title: Light-induced pH changes in the intact retinae of normal and early diabetic rats.
abstract: Double-barreled H(+)-selective microelectrodes were used to measure local extracellular concentration of H(+) ([H(+)]o) in the retina of dark-adapted anesthetized Long-Evans rats. The microelectrode advanced in steps of 30 μm throughout the retina from the vitreal surface to retinal pigment epithelium and then to the choroid, recording changes in [H(+)]o evoked by light stimulation. Recordings were performed in diabetic rats 1-3 months after intraperitoneal injection of streptozotocin and the results were compared with data obtained in age-matched control animals. Brief light stimulation (2.5 s) evoked changes of [H(+)]o with amplitudes of a few nM. Throughout the retina, there was a transient initial acidification for ∼200 ms followed by steady alkalinization, although amplitudes and kinetics of these components were slightly variable in different retinal layers. No significant difference was found when the light-induced [H(+)]o changes recorded in various retinal layers of early diabetic rats were compared with the [H(+)]o changes from corresponding layers of control animals. Also, when H(+)-selective microelectrodes were located in the retinal pigment epithelium (RPE) layer, an increase in H(+) was recorded, whose time course and amplitude were similar in control and diabetic rats. However, a striking difference between light-induced [H(+)]o changes in controls and diabetics was observed in the choriocapillaris, in the thin layer (10-20 μm) distal to the basal membrane of the RPE. In control rats, choroidal [H(+)]o decreased in a few cases, but much more often practically did not change. In contrast, diabetic rats demonstrated either an increase (in half of the cases) or no change in choroidal [H(+)]o. The data suggest that the active participation of the choroidal blood supply in stabilization of [H(+)]o could be partially compromised already at early stages of diabetes in rats. Interestingly, it appeared that the acid removal by the choroidal circulation was compromised most after 1 month of diabetes and tended to improve later.
authors.affiliation: Department of Biomedical Engineering, 2145 Sheridan Road, Northwestern University, Evanston, IL 60208-3107, United States. Electronic address: andrey.dmitriev@northwestern.edu.
authors.forename: Andrey V
authors.initials: AV
authors.lastname: Dmitriev
authors.affiliation: Department of Biomedical Engineering, 2145 Sheridan Road, Northwestern University, Evanston, IL 60208-3107, United States. Electronic address: d-henderson@northwestern.edu.
authors.forename: Desmond
authors.initials: D
authors.lastname: Henderson
authors.affiliation: Department of Biomedical Engineering, 2145 Sheridan Road, Northwestern University, Evanston, IL 60208-3107, United States; Department of Neurobiology, 2205 Tech Drive, Northwestern University, Evanston, IL 60208, United States; Department of Ophthalmology, Northwestern University, 645 North Michigan Avenue, Suite 440, Chicago, IL 60611, United States. Electronic address: r-linsenmeier@northwestern.edu.
authors.forename: Robert A
authors.initials: RA
authors.lastname: Linsenmeier
mesh_terms: D000818:Animals; D003623:Dark Adaptation / Q000502:physiology*; D003921:Diabetes Mellitus, Experimental; D003930:Diabetic Retinopathy / Q000175:diagnosis / Q000378:metabolism*; D004596:Electroretinography; D006863:Hydrogen-Ion Concentration; D008297:Male; D008839:Microelectrodes; D010775:Photic Stimulation; D051381:Rats; D020318:Rats, Long-Evans; D012165:Retinal Ganglion Cells / Q000378:metabolism* / Q000473:pathology; D013997:Time Factors
keywords: Choroidal blood supply; Diabetes; Ion-selective microelectrodes; Rat; Retina; Retinal pigment epithelium; Streptozotocin; pH