Length-dependent activation by Ba2+ and Sr2+ of skinned cardiac and skeletal muscle of the rabbit.
Am J Physiol
; 260(3 Pt 1): C609-17, 1991 Mar.
Article
en En
| MEDLINE
| ID: mdl-2003582
ABSTRACT
Over a wide range of sarcomere lengths, force activation by Ca2+, Ba2+, and Sr2+ was studied in papillary muscle and in fast skeletal fibers of the gracilis muscle of the rabbit, both skinned by means of freeze drying. The length-tension relations of Ba2+ activation differ significantly from those of Sr2+ and Ca2+ activation with respect to both the value and the position of the maximum. At (almost) full activation, force induced in gracilis muscle by Ba2+ was 50% of the developed force induced by Ca2+. The position of the Sr2+ sensitivity curve for papillary muscle preparations is independent of sarcomere length, in contrast to the position of the Ca2+ sensitivity curves. The binding of Sr2+ to the papillary preparation proves to be very stable as observed from the long-lasting relaxation after activation. Immersion of the papillary preparation in the relaxation fluid after activation with Ba2+ results in a tension transient a rise in tension followed by a decrease was observed. The maximal value of the tension transient was up to twice the steady tension, dependent on Ba2+ concentration. The steady-state tension was approximately 50% of the Ca2(+)-induced tension. Ba2+ sensitivity curves are not sigmoidal but show a maximum. Above [Ba2+] greater than 10(-5) to 10(-4) M (dependent on sarcomere length) tension decreased. These observations suggest that two counteracting processes govern Ba2+ contraction in papillary muscle preparations, namely activation and inhibition.
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Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Músculos Papilares
/
Estroncio
/
Bario
/
Contracción Muscular
/
Músculos
Límite:
Animals
Idioma:
En
Revista:
Am J Physiol
Año:
1991
Tipo del documento:
Article
País de afiliación:
Países Bajos