Retinal arterial occlusion leads to acidosis in the cat

This study investigated the changes in pH during retinal artery occlusion by means of extracellular H+ concentration ([H+]o) measurements in the retina under both air and 100% O2 ventilation. Occlusion was produced in intact anesthetised cats by pressing with a probe onto a retinal artery. [H+]o profiles were recorded across the retina with pH sensitive microelectrodes. The average inner retinal [H+]o increased during occlusion, resulting in an acidification of as much as 0.10 pH units, even under 100% O2 ventilation. The inner retinal H+ profile magnitude decreased during occlusion due to impaired clearance. The average outer retinal H+ profile magnitude also increased even though outer retinal H+ production did not increase during occlusion. This might be due to H+ diffusion from the inner retina to the outer retina, which is opposite to the flux in the normal retina. After reperfusion, [H+]o returned to its preocclusion value. In conclusion, arterial occlusion leads to acidification of the retina. Enhanced oxygenation during occlusion did not decrease this acidification. This may explain why increasing PO2 in the retina by enhanced O2 breathing improves retinal function during and after occlusion, but does not totally reverse the effect of occlusion.