α-Adrenergic receptors modulate β-receptor affinity in rat kidney membranes

Abstract

Adrenergic receptors were first classified into two classes—α and β—on the basis of the relative pharmacological potencies of agonist compounds¹, and this classification has been supported by subsequent studies. In some tissues, such as the heart and liver^2,3, they exert similar physiological responses, and in other tissues, such as the uterus and vasculature, they have opposing roles^4,5. The occurrence of both classes of receptor in the same tissue leads to the problem of what determines whether the overall response observed is α-type or β-type, as adrenaline and noradrenaline bind to both receptor classes. Furthermore, direct binding studies have demonstrated that the two receptor classes are distinct and separate entities⁶. We show here that stimulation of α-receptors in renal membranes causes a specific decrease in the affinity of the agonist compound isoprenaline for β-receptors in the same membranes. This demonstrates that interactions occur between renal α- and β-adrenergic receptors. Such interactions may modulate the response of the kidney to sympathetic stimulation.