The effect of lanthanum on the mechanical function of the isolated perfused rat heart at different extracellular calcium concentrations.
The effects of 50 microM lanthanum (La3+) on the contractile force, rate and coronary flow of rat hearts perfused with solutions containing 2.5, 5, 7.5 mM calcium (Ca2+) have been investigated. La3+ produced a rapid and marked decrease in contractile force within 1-3 min ("early La(3+)-effect"). The inhibition of contractility by La3+ was reduced progressively when the Ca2+ ion concentration in the perfusion fluid was raised from 2.5 to 7.5 mM. However, after 10-80 min of La3+ perfusion the contractile force was increased significantly ("late La(3+)-effect"). Elevation of Ca2+ during exposure to La3+ increased its effect. During the late La(3+)-effect, a marked decrease in heart rate and a significant increase in time to reach peak tension, time for half relaxation and twitch duration was observed. High concentrations of perfusate Ca2+ decreased the chronotropic response to La3+, in contrast, elevated Ca2+ potentiated La(3+)-induced increase in time to reach peak tension, time for half relaxation and twitch duration. La3+ produced a significant decrease in coronary flow. High Ca2+ augmented the decrease coronary flow. The findings indicate that La3+ may produce marked effects on myocardial function. High extracellular Ca2+ reduces the La(3+)-induced initial decrease in force of contraction, but potentiates the late increase in contractile force by La3+. Elevated external Ca2+ also increases the effects of La3+ on twitch parameters, heart rate and coronary flow.
Kaygisiz
Z
Z
Department of Physiology, Cardiology Faculty of Medicine, University of Anadolu, Eskisehir, Turkey.
Akin
M Z
MZ
Basaran
A
A
Günes
H V
HV
Timuralp
B
B
D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D003326:Coronary Circulation / Q000187:drug effects; D004594:Electrophysiology; D005260:Female; D006321:Heart / Q000502:physiology*; D006339:Heart Rate / Q000187:drug effects*; D006439:Hemodynamics / Q000187:drug effects*; D007811:Lanthanum / Q000494:pharmacology*; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects; D010477:Perfusion; D051381:Rats; D011919:Rats, Inbred Strains
D007811:Lanthanum; D002118:Calcium