Adrenocorticotropin binding sites in rat cardiac tissue

Using the ACTH analog [125I-Tyr23,Phe2,Nle4] ACTH(1-24), the existence of specific binding sites for ACTH in atrial membrane preparations was demonstrated. The dissociation constants (Kd), determined by Scatchard analysis were not significantly different for membrane preparations of adrenal gland or atrial tissue (being 6.40 x 10(-12)M and 8.86 x 10(-12)M respectively). No binding was observed to membrane preparations from kidney or lung. While the binding of the ACTH(1-24) analog to atrial membranes was inhibited by ACTH(1-24), it was not affected by norepinephrine or epinephrine. It was proposed that the ACTH(1-24) analog may bind to sites located on the adrenergic nerve endings associated with the cardiac tissue, and that such binding would interfere with the neuronal reuptake of the catecholamines.