Voltage and temperature dependence of single K+ channels isolated from canine cardiac sarcoplasmic reticulum

• Published in: Biophysical journal Vol. 65; no. 2; pp. 747 - 754
• Main Authors: Shen, W.K., Rasmusson, R.L., Liu, Q.Y., Crews, A.L., Strauss, H.C.
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Elsevier Inc 01.08.1993; Biophysical Society; The Biophysical Society
• Subjects: Animals; Biological and medical sciences; Cell membranes. Ionic channels. Membrane pores; Cell structures and functions; Dogs; Electric Conductivity; Fundamental and applied biological sciences. Psychology; Heart - physiology; Ion Channel Gating - physiology; Kinetics; Lipid Bilayers; Mathematics; Membrane Potentials; Models, Biological; Molecular and cellular biology; Potassium Channels - physiology; Sarcoplasmic Reticulum - physiology; Thermodynamics; Heart; Fissipedia; Carnivora; Temperature; Potassium ion; Electrophysiology; Environmental factor; Ionic channel; Biological activity; Vertebrata; Mammalia; Sarcoplasmic reticulum; Ionic conductance; Membrane potential; Dog
• ISSN: 0006-3495; 1542-0086
• DOI: 10.1016/S0006-3495(93)81100-7

The temperature and voltage dependence of gating and conductance of sarcoplasmic reticulum K+ channels (S-R K+) isolated from adult canine hearts were studied using the reconstituted bilayer technique. Fusion of vesicles from this preparation frequently resulted in the incorporation of a single channel. Only bilayers into which a single S-R K+ channel had fused were studied. The three conductance states of the channel, fully open (O2), substate conductance (O1), and closed (C) were studied as a function of voltage (-50 to +50 mV) and temperature (16 to 37 degrees C). Permeation through the O1 state showed the same temperature dependence as the O2 state corresponding to an enthalpy of permeation of 4.1–4.2 kcal/mol, which is similar to that for K+ diffusion through water. As expected, increased temperature increased the frequency of gating transitions and shortened the average dwell time spent in any conductance state. Over the range of 25 to 37 degrees C, the average dwell time spent in the O1, O2, and C states decreased by 44 +/- 11, 36 +/- 13, and 78 +/- 7% (n = 3 to 4 channels), respectively. The ratio of probabilities between the various conductance states was not strongly temperature sensitive. Analysis of the voltage dependence of this channel was carried out at 37 degrees C and revealed that the dwell times of the O1 and O2 states were voltage insensitive and the probability ratio (PO2:PO1) was approximately 7 and was voltage insensitive.