Measurement and manipulation of the partial pressure of oxygen in the rat anterior chamber.

Abstract

To measure the partial pressure of oxygen in the anterior chamber of the rat eye under a variety of physiological conditions. Polarographic oxygen electrode measurements were made in methoxyflurane-anesthetized Wistar or Sprague-Dawley rats. After ketamine-xylazine or pentobarbital induction, animals were artificially ventilated with a variety of gas mixtures; gases were directed over the corneal surface during measurement of the partial pressure of oxygen in the middle of the pupil at the surface of the lens. The partial pressure of oxygen in the anterior chamber of the rat eye was measured as 63 +/- 9 mm Hg (mean +/- S.D. ). Breathing 100% oxygen and delivery of 100% oxygen to the cornea additively increased aqueous humor oxygen partial pressure to levels above 279 +/- 45 mm Hg with the greatest increase coming from inhaled 100% oxygen. Conversely, inhalation and subsequent transcorneal delivery of 10% oxygen reduced levels to 22 +/- 11 mm Hg. These results suggest that the partial pressure of oxygen in the anterior chamber is sensitive to the environment in contact with the cornea. In the rat eye, the delivery of oxygen to the anterior chamber via transcorneal diffusion may be more significant than for larger animals.