Direct fluorometric assay of catecholamine secretion from isolated bovine adrenal chromaffin cells

The intrinsic fluorescence of catecholamines can be exploited for a simple and speedy fluorescence assay of secretion from bovine adrenal chromaffin cells. Catecholamines are separated from concomitantly secreted proteins by centrifugation in 0.4 M perchloric acid, and their fluorescence is measured directly in a conventional spectrofluorometer without chemical derivatization. Catecholamine release, assayed by this technique, is virtually identical to data obtained in parallel by the classical trihydroxyindole method. Intrinsic catecholamine fluorescence does not differentiate between epinephrine and norepinephrine. Interferences from small molecular weight compounds not precipitated in perchloric acid are rare, and can be accounted for using appropriate calibration curves.