Effect of hypoxemia and hyperglycemia on pH in the intact cat retina.
OBJECTIVE
To examine the effects of acute hypoxemia and hyperglycemia on retinal pH to understand hyperglycemia-induced changes in the normal intact cat retina.


METHODS
Spatial profiles of extracellular hydrogen ion (H+) concentration were obtained from the cat retina, in vivo, using pH-sensitive microelectrodes during normoxia (arterial partial pressure of oxygen [PaO2] = 114.5 +/- 7.9 mm Hg), normoglycemia (plasma glucose concentration, 117 +/- 19 mg/dL), acute hypoxemia (PaO2 = 29.5 +/- 2.2 mm Hg), and acute hyperglycemia (plasma glucose concentration, 303 +/- 67 mg/dL). An H+ diffusion model was fitted to the outer retinal data to quantify photoreceptor H+ production. The inner retinal pH was also examined.


RESULTS
Hypoxemia induced a mean acute panretinal acidification of 0.16 pH units that originated from a 2.55-fold increase in net photoreceptor H+ production. Hyperglycemia induced an acute panretinal acidification of 0.12 pH units; however, photoreceptor H+ production levels remained unchanged. Retinal pH changes followed the course of arterial PaO2 and blood glucose changes.


CONCLUSIONS
The increase in photoreceptor H+ production during hypoxemia confirms the importance of glycolysis in the retina. Hyperglycemia-induced pH changes resulted from either increased inner retinal H+ production or decreased H+ clearance/neutralization. Clinical Relevance The hyperglycemia-induced acidification that originates in the inner retina suggests that retinal acidosis may contribute to the development of diabetic retinal disease.
Padnick-Silver
Lissa
L
Department of Biomedical Engineering, Northwestern University, Evanston, Ill 60208-3107, USA.
Linsenmeier
Robert A
RA
D000138:Acidosis / Q000378:metabolism; D000208:Acute Disease; D000818:Animals; D002415:Cats; D004596:Electroretinography; D006019:Glycolysis; D006863:Hydrogen-Ion Concentration; D006943:Hyperglycemia / Q000378:metabolism*; D000860:Hypoxia / Q000378:metabolism*; D017736:Ion-Selective Electrodes; D008297:Male; D008839:Microelectrodes; D010100:Oxygen / Q000378:metabolism; D010313:Partial Pressure; D012160:Retina / Q000378:metabolism*
D010100:Oxygen