1. To investigate the transport of potassium on the glutamate uptake carrier, the glutamate uptake current in isolated retinal Müller cells was monitored by whole‐cell clamping, while measuring changes of potassium concentration outside the cells ((K+)o) with an ion‐sensitive microelectrode. 2. Activating glutamate uptake led to an accumulation of potassium outside the cells, consistent with the hypothesis, based on less direct evidence, that the glutamate uptake carrier transports potassium out of the cell. 3. The glutamate‐evoked rise of (K+)o showed the pharmacology and sodium dependence of glutamate uptake. 4. The rise in (K+)o was proportional to the uptake current flowing between 0 and ‐80 mV, implying that the ratio of K+ transported to charge transported by the uptake carrier is constant over this voltage range. The K+ to charge transport ratio was the same for uptake of D‐aspartate and L‐glutamate. 5. By clamping cells with pipettes containing solutions of different (K+), the dependence of the glutamate and aspartate uptake currents on intracellular (K+) was determined. L‐ and D‐aspartate transport showed a smaller maximum uptake current (Imax), and a smaller apparent Michaelis constant (Km) for activation by intracellular K+, than did L‐glutamate transport. The ratio of Imax to Km was the same for these three analogues, a result which can be predicted from simple models of the carrier's operation. 6. Fully activating glutamate uptake in Müller cells in the intact retina would produce a K+ load into the extracellular space of about 0.6 mM s‐1. Suppression of glutamate release from photoreceptors by light will reduce K+ efflux from Müller cells in the outer retina; this may contribute to the light‐evoked fall of (K+)o observed in the outer retina, and thus contribute to shaping the electroretinogram.
The Journal of Physiology – Wiley
Published: Sep 15, 1994
It’s your single place to instantly
discover and read the research
that matters to you.
Enjoy affordable access to
over 18 million articles from more than
15,000 peer-reviewed journals.
All for just $49/month
Query the DeepDyve database, plus search all of PubMed and Google Scholar seamlessly
Save any article or search result from DeepDyve, PubMed, and Google Scholar... all in one place.
Get unlimited, online access to over 18 million full-text articles from more than 15,000 scientific journals.
Read from thousands of the leading scholarly journals from SpringerNature, Elsevier, Wiley-Blackwell, Oxford University Press and more.
All the latest content is available, no embargo periods.
“Hi guys, I cannot tell you how much I love this resource. Incredible. I really believe you've hit the nail on the head with this site in regards to solving the research-purchase issue.”Daniel C.
“Whoa! It’s like Spotify but for academic articles.”@Phil_Robichaud
“I must say, @deepdyve is a fabulous solution to the independent researcher's problem of #access to #information.”@deepthiw
“My last article couldn't be possible without the platform @deepdyve that makes journal papers cheaper.”@JoseServera