Sensitivity to adrenocorticotropic hormone during adaptation to increased muscle activity.

Systematical muscle exercises increased sensitivity of adrenals to ACTH in adult albino rats, while fatigue decreased it. The sensitivity of adenylatecyclase of fat cells to ACTH does not change during the adaptation of organism to increased muscular activity. Activation of adenylate cyclase of fat cells with epinephrine is abolished by sympatholytin which, however, has no effect on the ACTH activation. These findings confirm that the adenylate cyclase receptors for epinephrine and for ACTH are different.