Abstract
1. Small re-aggregates of cells dissociated from the ventricles of 12-or 17-day-old chick embryonic hearts have beating properties in low potassium tissue culture medium which differ from re-aggregates prepared from 7-day-old hearts; 12-day preparations either beat with a slower rate than comparable-size 7-day preparations or they are quiescent; 17-day preparations usually do not beat. 2. A two-micro-electrode voltage-clamp technique was used to analyse the membrane currents in these preparations in the -120 to -40 mV potential range. 3. A potassium ion membrane current was measured in 12-day and 17-day preparations which was qualitatively similar to the potassium ion current measured in 7-day preparations (Clay & Shrier, 1981). It differed in that its amplitude was diminished in the ratio 1:0.2:0.03 over the 7-, 12- and 17-day sequence. Furthermore, its maximum time constant was 2 sec at both 12 and 17 days, as compared to 1 sec at 7 days, and its membrane potential range of activation was -80 to -70 mV at 12 and 17 days, as compared to -90 to -60 mV at 7 days. 4. The background current also changed with development, becoming less inward over the 7-, 12- and 17-day sequence. The voltage dependence of this change suggested that it was caused by a developmental decrease of the background sodium current. 5. The change in the background component is primarily responsible for the loss of automaticity over the 7-, 12-, and 17-day sequence.
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Selected References
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- Beeler G. W., Reuter H. Reconstruction of the action potential of ventricular myocardial fibres. J Physiol. 1977 Jun;268(1):177–210. doi: 10.1113/jphysiol.1977.sp011853. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Carmeliet E. E., Horres C. R., Lieberman M., Vereecke J. S. Developmental aspects of potassium flux and permeability of the embryonic chick heart. J Physiol. 1976 Jan;254(3):673–692. doi: 10.1113/jphysiol.1976.sp011252. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Clay J. R., Shrier A. Analysis of subthreshold pace-maker currents in chick embryonic heart cells. J Physiol. 1981 Mar;312:471–490. doi: 10.1113/jphysiol.1981.sp013639. [DOI] [PMC free article] [PubMed] [Google Scholar]
- DeFelice L. J. Fluctuation analysis in neurobiology. Int Rev Neurobiol. 1977;20:169–208. doi: 10.1016/s0074-7742(08)60653-4. [DOI] [PubMed] [Google Scholar]
- Goldman D. E. POTENTIAL, IMPEDANCE, AND RECTIFICATION IN MEMBRANES. J Gen Physiol. 1943 Sep 20;27(1):37–60. doi: 10.1085/jgp.27.1.37. [DOI] [PMC free article] [PubMed] [Google Scholar]
- HODGKIN A. L., KEYNES R. D. The potassium permeability of a giant nerve fibre. J Physiol. 1955 Apr 28;128(1):61–88. doi: 10.1113/jphysiol.1955.sp005291. [DOI] [PMC free article] [PubMed] [Google Scholar]
- McAllister R. E., Noble D., Tsien R. W. Reconstruction of the electrical activity of cardiac Purkinje fibres. J Physiol. 1975 Sep;251(1):1–59. doi: 10.1113/jphysiol.1975.sp011080. [DOI] [PMC free article] [PubMed] [Google Scholar]
- McDonald T. F., DeHaan R. L. Ion levels and membrane potential in chick heart tissue and cultured cells. J Gen Physiol. 1973 Jan;61(1):89–109. doi: 10.1085/jgp.61.1.89. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Nathan R. D., DeHaan R. L. In vitro differentiation of a fast Na+ conductance in embryonic heart cell aggregates. Proc Natl Acad Sci U S A. 1978 Jun;75(6):2776–2780. doi: 10.1073/pnas.75.6.2776. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Noble D., Tsien R. W. The kinetics and rectifier properties of the slow potassium current in cardiac Purkinje fibres. J Physiol. 1968 Mar;195(1):185–214. doi: 10.1113/jphysiol.1968.sp008454. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Sachs H. G., DeHaan R. L. Embryonic myocardial cell aggregates: volume and pulsation rate. Dev Biol. 1973 Jan;30(1):233–240. doi: 10.1016/0012-1606(73)90064-x. [DOI] [PubMed] [Google Scholar]