Effects of intravenous iodoacetate and iodate on pH outside rod photoreceptors in the cat retina.
OBJECTIVE
Effects of intravenous iodoacetate (a glycolysis inhibitor) and iodate (a metabolism inhibitor selective to retinal pigment epithelium) on light-evoked alkalinizations and hypoxia-induced acidifications were studied in the dark-adapted cat retina, in vivo, to learn about pH regulation.


METHODS
pH was recorded in the extracellular space surrounding rod photoreceptors with double-barrelled H(+)-selective microelectrodes.


RESULTS
Intravenous infusion of 5 mg/kg iodoacetate-induced alkalinizations in the outer nuclear layer and suppressed both light-evoked and hypoxia-induced pH responses immediately. Iodate injection (30 mg/kg) produced acidifications in the subretinal space and affected light-evoked alkalinizations gradually but not hypoxia-induced acidifications.


CONCLUSIONS
These results suggest that rods glycolysis plays an important role in both light-evoked and hypoxia-induced pH responses. And the retinal pigment epithelium may have little concern with light-evoked alkalinizations except that it plays an important role in regenerating the rhodopsin to be needed for the light responses of photoreceptors. Furthermore, the finding of the intravenous-iodoacetate-induced alkalinization in the outer nuclear layer supports that acid production by rods in the dark is originated from glycolysis to support the dark current. The iodate-induced acidification in the subretinal space indicators that the retinal pigment epithelium might actively transport acids from the subretinal space to the choroid.
Department of Ophthalmology, Faculty of Medicine, Kyoto University, Japan.
F
F
Yamamoto
Y
Y
Honda
D000818:Animals; D002415:Cats; D015687:Cell Hypoxia; D003623:Dark Adaptation; D004596:Electroretinography; D006019:Glycolysis; D006863:Hydrogen-Ion Concentration; D007262:Infusions, Intravenous; D007452:Iodates / Q000008:administration & dosage / Q000494:pharmacology*; D007461:Iodoacetates / Q000008:administration & dosage / Q000494:pharmacology*; D019807:Iodoacetic Acid; D010786:Photoreceptor Cells / Q000187:drug effects / Q000502:physiology; D012374:Rod Cell Outer Segment / Q000187:drug effects / Q000502:physiology*
D007452:Iodates; D007461:Iodoacetates; C032285:sodium iodate; D019807:Iodoacetic Acid