Glycolytic enzymes of human fetal and neonatal intraocular fluids.

The levels of the glycolytic enzymes, phosphohexose isomerase, aldolase and LDH and its isozymes, were ascertained in the aqueous of human stillbirths and premature neonate dead (19-24 weeks gestation) and compared with those of older neonates (28-41 weeks) of low survival due mainly to respiratory failure. The fetal aqueous displayed a much greater LDH-P level (mean mU/ml +/- SEM: 45,600 +/- 2550; 72 eyes) in contrast to the near-term infant value (2420 +/- 615; 27 eyes) and 8-20 times higher aldolase and phosphohexose isomerase levels. LDH-P of the fetal vitreous was much lower (5820 +/- 860 mU/ml; 25 eyes) and for lens employed as a filtered homogenate in saline (1:20), amounted to 52.2 +/- 4.2 mU/mg lens (24 eyes). The distribution of LDH isozymes in the fetal vitreous and lens homogenate and the near-term neonate aqueous as determined by polyacrylamide disc electrophoresis, was similar to that of the fetal aqueous, LDH-1 and LDH-5 being least and LDH-3 and LDH-4, the highest. A few small but significant differences were apparent as compared to the fetal aqueous isozymes and included decrements in vitreous LDH-4, lens LDH-3 and neonatal aqueous LDH-3 and increases in vitreous LDH-2 and near-term aqueous LDH-4. The current findings may have application to retinoblastoma for which higher aqueous LDH levels have been reported and employed as a diagnostic adjunct. However, the fetal aqueous LDH values far exceed those encountered in this embryonal-type tumour.