DECREASED CARDIAC β-ADRENOCEPTORS IN HYPERTENSIVE RATS

1. β-Adrenoceptors have been investigated in cardiac and renal cell membranes from hypertensive and normal rats. 2. The ¹²⁵I-labelled β-adrenoceptor antagonist l-(4-iodophenoxy)-3-isopropyl-aminopropan-2-ol was used to measure directly the number and affinity of receptors. 3. Cardiac membranes from hypertensive rats had a lower concentration of β-adrenoceptors than membranes from control normotensive animals, but the affinities of the receptors remained unchanged. Receptor concentration decreased by half and was similar in each of the three models of experimental hypertension investigated. 4. In contrast, kidney membranes from hypertensive animals had the same β-adrenoceptor concentration and affinity as membranes from normotensive rats. 5. The decrease in cardiac β-adrenoceptor concentration may reflect an increase in cardiac sympathetic drive in these experimental hypertensive models.