In:
American Journal of Physiology-Heart and Circulatory Physiology, American Physiological Society, Vol. 284, No. 4 ( 2003-04-01), p. H1217-H1229
Abstract:
We modeled changes in contractile element kinetics derived from the cyclic relationship between myoplasmic [Ca 2+ ], measured by indo 1 fluorescence, and left ventricular pressure (LVP). We estimated model rate constants of the Ca 2+ affinity for troponin C (TnC) on actin (A) filament (TnCA) and actin and myosin (M) cross-bridge (A · M) cycling in intact guinea pig hearts during baseline 37°C perfusion and evaluated changes at 1) 20 min 17°C pressure, 2) 30-min reperfusion (RP) after 30-min 37°C global ischemia during 37°C RP, and 3) 30-min RP after 240-min 17°C global ischemia during 37°C RP. At 17°C perfusion versus 37°C perfusion, the model predicted: A · M binding was less sensitive; A · M dissociation was slower; Ca 2+ was less likely to bind to TnCA with A · M present; and Ca 2+ and TnCA binding was less sensitive in the absence of A · M. Model results were consistent with a cold-induced fall in heart rate from 260 beats/min (37°C) to 33 beats/min (17°C), increased diastolic LVP, and increased phasic Ca 2+ . On RP after 37°C ischemia vs. 37°C perfusion, the model predicted the following: A · M binding was less sensitive; A · M dissociation was slower; and Ca 2+ was less likely to bind to TnCA in the absence of A · M. Model results were consistent with reduced myofilament responsiveness to [Ca 2+ ] and diastolic contracture on 37°C RP. In contrast, after cold ischemia versus 37°C perfusion, A · M association and dissociation rates, and Ca 2+ and TnCA association rates, returned to preischemic values, whereas the dissociation rate of Ca 2+ from A · M was ninefold faster. This cardiac muscle kinetic model predicted a better-restored relationship between Ca 2+ and cross-bridge function on RP after an eightfold longer period of 17°C than 37°C ischemia.
Type of Medium:
Online Resource
ISSN:
0363-6135
,
1522-1539
DOI:
10.1152/ajpheart.00816.2002
Language:
English
Publisher:
American Physiological Society
Publication Date:
2003
detail.hit.zdb_id:
1477308-9
SSG:
12
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