Respiration and Glutathione in the Growing Rat Lens

¹ Department of Anatomy, The University of Michigan, Ann Arbor, Mich.

The oxygen uptake of the postnatal rat lens increases to 1.25 µal per hour at 20 days and then falls abruptly to about half this level. The respiratory activity per unit fresh weight decays in two corresponding cycles from a high of 230 µg per gram-hour at birth. The glutathione concentration meanwhile rises to a maximum of 2.5 µg. per gram at 4 days and then decreases slightly to a constant level. The amount of ascorbic acid in the rat lens proves too small for accurate analysis and cannot also be compared. Glutathione, despite the lack of correlation between its pattern of growth and that of respiration, could still be the major substrate for respiration if factors other than substrate concentration are rate limiting. In this case, glutathione would have a fairly high oxidation-reduction turnover rate, particularly in the youngest lenses. Regression of the hyaloid circulation may figure in the loss of respiring material from the lens after 3 weeks of age.