ISSN:
1432-1424
Keywords:
atrium
;
sinus venosus
;
pacemaker
;
inward rectifier
;
impedance
;
isolated cardiac cells
;
linear analysis
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
Notes:
Summary Single electrode whole cell voltage-clamp experiments and frequency domain analyses have been used to study and compare the K+ currents in enzymatically dispersed single cells from the atrium and the sinus venosus (pacemaker region) of the bullfrog heart. Admittance measurements made near the ‘resting’ or zero-current potential yield data from which the equivalent circuit of each cell type may be obtained. Data from both atrial and pacemaker cells are well-fitted by a model consisting only of parallel resistance-capacitative elements, as predicted from their micro-anatomy. Neither of these amphibian cardiac cells contain a transverse tubule system (TT) and both have very little sarcoplasmic reticulum (SR). These results complement and extend two earlier investigations: (i) Moore, Schmid and Isenberg (J. Membrane Biol. 81:29–40, 1984) have reported that in guinea pig ventricle cells (whichdo contain an internal membrane system consisting of transverse tubules and a substantial SR) the SR may be electrically coupled to the sarcolemma; (ii) Shibata and Giles (Biophys. J. 45:136a, 1984) have shown that although bullfrog atrial cells have an inwardly rectifying back-ground K+ current, $$I_{K_1 } $$ , pacemaker cells from the immediately adjacent sinus venosus do not. Data from admittance measurements also provide evidence that a TTX-insensitive inward Ca2+ current is activated in the pacemaker range of potentials.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01869709
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