[Use of tonic contracture of strips of frog myocardium to study sodium-calcium exchange in the sarcolemma of myocardiocytes].
The mechanism of tonic component of the frog myocardium potassium contraction was studied. The degree of contraction depended on the potassium, sodium and calcium ions concentrations in extracellular medium. The tonic component of hyperpotassium contraction, as well as the additional contractions due to hyposodium and hypercalcium medium in the tonic component phase seems to stem from activation of sodium--calcium exchange. The latter through the sarcolemma of the heart cells was 3Na: 1Ca. The effect of some mono- and bivalent cations on sodium-calcium exchange in respect ot their inhibiting activity was as follows: Cd+2 greater than Sr+2 greater than Ba+2 greater than Mn+2 much greater than Mg+2 greater than Li+ greater than Cs+.
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002463:Cell Membrane Permeability; D066298:In Vitro Techniques; D008564:Membrane Potentials; D009200:Myocardial Contraction; D009206:Myocardium / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism; D011896:Rana temporaria; D012508:Sarcolemma / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism*
D012964:Sodium; D011188:Potassium; D002118:Calcium
Ispol'zovanie tonicheskoĭ kontraktury polosok miokarda liagushki dlia izucheniia natriĭ-kal'tsievogo obmena v sarkolemme kardiomiotsitov.