Retinal pigment epithelium (RPE) was isolated from human donors with no known eye disease and normal-appearing fundi and was grown in culture. Population doubling times were measured for fifth passage RPE cells; the mean was 2.25+/-0.75 days and showed a correlation with the age of the donor. Metabolic studies were performed by perfusing the cells with 1-[13C]-D-glucose and monitoring the perfusate with magnetic resonance spectroscopy. Glucose uptake was 10.5+/-3.3 nmoles/min/mg protein. Lactate production from glucose was 20.0+/-5.00 nmoles/min/mg protein. The percentage of glucose through the hexose monophosphate shunt was 21+/-2%. Oxygen (O) consumption was measured at 20.1+/-4.1 nmoles O/min/mg endogenous and 14.5+/-4.8 nmoles O/min/mg with 10 mM glucose. These cells exhibit high rates of lactate production concomitantly with high oxygen consumptions and high flux through the hexose monophosphate shunt.