Influence of thyroid state on the specific binding of noradrenaline to a cardiac particulate fraction and on catecholamine-sensitive cardiac adenylate cyclase activity.

Specific binding of [3H] noradrenaline, possibly to beta-adrenoreceptors, and adrenaline-sensitive adenylate cyclase activity were measured in particulate preparations from the myocardium of hypothyroid, euthyroid, and hyperthyroid rats. Noradrenaline affinity to the binding sites was decreased and the dose-response curve for the stimulation of adenylate cyclase activity by adrenaline was shifted to the right in hypothyroidism. The opposite changes (an increase in noradrenaline affinity and a shift in the adrenaline-adenylate cyclase dose-response curve to the left) were associated with the hyperthyroid state. These findings correlate well with the result of numerous studies according to which thyroid hormone increases and thyroid hormone deprivation decreases the sensitivity of the myocardium to cardiac sympathetic stimulation and circulating catecholamines.