QUANTITATION OF EPINEPHRINE AND NOREPINEPHRINE SECRETION FROM INDIVIDUAL ADRENAL-MEDULLARY CELLS BY MICROCOLUMN HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY

The cellular response of individual adrenal medullary cells to a prolo nged stimulation with carbamylcholine (carbachol) was studied using mi crocolumn high-performance liquid chromatography (MHPLC) with electroc hemical detection. Chromaffin cells will not release all of their cate cholamine stores when continuously exposed to a secretagogue. The proc ess of desensitization prevents the continued release of catecholamine s after a certain percentage of chemical stores have been depleted. Th e percentage of a cell's chemical stores released upon stimulation was determined, and whether there is a difference in release between the cell types was examined. A single cell was exposed to a stimulation so lution for 5.0 min at 25-degrees-C. Approximately 80% of the solution was removed and analyzed on a microcolumn reversed-phase chromatograph y column. A lysing solution was immediately added to the miniaturized vial which still contained the cell, and this solution was also analyz ed chromatographically. The first run was used to determine the amount of catecholamine the cell released upon stimulation. The second run d etermined the amount of catecholamine that remained in the cell. From these values the percentage of catecholamine released was calculated. Twenty-seven individual cells were studied by this method, and 22 coul d be classified as norepinephrine or epinephrine dominant. There was n o statistical difference in the amount of catecholamine the norepineph rine dominant cells released (14 +/- 5%, n = 11) as compared to the ep inephrine dominant cells (12 +/- 4%, n = 11).