Perturbations of the trans-sarcolemmal and sarcoplasmic @entity141 transport contribute to the abnormal myocardial activity provoked by @entity519 and reoxygenation. Whether @entity141 pools of the extracellular compartment and sarcoplasmic reticulum (SR) are involved to the same extent in the @entity409 of the anoxic-reoxygenated immature heart has not been investigated. Spontaneously contracting hearts isolated from 4-day-old @entity1573 embryos were submitted to repeated @entity519 (1 min) followed by reoxygenation (5 min). Heart rate, atrioventricular propagation velocity, ventricular shortening, velocities of contraction and relaxation, and incidence of @entity943 were studied, recorded continuously. Addition of @entity1855 (10 nM), which blocks selectively sarcolemmal L-type @entity141 channels, was expected to protect against excessive entry of extracellular @entity141 , whereas addition of @entity8452 (10 nM), which opens the SR @entity141 release channel, was expected to increase cytosolic @entity141 concentration. @entity1855 (a) had no dromotropic effect by contrast to adult heart, (b) attenuated ventricular contracture induced by repeated @entity519 , (c) shortened cardioplegia induced by reoxygenation, and (d) had remarkable antiarrhythmic properties during reoxygenation specially. On the other hand, @entity8452 potentiated markedly @entity943 both during @entity519 and at reoxygenation. Thus despite its immaturity, the SR seems to be functional early in the developing @entity1573 heart and involved in the reversible @entity409 induced by @entity519 -reoxygenation. Moreover, @entity141 entry through L-type channels appears to worsen @entity943 especially during reoxygenation. These findings show that the @entity141 -handling systems involved in irregular activity in immature heart, such as the embryonic @entity1573 heart, may differ from those in the adult.

Effects of XXXX and @entity8452 on activity of the embryonic @entity1573 heart during @entity519 and reoxygenation.

@entity1855 :: ('MESH:D014700', 'Chemical') :: ['verapamil', 'Verapamil'] @entity8452 :: ('MESH:D012433', 'Chemical') :: ['ryanodine'] @entity409 :: ('MESH:D008107', 'Disease') :: ['dysfunction'] @entity1573 :: ('9031', 'Species') :: ['chick'] @entity519 :: ('MESH:D000860', 'Disease') :: ['anoxia'] @entity141 :: ('CHEBI:29108', 'Chemical') :: ['Ca2+'] @entity943 :: ('MESH:D001145', 'Disease') :: ['arrhythmias']
@entity1855 :: (MESH:D014700,Chemical) :: ['verapamil']
