1 resultado para Ca2 Transient
em Memorial University Research Repository
Resumo:
The Atlantic cod, Gadus morhua, differs from many teleosts in that its heart does not respond to adrenergic stimulation, and is more capable of maintaining function during acute temperature changes. To examine if differences in intracellular calcium mobilization are associated with these atypical responses, confocal microscopy was used to study the calcium handling of cardiac cells from Atlantic cod vs. steelhead trout at their acclimation temperature (10C), or subjected to acute temperature changes (to 4 and 16C), while being stimulated across a range of frequencies (10 110 min). In addition, cells were tested with and without tonic (10 nM) levels of adrenaline at 10C, and pharmacological blockers were used to study the relative contributions of the L-type Ca channel, sarcoplasmic reticulum and Na+/Ca exchanger to the Ca transient. Consistent with previous in vitro and in situ studies, there were few significant effects of adrenaline on the Ca transient of cod cardiomyocytes, yet adrenaline had significant positive inotropic effects on trout cardiomyocytes. At 10C, peak Ca (F/F) only differed between the two species at low stimulation frequencies (10, 30 min-1), with trout F/F 25-35% higher. In contrast, the time to peak Ca and the time to half relaxation were both shorter (by 10 35% across frequencies) in cod. Acute temperature changes caused a shift in the Ca - frequency relationship in both species, with F/F values higher for trout at low frequencies (< 70 min) at 4C, whereas this parameter was greater at all frequencies except 10 min in cod at 16C. Unfortunately, these experiments did not highlight clear species differences in the relative contributions of the L-type Ca channels, sarcoplasmic reticulum and Na+/Ca exchange to the Ca transient.
