Dual trophic effects of the alpha 1-adrenergic receptor in cultured neonatal XXXX heart muscle cells.

@entity8580 @entity1184 @entity1283 @entity1425 @entity35 @entity1063
The molecular signals regulating @entity1283 are unknown. We used a new model system to study this problem. Muscle cells from the neonatal @entity35 ventricle were cultured in serum-free medium. Control cells did not change in size over time and did not show spontaneous contractile activity. Incubation with @entity1063 or @entity1425 had two major trophic effects that developed over 1-2 days. The first was stimulation of muscle cell @entity1184 or increase in size. The second was induction of spontaneous contractile activity. The @entity1184 response was mediated through an alpha 1-adrenoceptor. The beating response required both alpha 1- and beta 1-adrenergic receptor stimulation. Alpha 1 stimulation alone produced enlarged cells that did not beat. Alpha 1 plus beta 1 stimulation induced contractile activity even when protein synthesis and @entity1184 were inhibited. Thus, the two alpha 1 responses could be dissociated, providing evidence for two independently-regulated cellular pathways for the dual alpha 1 trophic effects. One pathway leads to @entity1184 . The other, which requires concomitant beta 1 stimulation, controls the development of beating. Preliminary work raises the possibility that different products of @entity8580 phospholipid hydrolysis might initiate the two alpha 1 trophic pathways. Other preliminary work suggests that the growth pathway is associated with the expression of specific genes and might reflect an action of the alpha 1-adrenoceptor on the cell nucleus. These studies define previously unsuspected trophic roles for the alpha 1-adrenergic receptor.
