates that pHi is regulated even during anaerobiosis. The defended pH, value, however, is lower during anaerobiosis than during subsequent recovery.

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Key words: anaerobiosis, anaerobic metabolism, opines, octopine, strombine, succinate, propionate, acetate, protons, acid–base, pH regulation, intracellular pH, strong ions, Sipunculus nudus

Accepted on May 1, 1987






© The Company of Biologists Ltd 1987