The pentose phosphate pathway in developing chick cornea.

Abstract

Embryonic chick corneas at different stages of development were evaluated for activity of the pentose phosphate pathway. The appearance of activity was concurrent with the onset of corneal transperancy (stage 40). Highest values were found after complete transparency is achieved (stage 45 and after hatching). Phenazine methosulfate, an artificial electron acceptor, increased activity at all stages studied even before endogenous activity was measurable; however, no increase in glucose uptake was observed. Thus, the enzymes for the pathway are present at early stages (i.e., stage 38 and 40) although in latent form. The pathway probably functions in the developing cornea to generate NADPH rather than sugar moieties for macromolecular incorporation.