Reduced L-type calcium current in the embryonic chick heart with persistent truncus arteriosus.
Calcium currents were examined in an experimental model in the embryonic chick heart with a congenital malformation known as persistent truncus arteriosus. This is a severe defect characterized by failure of conotruncal and aorticopulmonary septation of the embryonic heart tube. As a result, no separation into the aortic and pulmonary arteries occurs, and there is a common outflow tract. The hearts with persistent truncus arteriosus had a 26% greater ventricular to whole embryo weight, which indicated that the ventricles were enlarged. Both the low-threshold T-type (ICa.T) and the 1,4-dihydropyridine-sensitive L-type (ICa.L) Ca2+ currents were present in the ventricular myocytes from hearts at day 11 of incubation. However, day 11 hearts with persistent truncus arteriosus showed a twofold reduction in the peak magnitude of ICa.L at a test potential of + 10 mV without a concomitant reduction in the number of L channels detected by 1,4-dihydropyridine antagonist [(+)[3H]PN200-110] and agonist (Bay K 8644) receptor binding. The results indicated that an L channel regulatory mechanism other than protein synthesis was affected. These changes are consistent with responses to conditions of excessive hemodynamic burden that have been characterized in adult hearts.
Department of Anatomy, Medical College of Georgia, Augusta 30912-2000.
T L
TL
Creazzo
D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D000818:Animals; D002118:Calcium / Q000502:physiology*; D002121:Calcium Channel Blockers / Q000378:metabolism; D015220:Calcium Channels; D002642:Chick Embryo; D004594:Electrophysiology; D006321:Heart / Q000503:physiopathology*; D017275:Isradipine; D009206:Myocardium / Q000378:metabolism; D010069:Oxadiazoles; D011978:Receptors, Nicotinic / Q000378:metabolism; D014339:Truncus Arteriosus, Persistent / Q000196:embryology / Q000503:physiopathology*
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D010069:Oxadiazoles; D011978:Receptors, Nicotinic; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D002118:Calcium; D017275:Isradipine