Adrenergic receptors are a fallible index of adrenergic denervation hypersensitivity

Abstract

In view of evidence that neither interindividual nor induced intra-individual variations of adrenergic receptor status are related to metabolic or haemodyna-mic sensitivity to adrenaline in vivo, we took an alternative approach to assessment of the relevance of adrenergic receptor measurement by measuring these in a group of subjects with well-documented adrenergic denervation hypersensitivity, patients with diabetic autonomic neuropathy. Mononuclear leukocyte β₂-adrenergic receptor densities (and binding affinities), measured with ¹²⁵I-labelled pinodolol, and isoproterenol-stimulated cyclic AMP accumulation, in samples from patients with insulin-dependent diabetes mellitus (IDDM) with diabetic autonomic neuropathy (n=8), were no different from those in samples from patients with IDDM without neuropathy (n=8), or from non-diabetic subjects (n=8). In addition, platelet α₂-adrenergic receptor densities (and binding affinities), measured with ³H-labelled yohimbine, and adrenaline-induced suppression of cyclic AMP contents did not differ among the three groups. Thus, in contrast to idiopathic autonomic failure, there is no generalized increase in adrenergic receptors in autonomic failure due to diabetic autonomic neuropathy. Regardless of the mechanism of adrenergic denervation hypersensitivity in such patients, these data provide further evidence that measurements of cellular adrenergic receptors (and adenylate cyclase) in vitro are a fallible index of sensitivity to catecholamines in vivo.

Key Words:

• catecholamines
• diabetic autonomic neuropathy