STUDIES OF CHEMICAL NATURE OF ALPHA-ADRENERGIC RECEPTOR .4. LABELING STUDIES ON NERVE-FREE RABBIT AORTIC STRIPS

Since epinephrine protects uptake sites in sympathetic nerve terminals in addition to α-adrenergic receptors from combination with 14C-Dibenamine hydrochloride a procedure was developed for denervation of rabbit aorta. With epinephrine as protecting agent in these nerve-free rabbit aortic strips the significant increment in radioactivity associated with unprotected strips as compared to protected strips was confined to the lipid-free residue. This observation provided further evidence that the α-adrenergic receptor is not lipid in nature. In intact aortic strips phentolamine (1 × 10-5) conferred complete protection against blockade by 14C-Dibenamine hydrochloride (3 × 10-6) and a significant difference was found in the radioactivity of unprotected and protected strips. Although phentolamine (1 × 10-5) conferred 100 per cent protection against blockade by 14C-Dibenamine hydrochloride (3 × 10-6) in nerve-free rabbit aortic strips no significant difference was detected in the radioactivity of unprotected and protected strips. © 1969.