Abstract
The influence of intracellular pH (pH~i~) on the energy metabolism during hypoxia was studied in the lugworm Arenicola marina using in vivo ^31^P nuclear magnetic resonance (NMR) spectroscopy and biochemical analysis of the metabolic end products during hypoxia. By addition of phenylphosphonic acid (PPA) to the incubation medium to increase the extracellular H^+^ buffering capacity, different degrees of intracellular acidosis during hypoxia could be attained.
At low extracellular PPA concentrations pH~i~ dropped within 12 h of hypoxia from 7.3 to 6.7. High extracellular PPA concentrations (50 mM) kept pH~1~ stable at 7.2. Glycogenolysis was enhanced during hypoxia at high pH~i~, as shown by the measured amounts of accumulated end products. ATP production at high pH~i~ was 31 μmol/g h vs. 15 at low pH~i~‐ The mobilisation of the phosphagen phosphotaurocyamine (PTC) was, in contrast, decreased at high pH~i~: the ratio PTC/β‐ATP dropped from 4.8 (normoxia) to 2.8 at high vs. 1.3 at low pH~i~. The reduction of the metabolic rate during hypoxia hence depends on intracellular acidosis: the rate of the Embden‐Meyerhof‐Parnas pathway at high pH~i~ was 4.5 μmol/g h vs. 1.9 at low pH~i~.