K channels of bovine adrenal chromaffin cells were studied using patch‐clamp techniques. Whole‐cell K currents measured near +10 mV were much larger in 1 mM‐external Ca than in Ca‐free saline. Noise analysis suggested that this Ca‐dependent current was carried by a large unitary conductance channel, called BK channel, which was previously described in inside‐out patches (Marty, 1981). The Ca‐dependent K current near +10 mV declined with time due to 'run‐down' of Ca channels. At the same time, a fraction of the outward current observed above +50 mV was also eliminated. This outward current component probably represents K efflux through Ca channels. Whole‐cell Ca‐dependent K currents were studied using various Ca buffers. EGTA buffers were surprisingly inefficient: in order to block the current entirely, it was necessary to use an isotonic EGTA solution and to increase internal pH. 1,2‐bis(o‐aminophenoxy)ethane‐N,N,N',N'‐tetraacetic acid (BAPTA) was at least five times more efficient than EGTA. In isolated patches three types of single‐channel K currents were observed. Under normal ionic conditions (140 mM‐K inside, 140 mM‐Na outside), the unitary conductances measured between ‐20 and +40 mV were 96 pS, 18 pS and 8 pS. The 96 pS channels are the Ca‐dependent BK channels. 18 pS and 8 pS channels were both activated and then inactivated by membrane depolarization. Both displayed complex kinetics; single‐channel currents were grouped in bursts. Activation and inactivation kinetics were faster for the 18 pS channel (therefore termed FK channel, for fast K channel) than for the 8 pS channel (SK channel, for slow or small amplitude channel). The voltage dependence of opening probability was steeper for the FK channel as compared to the SK channel.
The Journal of Physiology – Wiley
Published: Oct 1, 1985
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