because catecholamines have been reported to stimulate the sodium pump and na+-k+-atpase in skeletal and cardiac muscle , we examined the effects of isoproterenol ( 0.2-1.0 x 10 ( -6 ) m ) and norepinephrine ( 2-4 x 10 ( -7 ) m ) on intracellular sodium activity ( aina ) and twitch tension in dog purkinje strands and ventricular muscles , aina was measured with na+-sensitive microelectrodes .
C0007412
catecholamines
C0028351
norepinephrine