Cow ventricular muscle
- 22 Downloads
The effect of [K]0 on the current-voltage relationship is described. In the negative potential range the curves cross over as [K]0 is increased. At positive potentials the curves re-cross so that in low [K]0 there is more outward current than in high [K]0
Chord conductance has been calculated from the current-voltage relationship and this is taken as a measure ofgK. It is shown thatgK is a function of both the potassium driving force (EM−EK) and [K]0.
Current-voltage relationships obtained by the voltage clamp technique have been compared to net current-voltage relationships obtained by phase plane analysis of the action potential. [K]0 is shown to have similar effects on both.
The effect of [K]0 at positive potentials suggests that delayed outward current during large depolarizing voltage clamp steps is due to an activation of a time-dependent outward current and not to potassium accumulation. An analysis of current tails also suggests the presence of a time-dependent outward current.
In contrast delayed outward current changes during small depolarizing voltage clamp steps are probably due to potassium accumulation.
Evidence is presented which indicates that inward current tails following depolarizing voltage clamp steps are due to potassium accumulation.
Key wordsHeart Extracellular potassium concentration Current-voltage relationship Action potential Time-dependent outward current
Unable to display preview. Download preview PDF.
- Bassingthwaighte JB, Fry CH, McGuigan JAS (1976) Relationship between internal calcium and outward current in mammalian ventricular muscle: a mechanism for the control of action potential duration? J Physiol (Lond) 262:15–37Google Scholar
- Baumgarten CM, Isenberg G (1977) Depletion and accumulation of potassium in the extracellular clefts of cardiac Purkinje fibres during voltage clamp hyperpolarization and depolarization. Pflügers Arch 368:19–31Google Scholar
- Beeler GW, Reuter H (1970) Voltage clamp experiments on ventricular myocardial fibres. J Physiol (Lond) 207:165–190Google Scholar
- Cleemann L, Morad M (1979a) Extracellular potassium accumulation in voltage-clamped frog ventricular muscle. J Physiol (Lond) 286:83–111Google Scholar
- Cleemann L, Morad M (1979b) Potassium currents in frog ventricular muscle: evidence from voltage clamp currents and extracellular K accumulation. J Physiol (Lond) 286:113–143Google Scholar
- Colatsky TJ (1977) The effects of rate and calcium on repolarization in dog Purkinje fibers. Thesis. University of New York at BuffaloGoogle Scholar
- Déléze J (1959) Perfusion of a strip of mammalian ventricle. Effects of K-rich and Na-deficient solutions on transmembrane potentials. Circ Res 7:461–465Google Scholar
- Hagiwara S, Yoshii M (1979) Effects of internal potassium and sodium on the anomalous rectification of the starfish egg as examined by internal perfusion. J Physiol (Lond) 292:251–265Google Scholar
- Hall AE, Hutter OF, Noble D (1963) Current-voltage relations of Purkinje fibres in sodium-deficient solutions. J Physiol (Lond) 166:225–240Google Scholar
- Hille B, Schwarz W (1978) Potassium channels as multi-ion single file pores. J Gen Physiol 72:409–442Google Scholar
- Lee COK, Fozzard HA (1975) Activities of potassium and sodium ions in rabbit heart muscle. J Gen Physiol 65:695–708Google Scholar
- Maughan DW (1976) Potassium movement during hyperpolarization of cardiac muscle. J Memb Biol 28:241–262Google Scholar
- McAllister RE, Noble D (1966) The time and voltage dependence of the slow outward current in cardiac Purkinje fibres. J Physiol (Lond) 186:632–662Google Scholar
- McDonald TF, Trautwein W (1978) The potassium current underlying delayed rectification in cat ventricular muscle. J Physiol (Lond) 274:217–246Google Scholar
- McGuigan JAS (1974) Some limitations of the double sucrose gap, and its use in a study of the slow outward current in mammalian ventricular muscle. J Physiol (Lond) 240:775–806Google Scholar
- Noble D (1965) Electrical properties of cardiac muscle attributable to inward going (anomalous) rectification. J Cell Comp Physiol 66:127–136Google Scholar
- Noble D (1975) The initiation of the heart beat. Clarendon Press OxfordGoogle Scholar
- Noble SJ (1976) Potassium accumulation and depletion in frog atrial muscle. J Physiol (Lond) 258:579–613Google Scholar
- Paes de Carvalho A, Hoffman BF, de Paula Carvalho M (1969) Two components of the cardiac action potential. I. Voltage-time course and the effect of acetylcholine on atrial and nodal cells of the rabbit heart. J Gen Physiol 54:607–635Google Scholar
- Reuter H, Scholz H (1977) A study of the ion selectivity and the kinetic properties of the calcium-dependent slow inward current in mammalian cardiac muscle. J Physiol (Lond) 264:17–47Google Scholar
- Sperelakis N, Shumaker HK (1968) Phase-plane analysis of cardiac action potetials. J Electrocardiol 1:31–42Google Scholar
- Surawicz B, Gettes LS (1963) Two mechanisms of cardiac arrest produced by potassium. Circ Res 12:415–421Google Scholar
- Trautwein W, McDonald TF, Tripathi O (1975) Calcium conductance and tension in mammalian ventricular muscle. Pflügers Arch 354:55–74Google Scholar
- Trautwein W, McDonald TF (1978) Current-voltage relationships in ventricular muscle preparations from different species. Pflügers Arch 374:79–89Google Scholar