Reversible norepinephrine binding to rabbit myometrium: relationship to sites of known biological significance

Catecholamines bind specifically to several cell types and subcellular fractions. This binding is not consistent with binding to the adrenergic receptor. Catecholamines would be expected to bind to sites other than the adrenergic receptor (uptake 1, uptake 2, nerve vesicles, catecholamine-O-methyl transferase and serum albumin). We characterized the binding of 3H-norepinephrine to microsomes prepared from rabbit myometrium. In the presence of antioxidant binding was reversible and 3H-norepinephrine could be recovered bound to microsomes or free in incubation media. The binding was not characteristic of binding to any one known biological site. It may represent binding to a mixture of these sites or may be fortuitous binding to sites of unknown biological significance.