in the presence of gtp , concentrations of catecholamines required to enhance cyclase activity 15 % of the maximum obtainable with isoproterenol ( ec15 ) were 2.0 x 10 ( -7 ) m and 5.5 x 10 ( -8 ) m for trimetoquinol and isoproterenol , respectively .
C0007412
catecholamines
C0022245
isoproterenol