Determination of high-energy phosphate compounds in fish muscle:31P-NMR spectroscopy and enzymatic methods

1. High-energy phosphate compounds were measured in the lateral red and epaxial white muscles of goldfish by: (1) in vivo31P-NMR spectroscopy; (2) in vitro31P-NMR spectroscopy of excised tissue; (3) in vitro31P-NMR spectroscopy of perchloric acid extracts and (4) enzymatic analysis of perchloric acid extracts. 2. A rapid breakdown of phosphocreatine and accumulation of inorganic phosphate was observed during handling, tissue excision and extraction. 3. The lability of phosphocreatine may explain the well-known differences between in vivo NMR spectra and spectra of perchloric acid extracts. 4. A modified procedure is described for extraction of frozen tissue samples, resulting in 100% yield of phosphocreatine, ATP and inorganic phosphate, as judged by the recovery of internal standards.