Interspecies analysis of corneal phosphate metabolites

Phosphate metabolite profiles of corneas were determined for human, baboon, monkey, cat, guinea-pig, pig, dog, rabbit, and cow using 31P-nuclear magnetic resonance (NMR) spectroscopy. Metabolites quantitatively measured included the low-energy metabolites: hexose 6-phosphates, alpha-glycerophosphate, unassigned phosphorus compound(s) at 4.26-3.91 delta, ethanolamine phosphate, nucleoside monophosphates, choline phosphate, inorganic orthophosphate, phosphodiesters (glycerol 3-phosphoethanolamine and glycerol 3-phosphocholine), and the high-energy metabolites: phosphocreatine, adenosine triphosphate (ATP), adenosine diphosphate (ADP), nucleoside diphosphosugars and dinucleotides. The number of significant differences in metabolites among the species studied, relative to humans, increased in the following order: baboon less than monkey approximately pig approximately cow less than cat approximately guinea-pig less than rabbit less than dog. The 31P energy modulus (human, 1.3 +/- 0.20 S.D.). ATP:Pi ratio (human, 0.5 +/- 0.05 S.D.). ATP:ADP ratio (human, 0.38 +/- 0.34 S.D.). ATP:ADP plus Pi ratio (human, 0.43 +/- 0.04 S.D.) and SP:Pi ratio (human, 0.37 +/- 0.04 S.D.) were determined for each species. All these ratios are indicators of corneal metabolic status, and their values suggest that, of the common laboratory research animals examined, the baboon and monkey are the most like man, and the rabbit and cow the least like man.