In squid axons, internally applied ATP potentiates the magnitude of the potassium conductance and slows down its activation kinetics. This effect was characterized using internally dialyzed axons under voltage-clamp conditions. Both amplitude potentiation and kinetic slow-down effects are very selective towards ATP, other nucleotides like GTP and ITP are ineffective in millimolar concentrations. The current potentiation Km for ATP is near 10 microM with no further effects for concentrations greater than 100 microM. ATP effect is most likely produced via a phosphorylative reaction because Mg ion is an obligatory requirement and nonhydrolyzable ATP analogues are without effect. In the presence of ATP, the K current presents more delay, resembling a Cole-Moore effect due to local hyperpolarization of the channel. ATP effect induces a 10-20 mV shift in both activation and inactivation parameters towards more depolarized potentials. As a consequence of this shift, conductance-voltage curves with and without ATP cross at approximately -40 mV. This result is consistent with the hyperpolarization observed with ATP depletion, which is reversed by ATP addition. At potentials around the resting value, addition of ATP removes almost completely K current slow inactivation. It is suggested that a change in the amount of the slow inactivation is responsible for the differences in current amplitude with and without ATP, possibly as a consequence of the additional negative charge carried by the phosphate group. However, a modification of the local potential is not enough to explain completely the differences under the two conditions.
The Journal of General Physiology – Rockefeller University Press
Published: Jun 1, 1989
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