In vivo NMR-studies of fish eggs. Monitoring of metabolite levels, intracellular pH, and the freezing and permeability of water in developing eggs of plaice, Pleuronectes platessa L.

Abstract

Using high resolution ³¹P-NMR the most abundant phosphorus containing metabolites (phospholipids, orthophosphate (P_i), and sugar phosphates) were simultaneously observed and quantified. An acidic yolk sac compared to the neutral pH of the larvae was demonstrated by their separated P_i lines.

Water inside the eggs gave rise to a downfield shifted proton NMR line relative to that of bulk water.

At low temperature, from −9 to −16° C, the freezing of intracellular water was directly observed as a gradual reduction and disappearance of its NMR line.

By quickly transferring the eggs into an NMR tube containing D₂O enriched seawater, the exchange rate of water was obtained from the observed time course of the change in the relative intensity of the two water NMR lines. The effects of temperature and salinity were studied. In the presence of toxic oils the permeability always increased. This effect was found to be correlated with the amount and presumed toxicity of oil present.