although guanylylimidodiphosphate , gpp ( nh ) p , had no effect on the affinity or the total number of [ 3h ] prazosin-binding sites in membranes prepared from these cells , the nucleotide decreased the apparent affinity of the agonists ( - ) -epinephrine and ( - ) -norepinephrine in competing for [ 3h ] prazosin-binding sites in both cell types .
C0014563
epinephrine
C0028351
norepinephrine