Comparison of phosphate metabolites of the ocular humors

Ocular humors (aqueous humor and vitreous body) were obtained from porcine eyes. Perchloric acid extracts were prepared from aqueous and vitreous aspirates, and phosphorus-31 nuclear magnetic resonance spectroscopy 31P-NMR performed. Resonance signals from four high-energy phosphate groups (phosphocreatine, adenosine tri- and diphosphate and the dinucleotides) and nine low-energy phosphate groups [dihydroxyacetone phosphate, hexose-6-phosphate, alpha-glycerophosphate, fructose-1,6-diphosphate, ethanolamine phosphate, choline phosphate, inorganic orthophosphate (Pi), glycerol-3-phosphorylethanolamine and glycerol-3-phosphorylcholine] were present in the aqueous humor and/or vitreous body. Vitreous body phosphates significantly elevated relative to that of the aqueous humor were: DHAP, Hex 6-P, alpha-GP, Fru 1,6-diP, CP, GPE, PCr, ATP, ADP, and the dinucleotides; only Pi was significantly lower. Six metabolic indices (monoesters, diesters, monoesters/diesters, monoesters/Pi, ATP/Pi, energy modulus) were determined; all vitreous body indices were significantly higher than those of the aqueous humor. In particular, the energy modulus, a measure of overall metabolic energy status, was higher in the vitreous body (0.121 +/- 0.047) than in the aqueous humor (0.05 +/- 0.021).