The metabolism of xylose by the ocular lens of the rat

Abstract

The lens of a 28- to 32-day-old rat fed on a 30% xylose diet shows an initial decline in the activity of the hexose monophosphate shunt as reflected by the C-1/C-6 ratio of C14O2 recovered from lenses incubated with [1-C14]-glucose or [6-C14]glucose. This C-1/C-6 ratio returns to normal amounts after the animal has been on the xylose diet for 15-16 days. The TPNH/TPN ratio in these lenses shows a parallel decline and recovery whereas the DPNH/DPN ratio remains unimpaired. Both DPN-and TPN-xylitol dehydrogenases are present in the lenses of control and xylose-fed rats, as previously reported by van Heyningen (1959). There is no significant alteration in their activities in the lenses from xylose-fed rats. The amount of soluble protein in the lenses of xylose-fed rats suggests an inhibition of soluble protein synthesis in these organs after 6-8 days on the diet, with a slow recovery beginning at 14 days. There is a moderate decline of adenosine triphosphate in these lenses after 4 days on the diet with a recovery occurring by 16 days. A hypothesis has been proposed to explain the biochemical changes that occur in these lenses during the period of development and apparent regression of lenticular opacities.