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Titolo:
HIGH IONIC-STRENGTH AND LOW PH DETAIN ACTIVATED SKINNED RABBIT SKELETAL-MUSCLE CROSSBRIDGES IN A LOW FORCE STATE
Autore:
SEOW CY; FORD LE;
Indirizzi:
UNIV CHICAGO HOSP & CLIN,CARDIOL SECT,5841 S MARYLAND AVE CHICAGO IL 60637 UNIV CHICAGO,DEPT MED,CARDIOL SECT CHICAGO IL 60637
Titolo Testata:
The Journal of general physiology
fascicolo: 4, volume: 101, anno: 1993,
pagine: 487 - 511
SICI:
0022-1295(1993)101:4<487:HIALPD>2.0.ZU;2-X
Fonte:
ISI
Lingua:
ENG
Soggetto:
X-RAY-DIFFRACTION; FROG-MUSCLE; SHORTENING VELOCITY; MYOSIN SUBFRAGMENT-1; SINGLE FIBERS; PSOAS FIBERS; CONTRACTION; CALCIUM; ACTIN; ASSOCIATION;
Tipo documento:
Article
Natura:
Periodico
Citazioni:
46
Recensione:
Indirizzi per estratti:
Citazione:
C.Y. Seow e L.E. Ford, "HIGH IONIC-STRENGTH AND LOW PH DETAIN ACTIVATED SKINNED RABBIT SKELETAL-MUSCLE CROSSBRIDGES IN A LOW FORCE STATE", The Journal of general physiology, 101(4), 1993, pp. 487-511

Abstract

The effects of varying pH and ionic strength on the force-velocity relations and tension transients of skinned rabbit skeletal muscle were studied at 1-2-degrees-C. Both decreasing pH from 7.35 to 6.35 and raising ionic strength from 125 to 360 mM reduced isometric force by about half and decreased sarcomere stiffness by about one-fourth, so that the stiffness/force ratio was increased by half. Lowering pH also decreased maximum shortening velocity by approximately 29%, while increasing ionic strength had little effect on velocity. These effects on velocity were correlated with asymmetrical effects on stiffness. The increase in the stiffness/force ratio with both interventions was manifest as a greater relative force change associated with a sarcomere length step. This force difference persisted for a variable time after the step. At the high ionic strength the force difference was long-lasting after stretches but relaxed quickly after releases, suggesting that thestructures responsible would not impose much resistance to steady-state shortening. The opposite was found in the low pH experiments. The force difference relaxed quickly after stretches but persisted for a long time after releases. Furthermore, this force difference reached a constant value of approximately 8% of isometric force with intermediatesizes of release, and was not increased with larger releases. This value was almost identical to the value of an internal load that would be sufficient to account for the reduction in maximum velocity seen at the low pH. The results are interpreted as showing that both low pH and high ionic strength inhibit the movement of crossbridges into the force-generating parts of their cycle after they have attached to the actin filaments, with very few other effects on the cycle. The two interventions are different, however, in that detained bridges can be detached readily by shortening when the detention is caused by high ionic strength but not when it is caused by low pH.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 05/12/20 alle ore 01:29:36