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To the Editor:
—In reply to Dr. Kinoshita's comments on my recent article ("Carbohydrate Metabolism in the Rat Lens as Related to the Age of the Animal," Arch. Ophthal. 65:181, 1961), I would certainly agree with him that the TPNH/TPN ratio does not necessarily reflect the activity of the hexose monophosphate shunt. However, what I had intended to indicate was that this ratio taken in context with the C1C6 ratio and an active G-6-P dehydrogenase system might indicate the presence of an active shunt pathway in the young rat lens. As Dr. Kinoshita has pointed out, the presence of relatively large amounts of total TPN in this organ is also a significant indicator for the presence of such a pathway of glucose oxidation.With respect to Dr. Kinoshita's comment regarding the drop in C-1 oxidation of glucose with age, he states that this is not surprising since
Lerman S. THE AGING RAT LENS-Reply. Arch Ophthalmol. 1961;66(3):448-449. doi:10.1001/archopht.1961.00960010449024