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001-es BibID:	BIBFORM040598
Első szerző:	Ebus, J.
Cím:	Effects of MgATP on ATP utilization and force under normal and simulated ischaemic conditions in rat cardiac trabeculae / J. Ebus, Z. Papp, R. Zaremba, G. J. Stienen
Dátum:	2001
ISSN:	0031-6768
Megjegyzések:	The dependency of ATP utilization and isometric force on [MgATP] was studied in skinned rat trabeculae under normal (pH 7.0) and simulated ischaemic (pH 6.2, 30 mM added Pi) conditions at 20+/-1 degrees C. At saturating [Ca2+], mean (+/-SEM) ATP utilization at 5 mM MgATP (A0) was 0.48+/-0.03 mM/s and force (F0) was 37+/-2 kN/m2. At 10 microM MgATP under normal conditions ATP utilization decreased gradually to 66+/-3% of A0, and force increased to 169+/-7% of F0. Under ischaemic conditions at 10 microM MgATP, ATP utilization decreased from 30+/-5% to 11+/-2% of A0 whereas force increased eightfold from 12+/-4% to 97+/-7% of F0. The [MgATP] at half-maximal ATP utilization (Km) under ischaemic conditions was 21+/-3 microM. At pH 7.0, Km was estimated to be less than 10 microM. These results show that tension cost decreases markedly with decreasing MgATP. Under ischaemic conditions parallel changes in Ca2+ sensitivity of force and ATP utilization were observed, corresponding to 1.3 pCa units. Reducing [MgATP] from 0.5 to 0.05 mM caused a modest reversal of this change in Ca2+ sensitivity. These changes in Ca2+ sensitivity are consistent with a marked reduction in active force and force-related ATP utilization during ischaemia but are insufficient to explain the ischaemic contracture on the basis of active force development.
Tárgyszavak:	Orvostudományok Klinikai orvostudományok idegen nyelvű folyóiratközlemény külföldi lapban
Megjelenés:	Pflugers Archiv-European Journal Of Physiology. - 443 : 1 (2001), p. 102-111. -
További szerzők:	Papp Zoltán (1965-) (kardiológus, élettanász) Zaremba, Ruud Stienen, Ger J. M.
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001-es BibID:	BIBFORM040570
Első szerző:	Stienen, Ger J. M.
Cím:	Calcium modulates the influence of length changes on the myofibrillar adenosine triphosphatase activity in rat skinned cardiac trabeculae / G. J. M. Stienen, Z. Papp, G. Elzinga
Dátum:	1993
ISSN:	0031-6768
Megjegyzések:	The relationship between adenosine triphosphate (ATP) turnover and muscle performance was investigated in skinned cardiac trabeculae of the rat at different [Ca2+] and two different sarcomere lengths (1.8 microns and 2.2 microns) at 20 degrees C. ATP turnover was measured photometrically by enzymatic coupling of the regeneration of ATP to the oxidation of reduced nicotinamide adenine dinucleotide. The trabeculae were studied under isometric conditions and when the length was altered repetitively at a frequency of 23 Hz, with a square wave, by 5% of the initial length. The isometric ATPase activity amounted to 0.48 mM/s. Isometric ATP turnover and force were proportional at different [Ca2+]. During length changes at maximal activation (pCa 4.27) and 2.2 microns sarcomere length, ATPase activity increased to up to 162% whereas at low [Ca2+], ATPase activity decreased with respect to the isometric value at that pCa. At pCa 5.5, ATPase activity was reduced to 33%. These results indicate that during the length changes the apparent cross-bridge detachment rate is increased and the apparent attachment rate is decreased. The findings suggest that the Fenn effect, i.e. the increase in energy turnover above the isometric value during shortening, is present in cardiac trabeculae at high levels of activation, but is absent or reversed at lower levels of activity.
Tárgyszavak:	Orvostudományok Klinikai orvostudományok idegen nyelvű folyóiratközlemény külföldi lapban
Megjelenés:	Pflügers Archiv. - 425 : 3-4 (1993), p. 199-207. -
További szerzők:	Papp Zoltán (1965-) (kardiológus, élettanász) Elzinga, G.
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