{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,16]],"date-time":"2026-07-16T17:57:38Z","timestamp":1784224658469,"version":"3.55.0"},"reference-count":0,"publisher":"Wiley","issue":"1","license":[{"start":{"date-parts":[[1978,1,1]],"date-time":"1978-01-01T00:00:00Z","timestamp":252460800000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/onlinelibrary.wiley.com\/termsAndConditions#vor"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["The Journal of Physiology"],"published-print":{"date-parts":[[1978,1]]},"abstract":"1. Outward currents in cat ventricular fibres have been studied using the single sucrose gap method. The time dependent outward currents can be separated into a fast component, I<\/jats:italic>K<\/jats:sub>, and a slow component, I<\/jats:italic>x<\/jats:sub>. The voltage dependence of the I<\/jats:italic>K<\/jats:sub> time constant was bell\u2010shaped, being about 150 msec at \u201090 mV, 500 msec at \u201025 mV and 300 msec at +30 mV. The combination of much faster time constants and larger amplitudes relative to I<\/jats:italic>x<\/jats:sub> allowed the estimation of I<\/jats:italic>K<\/jats:sub> amplitude, but not time course, from semilog plots of membrane currents accompanying 2 sec depolarizations.<\/jats:p>2. The \u2018steady\u2010state\u2019 outward current at 2 sec (I<\/jats:italic>ss<\/jats:sub>) was separated into time independent background current (I<\/jats:italic>bg<\/jats:sub>) and time dependent I<\/jats:italic>K<\/jats:sub>. The activation threshold for I<\/jats:italic>K<\/jats:sub> was about \u201050 mV and its amplitude increased steeply between \u201030 and +10 mV. The ratio of I<\/jats:italic>bg<\/jats:sub> to I<\/jats:italic>K<\/jats:sub> was about 1 between \u201030 and +30 mV.<\/jats:p>3. The current\u2014voltage relations of I<\/jats:italic>ss<\/jats:sub> and I<\/jats:italic>bg<\/jats:sub> showed inward going rectification but negative slope regions were not observed. Raising the external K concentration from 3 to 10, 20 and 30 m\nM<\/jats:sc> increased conductance and induced \u2018cross\u2010overs\u2019 in the current\u2014voltage relations. Increases in conductance were offset by the reductions in driving force, i.e. currents at plateau potentials were not larger in high K solutions.<\/jats:p>4. K accumulation occurs in response to prolonged membrane depolarization but conductance rather than accumulation appears to be responsible for the slowly rising outward current, I<\/jats:italic>x<\/jats:sub>. However, the accumulation which takes place during the activation of I<\/jats:italic>x<\/jats:sub> may preclude an accurate determination of its time course and reversal potential.<\/jats:p>5. The potential at which outward I<\/jats:italic>K<\/jats:sub> tails declined to zero was strongly dependent on external K concentration in the range 3\u201030 m\nM<\/jats:sc>. Inward going I<\/jats:italic>K<\/jats:sub> tails were difficult to detect because control hyperpolarization from the resting potential triggered large inward time dependent currents. Evidence is presented suggesting that much of this time dependency is due to the depletion of extracellular K from regions of restricted diffusion.<\/jats:p>6. The steady\u2010state activation variable (n<\/jats:italic>\u221e<\/jats:sub>) of the I<\/jats:italic>K<\/jats:sub>\u2010system had to be calculated from isochronic (300 msec activating pulses) activation relations and \u03c4n<\/jats:sub>s because shifts in V<\/jats:italic>K<\/jats:sub> due to K accumulation precluded complete activations. The shape of n<\/jats:italic>\u221e<\/jats:sub> was sigmoid approaching 0 at \u201060 mV, 0\u00b75 at \u201020 mV and 1 at +20 mV.<\/jats:p>7. The fully activated current\u2014voltage relation of I<\/jats:italic>K<\/jats:sub> displayed inward going rectification.<\/jats:p>8. It is concluded that there are strong similarities between I<\/jats:italic>K<\/jats:sub> in ventricular muscle and i<\/jats:italic>x1<\/jats:sub> in Purkinje fibres. Possible counterparts in frog atrial muscle include the currents labelled I<\/jats:italic>1<\/jats:sub> and i<\/jats:italic>x.slow<\/jats:sub>.<\/jats:p>","DOI":"10.1113\/jphysiol.1978.sp012144","type":"journal-article","created":{"date-parts":[[2014,12,19]],"date-time":"2014-12-19T08:06:47Z","timestamp":1418976407000},"page":"217-246","source":"Crossref","is-referenced-by-count":62,"title":["THE POTASSIUM CURRENT UNDERLYING DELAYED RECTIFICATION IN CAT VENTRICULAR MUSCLE"],"prefix":"10.1113","volume":"274","author":[{"given":"T. F.","family":"McDonald","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"W.","family":"Trautwein","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"311","published-online":{"date-parts":[[1978,1]]},"container-title":["The Journal of Physiology"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/api.wiley.com\/onlinelibrary\/tdm\/v1\/articles\/10.1113%2Fjphysiol.1978.sp012144","content-type":"unspecified","content-version":"vor","intended-application":"text-mining"},{"URL":"https:\/\/physoc.onlinelibrary.wiley.com\/doi\/pdf\/10.1113\/jphysiol.1978.sp012144","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2023,11,5]],"date-time":"2023-11-05T15:49:36Z","timestamp":1699199376000},"score":1,"resource":{"primary":{"URL":"https:\/\/physoc.onlinelibrary.wiley.com\/doi\/10.1113\/jphysiol.1978.sp012144"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[1978,1]]},"references-count":0,"journal-issue":{"issue":"1","published-print":{"date-parts":[[1978,1]]}},"alternative-id":["10.1113\/jphysiol.1978.sp012144"],"URL":"https:\/\/doi.org\/10.1113\/jphysiol.1978.sp012144","archive":["Portico"],"relation":{},"ISSN":["0022-3751","1469-7793"],"issn-type":[{"value":"0022-3751","type":"print"},{"value":"1469-7793","type":"electronic"}],"subject":[],"published":{"date-parts":[[1978,1]]}}}