Renal beta-adrenoceptors in thyroxine-treated rats.

The number of beta-adrenoceptors was measured in cardiac and renal cortex membranes from controls and thyroxine-treated rats. Two methods of membrane preparation (sucrose- and KCl-extraction) were compared. KCl-extraction yielded a higher number of beta-adrenoceptors, accompanied by increased activity of the plasma membrane enzyme marker 5'-nucleotidase. Thyroxine increased the number of beta-adrenoceptors in both cardiac and renal cortex membranes prepared with both methods. These results suggest that: i) Enrichment of the membrane fraction may explain the higher number of beta-adrenoceptors found with KCl, ii) Thyroid hormone plays a role in the regulation of beta-adrenoceptors in the renal cortex.