Single cells from the bullfrog (Rana catesbeiana) atrium have been prepared by using a modification of the enzymatic dispersion procedure described by Bagby et al. (1971. Nature [Long.]. 234:351--352) and Fay and Delise (1973. Proc. Natl. Acad. Sci. U.S.A. 70:641--645). Visualization of relaxed cells via phase-contrast or Nomarski optics (magnification, 400--600) indicates that cells range between 150 and 350 micrometers in length and 4 and 7 micrometers in diameter. The mean sarcomere length in relaxed, quiescent atrial cells in 2.05 micrometer. Conventional electrophysiological measurements have been made. In normal Ringer's solution (2.5 mM K+, 2.5 mM Ca++) acceptable cells have stable resting potentials of about -88 mV, and large (125 mV) long-duration (approximately 720 ms) action potentials can be elicited. The Vm vs. log[K+]0 relation obtained from isolated cells is similar to that of the intact atrium. The depolarizing phase of the action potential of isolated atrial myocytes exhibits two pharmacologically separable components: tetrodotoxin (10(-6) g/ml) markedly suppresses the initial regenerative depolarization, whereas verapamil (3 x 10(-6) M) inhibits the secondary depolarization and reduce the plateau height. A bridge circuit was used to estimate the input resistance (220 +/- 7 M omega) and time constant 20 +/- 7 ms) of these cells. Two-microelectrode experiments have revealed small differences in the electrotonic potentials recorded simultaneously at two different sites within a single cell. The equations for a linear, short cable were used to calculate the electrical constants of relaxed, single atrial cells: lambda = 921.3 +/- 29.5 micrometers; Ri = 118.1 +/- 24.5 omega cm; Rm = 7.9 +/- 1.2 x 10(3) omega cm2; Cm = 2.2 +/- 0.3 mu Fcm-2. These results and the atrial cell morphology suggest that this preparation may be particularly suitable for voltage-clamp studies.
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1 July 1981
Article|
July 01 1981
Active and passive electrical properties of single bullfrog atrial cells.
J R Hume
W Giles
Online ISSN: 1540-7748
Print ISSN: 0022-1295
J Gen Physiol (1981) 78 (1): 19–42.
Citation
J R Hume, W Giles; Active and passive electrical properties of single bullfrog atrial cells.. J Gen Physiol 1 July 1981; 78 (1): 19–42. doi: https://doi.org/10.1085/jgp.78.1.19
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