in the presence of 10-5 m gtp , histamine produced a maximal stimulation of 1.54 +/- 0.06 times basal activity in left ventricle ( 39 % of the isoproterenol maximum ) , which rose to 1.75 +/- 0.14 times basal activity ( 68 % of the isoproterenol maximum ) in the presence of a 10-5m concentration of the synthetic guanyl nucleotide 5'-guanylyl imidodiphosphate .
C0018353
gtp
C0018366
guanyl