Effect of elevated glucose concentration on membrane voltage regulation in retinal capillary pericytes.
The influence of elevated glucose concentration on resting membrane voltage, electrogenic Na(+)-K(+)-ATPase, and ATP-sensitive potassium channels (KATP channels) was studied in cultured bovine retinal capillary pericytes using conventional microelectrodes. The resting membrane voltage in cells grown in medium containing 5 mM glucose (control) averaged -27 +/- 1.2 mV (mean +/- SE, n = 26) and was not different from cells grown in medium containing 22.5 mM glucose (-26 1.2 mV, n = 26). Addition of ouabain (10(-4) M), a specific inhibitor of the Na(+)-K(+)-ATPase, depolarized the membrane potential by 3.6 +/- 0.4 mV (n = 10) in cells grown under control conditions and 0.7 +/- 0.2 mV (n = 6) in cells grown under elevated glucose conditions. Thus, electrogenic activity of the Na(+)-K(+)-ATPase was significantly (P < 0.0001) reduced to 19% compared with control conditions. Electrogenic Na(+)-K(+)-ATPase activity could be partially restored (ouabain-induced depolarization delta V = 2.0 +/- 0.2 mV, n = 6) in cells grown with high glucose in the presence of the aldose reductase inhibitor tolrestat (10(-5) M). The potassium channel opener Hoe 234 (10(-6) M) induced membrane potential hyperpolarization in control cells (delta V = 7.3 +/- 1.2 mV, n = 13), which could be completely inhibited by the KATP channel blocker glibenclamide (10(-7) M, n = 5). This indicates that pericytes possess KATP channels. The effect of KATP channels on membrane voltage was not significantly changed (P = 0.16) in cells cultured under high-glucose conditions (delta V = 9.6 +/- 2.0 mV, n = 6).(ABSTRACT TRUNCATED AT 250 WORDS)
Berweck
S
S
Institute of Clinical Physiology, Universitätsklinikum Steglitz, Freie Universität Berlin, Germany.
Thieme
H
H
Helbig
H
H
Lepple-Wienhues
A
A
Wiederholt
M
M
D000818:Animals; D002196:Capillaries / Q000166:cytology / Q000378:metabolism; D002417:Cattle; D002478:Cells, Cultured; D004594:Electrophysiology; D005947:Glucose / Q000378:metabolism*; D008564:Membrane Potentials / Q000502:physiology; D010042:Ouabain / Q000494:pharmacology; D015221:Potassium Channels / Q000378:metabolism*; D012171:Retinal Vessels / Q000166:cytology / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000187:drug effects / Q000378:metabolism*
D015221:Potassium Channels; D010042:Ouabain; D000254:Sodium-Potassium-Exchanging ATPase; D005947:Glucose