On the fixation of catecholamines including adrenaline in tissue sections.

Following intravenous or intraperitoneal injections of 3H-l-dopa radioactivity in adrenal medullary chromaffin cells of the mouse has been followed by autoradiographic and radioisotopic assay methods. For autoradiographic purposes tissues were fixed in either phosphate buffered glutaraldehyde or in 1-5% potassium dichromate in glutaraldehyde pH 7-2. A high initial radioactivity is demonstrated by both autoradiography and radioisotopic assay. During the first hour dopamine is the predominant labelled amine. Between 1 and 4 hours after the injection noradrenaline is in highest concentration and from 1 to 24 hours labelled adrenaline appears and becomes the predominant labelled amine (about 70%) after 24 hours. Autoradiographs of tissues fixed in glutaraldehyde alone confirm that adrenaline is lost from sections by this technique. When 1-5% potassium dichromate is added to glutaraldehyde then adrenline is fixed in A cells and these show only a slightly decreased grain count as compared to NA cells at 5 days; this slight decrease is probably due to more rapid turnover of amines by A cells.