Effect of cross-bridge kinetics on apparent Ca2+ sensitivity.

Brandt, Philip W.; Cox, Robert N.; Kawai, Masataka; Robinson, Thomas F.

doi:10.1085/jgp.79.6.997

Cited by 148 publications

(57 citation statements)

References 49 publications

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“…1-3). Similar inhibitory effects of Pi have been observed with glycerinated or skinned muscle from pig hearts (Herzig & Riiegg, 1977;Herzig et al 1981) and with skinned rabbit psoas fibres (Brandt et al 1982), though it is not clear whether the Ca2+ and Mg2+ concentrations were kept constant in these earlier studies. More recently there have been preliminary reports of similar effects in skinned fibres from frog (Godt, Fender & Nosek, 1984) and fish (Johnston & Altringham, 1985).…”

Section: Influence Of Pi On the Force-[ca2+] Relationshipsupporting

confidence: 53%

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The effects of inorganic phosphate and creatine phosphate on force production in skinned muscles from rat ventricle.

Kentish¹

1986

The Journal of Physiology

333

186

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SUMMARY1. Thin ventricular trabeculae from rat hearts were skinned with the non-ionic detergent Triton X-100. The isometric force development of these muscles was investigated over a range of Ca2+ concentrations (0-2-200 gM) in the presence of various concentrations of creatine phosphate (CP), creatine and inorganic phosphate (Pi). Creatine (0-30 mM) was without effect on the skinned muscles.5. The inhibitory effects of Pi suggest that a net hydrolysis of CP to Pi and creatine in the myoplasm of intact cardiac cells could reduce force development at a given myoplasmic [Ca2+], especially if the latter was below the level needed to fully activate the myofibrils. This suggestion is discussed in relation to the CP hydrolysis and decrease in force development that are observed in cardiac muscle during hypoxia or ischaemia.

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Section: Influence Of Pi On the Force-[ca2+] Relationshipsupporting

confidence: 53%

“…More recently Brandt, Cox, Kawai & Robinson (1982) reported that, in skinned skeletal fibres, Pi reduced not only the maximum force but also the Ca2+ sensitivity of the myofibrils (i.e. increased the [Ca2+] required for a given degree of myofibrillar activation).…”

Section: Introductionmentioning

confidence: 99%

The effects of inorganic phosphate and creatine phosphate on force production in skinned muscles from rat ventricle.

Kentish¹

1986

The Journal of Physiology

333

186

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“…This will increase the cycling rate of the crossbridges and could result in a rightward shift of the force-[Ca2"] relation. 25 According to the scheme, the combined effect of BDM on both sites will result in the observed experimental effect, an increase in [Ca2+]50% and a reduction in Fmax* In this scheme, we would expect the rate of ATP hydrolysis to be decreased by BDM, which has been shown to be the case in previous reports. '1043…”

Section: Velocity Of Unloaded Shorteningmentioning

confidence: 73%

Contractile deactivation and uncoupling of crossbridges. Effects of 2,3-butanedione monoxime on mammalian myocardium.

