Adenylate compartmentation and storage in coelomic cells of the polychaete Nereis virens

The concentrations of adenine nucleotides (AMP, ADP, ATP) were determined in coelomic cells (eleocytes) of the polychaete Nereis virens. In cells of immature and male animals, total ADP and AMP contents (each 10­15 µmol ml-1 packed cell volume) greatly exceeded that of ATP (0.8 µmol ml-1 packed cell volume). 31P-nuclear magnetic resonance (NMR) studies of living eleocytes showed that the high concentrations of both AMP and ADP are free in solution. Comparisons of in vivo NMR spectra with those obtained from metabolite extracts of eleocytes suggest that the adenylate pools are compartmentalized, with a large pool being in an environment with a pH<6.0 and a small pool being in a domain where pH>6.7. This indicates that eleocytes are capable of storing high concentrations of ADP and AMP without inhibiting energy metabolism by sequestering these compounds into an acidic compartment. The large acidic vacuole characteristic of eleocytes may function as this compartment.