Changes in the energy metabolism of cultured lens epithelial cells in comparison with the fresh lens.
Energy metabolism of bovine cultured lens epithelial cells (CLEC) was compared to that of fresh bovine lens. CLEC contained high levels of ATP (44 nmol mg protein-1) and creatine phosphate (13 nmol mg protein-1). An ATP/ADP ratio of ten and a creatine phosphate/creatine ratio of two indicated the cells were in a well-energized state. ATP concentration in fresh epithelium was comparable to that of CLEC; however in the anterior cortex it was tenfold lower. In contrast to fresh lenses, CLEC were able to oxidize glucose, lactate and palmitic acid. Lactate was oxidized at the highest rate. In CLEC, 42% of the ATP generated by catabolizing glucose resulted from oxidative phosphorylation. Glucose (5 mM) was degraded to lactate and CO2 at a 2:1 ratio. The hexose monophosphate pathway accounted for two thirds of the CO2 produced. In the fresh whole bovine lens palmitate was not oxidized and lactate was oxidized to a lesser degree than in CLEC. Only one-tenth of the ATP generated by glucose catabolism in the fresh whole lens was derived from oxidative phosphorylation. This was also the case for a preparation of fresh epithelium, maintained in air and 100% oxygen, demonstrating that the preferential glycolytic catabolism of glucose in lens is not caused by limited oxygen diffusion. In the fresh bovine lens the epithelium accounted for one third of the glucose catabolism of the whole lens, even though it had only about 0.1% of its protein mass. In fresh human lenses, conversion of glucose into lactate was even more pronounced--the lactate/CO2 ratio was 73:1.(ABSTRACT TRUNCATED AT 250 WORDS)
Piper
H M
HM
Physiologisches Institut I, Universität Düsseldorf, F.R.G.
Spahr
R
R
Krützfeldt
A
A
Siegmund
B
B
Schwartz
P
P
Pau
H
H
D000255:Adenosine Triphosphate / Q000378:metabolism; D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D002245:Carbon Dioxide / Q000378:metabolism; D002417:Cattle; D002478:Cells, Cultured; D004734:Energy Metabolism; D004848:Epithelium / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D006801:Humans; D007773:Lactates / Q000378:metabolism; D007903:Lens Capsule, Crystalline / Q000378:metabolism*; D007908:Lens, Crystalline / Q000378:metabolism*
D007773:Lactates; D002245:Carbon Dioxide; D000255:Adenosine Triphosphate; D005947:Glucose