Gwathmey¹,

Hajjar²,

Solaro³

1991

Circulation Research

150

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We investigated the effects of 1 and 3 mM 2,3-butanedione monoxime (BDM, diacetyl monoxime) on excitation and contraction of cardiac muscle in several types of preparations at various levels of organization. We selected a concentration of BDM that was not expected to affect sarcolemmal calcium flux and action potential duration in cardiac tissue. Two indicators were used to record intracellular calcium. Aequorin, a bioluminescent calcium indicator, was used in studies with ferret papillary muscle preparations, and fura-2, a fluorescent calcium indicator, was used in studies with guinea pig cardiac myocytes. In both cases, addition of BDM resulted in a reduction of peak intracellular calcium released from the sarcoplasmic reticulum and a reduction of peak twitch force. The duration of the action potential of isolated myocytes was slightly abbreviated in the presence of BDM. In studies on the calcium current in the myocytes, addition of BDM was associated with reduced calcium current at any potential. Peak calcium current was reduced by 7.9±1% in the presence of BDM. In tetanized ferret papillary muscles, BDM reduced maximal calcium-activated force by 30±5% and increased the calcium ion concentration required for half-maximal force by 0.1±0.01 ,uM. The Hill coefficient was reduced from 5.00±0.11 to 3.40+0.20. Maximal shortening velocity of ferret papillary muscles was increased in the presence of BDM from 1.55+±0.24 to 2.04±0.33 mm/sec. Ca2' binding to troponin C in skinned fiber preparations from guinea pig, bovine, and canine hearts was unaffected by addition of up to 10 mM BDM. Our results indicate that BDM affects both calcium availability and responsiveness of the myofilaments to Ca2 . Uncoupling of contractile activation from excitation may also result from altered crossbridge kinetics. (Circulation Research 1991;69:1280-1292 A n agent that apparently uncouples cardiac excitation from contraction,' 2, paradox,3 intracellular calcium mobilization,4 and crossbridge kinetics5-7 and to inhibit contractile function.8 BDM has been shown to affect force-pCa relations in chemically skinned fiber preparations in which the sarcoplasmic reticulum (SR) and sarcolemma have been extracted.9"10 There are conflicting reports as to whether BDM affects slow inward calcium current (Ilc), thereby inducing a negative inotropic effect.10-12 Previous studies have been unable to rule out possible effects of BDM on SR calcium handling.2"10 Because the SR is the predominant intracellular organelle that supplies calcium for activation of force in cardiac muscle, the effect of BDM on this organelle is pivotal in potentially explaining its mechanism of action.Studies using this compound rely on a full understanding of its mechanism of action, yet the mechanism by which BDM produces force inhibition remains unclear. This study was designed to provide greater insight into the mechanisms of contractile deactivation in the presence of BDM. We investi-

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“…Tension was normalized to the maximum tension at pCa 4.66 before plotting. The data were fitted to the Hill equation (eqn (1); Brandt et al 1980Brandt et al , 1982 to determine the cooperativity (n) and the Ca 2+ dissociation constant (K):…”

Section: Pca-tension Measurementsmentioning

confidence: 99%

The Length of Cooperative Units on the Thin Filament in Rabbit Psoas Muscle Fibres

Ding

Fujita

Kawai

2002

Experimental Physiology

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The length of cooperative units along the thin filament of rabbit psoas single muscle fibres was determined by reducing filament length by treatment with the thin filament severing protein, gelsolin, in the presence of Ca2+ and 2,3‐butanedione 2‐monoxime (BDM). The average time for 50% reduction in isometric tension was 6.7 min at 22 °C. The pCa‐tension relationship was measured at 22 °C, pH 7.00 and ionic strength 200 mM, and the data were fitted to the Hill equation to determine the half‐saturation point (K) and the cooperativity (n). Our results demonstrate that the cooperativity does not change much when the remaining isometric tension was in the range 20‐100%. The cooperativity quickly diminished when the remaining tension was reduced to less than 20%. Our results further demonstrate that the change in the pK value was minimal and averaged 0.075 (less Ca2+ sensitive) as the thin filament length was reduced. We infer from the first observation that the thin filament cooperativity extends up to 0.2 μm, which includes the maximum of about four basic cooperative units consisting of seven actin molecules, one tropomyosin dimer and one troponin complex. We infer from the second observation that the Ca2+ sensitivity is slightly reduced by removal of the cooperative interaction between neighbouring cooperative units.

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Effect of cross-bridge kinetics on apparent Ca2+ sensitivity.

Cited by 148 publications

References 49 publications

The effects of inorganic phosphate and creatine phosphate on force production in skinned muscles from rat ventricle.

The effects of inorganic phosphate and creatine phosphate on force production in skinned muscles from rat ventricle.

Contractile deactivation and uncoupling of crossbridges. Effects of 2,3-butanedione monoxime on mammalian myocardium.

The Length of Cooperative Units on the Thin Filament in Rabbit Psoas Muscle Fibres

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