Indomethacin lowers optic nerve oxygen tension and reduces the effect of carbonic anhydrase inhibition and carbon dioxide breathing.
OBJECTIVE
Prostaglandins are important in blood flow regulation. Carbon dioxide (CO(2)) breathing and carbonic anhydrase inhibition increase the oxygen tension in the retina and optic nerve. To study the mechanism of this effect and the role of cyclo-oxygenase in the regulation of optic nerve oxygen tension (ONPO(2)), the authors investigated how indomethacin affects ONPO(2) and the ONPO(2) increases caused by CO(2) breathing and carbonic anhydrase inhibition in the pig.


METHODS
Optic nerve oxygen tension was measured in 11 pigs with a polarographic oxygen electrode. The tip of the electrode was placed 0.5 mm above the optic disc. The effects of indomethacin, CO(2) breathing (3%) before and after indomethacin treatment, and carbonic anhydrase inhibition with or without indomethacin treatment were investigated.


RESULTS
Administration of 300 mg indomethacin decreased optic nerve oxygen tension significantly. Carbonic anhydrase inhibition and CO(2) breathing increased ONPO(2) significantly. After indomethacin had been given, the rise in ONPO(2) caused by CO(2) breathing and carbonic anhydrase inhibition was significantly reduced.


CONCLUSIONS
Systemic administration of indomethacin decreases the optic nerve oxygen tension; this is probably the result of decreased blood flow through vasoconstriction of vessels in the optic nerve. Additionally, indomethacin diminishes the ONPO(2) increasing effect of CO(2) breathing and carbonic anhydrase inhibition, thus affecting the reactivity of vessels in the optic nerve.
Pedersen
D B
DB
Department of Ophthalmology, 2061, Rigshospitalet, Blegdamsvej 9, 2100 Copenhagen Ø, Denmark. daniella@dadlnet.dk
Eysteinsson
T
T
Stefánsson
E
E
Kiilgaard
J F
JF
La Cour
M
M
Bang
K
K
Jensen
P K
PK
D000818:Animals; D002245:Carbon Dioxide / Q000502:physiology*; D002257:Carbonic Anhydrase Inhibitors / Q000378:metabolism*; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology*; D007213:Indomethacin / Q000494:pharmacology*; D009900:Optic Nerve / Q000187:drug effects* / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism*; D013552:Swine
D002257:Carbonic Anhydrase Inhibitors; D016861:Cyclooxygenase Inhibitors; D002245:Carbon Dioxide; D010100:Oxygen; D007213:Indomethacin