Comparative studies of glucose metabolism in corneas of the dogfish shark, longhorn sculpin and rainbow trout

Abstract

Oxygen consumption, glucose oxidation, and specific activities of representative enzymes of glycolysis, the hexose-monophosphate shunt (HMS), and the tricarboxylic acid cycle (TCA) were measured in corneas of the dogfish shark, longhorn sculpin and rainbow trout. These three pathways of glucose metabolism are present in corneas of each of these species. The non-swelling cornea of the dogfish shark was found to have the lowest rate of glucose oxidation with relatively high HMS activity. Corneas of the marine and fresh water teleosts oxidize glucose at higher rates with less glucose diverted into the HMS pathway. Glucose metabolism in the elasmobranch cornea provides for cell division, maintenance and repair in this tissue. The metabolic requirements of these anabolic processes are largely fulfilled by HMS glucose oxidation. In the teleost cornea in addition to these functions, glucose metabolism also serves to fuel the energy dependent transport processes involved in the maintenance of corneal transparency. The glycolytic and tricarboxylic acid pathways are of particular importance in producing the ATP energy for these transport processes.