Role of calcium in the phenylephrine-induced activation of phosphorylase "A" in isolated liver cells.
The ability of phenylephrine to activate phosphorylase in liver cells with variable degrees of Ca2+ loading was studied. Phenylephrine has been found to be capable of stimulating phosphorylase at saturating Ca2+ concentrations that precluded any further action of this ion. Furthermore the degree of activation was proportional to the cellular calcium content. These results allow to conclude that alpha-adrenergic agonists activate phosphorylase by a mechanism apparently unrelated to their ability to mobilize and subsequently increase the cytosolic concentration of free Ca2+.
Saz
J M
JM
Endocrine Physiology Unit, Centro de Investigaciones Biológicas, Madrid, Spain.
Gonzalez-Manchon
C
C
Ayuso
M S
MS
Parrilla
R
R
D000818:Animals; D002118:Calcium / Q000502:physiology*; D003600:Cytosol / Q000201:enzymology / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D008099:Liver / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism; D008297:Male; D010656:Phenylephrine / Q000494:pharmacology*; D010762:Phosphorylase a / Q000378:metabolism*; D006005:Phosphorylases / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains
D010656:Phenylephrine; D010762:Phosphorylase a; D006005:Phosphorylases; D002118:Calcium