Relationship between maximum chronotropic response to isoproterenol in man and generation of cyclic adenosine monophosphate by lymphocytes.

The maximum change in heart period caused by bolus doses of isoproterenol was measured in 10 normal subjects. This was linearly related to the amount of cyclic adenosine monophosphate generated from lymphocytes in the same subjects in vitro after incubation with isoproterenol. This high correlation between cardiac and lymphocyte beta-adrenoceptor stimulation suggests that maximum response does not depend on innervation. Other factors, such as cell membrane properties or levels of circulating catecholamines, may be of greater importance.