The effect of aging on extra-adrenal catecholamine storing cells of the rat.

Cell number and catecholamine histofluorescence were determined in three extra-adrenal chromaffin tissues: the abdominal paraganglia, the carotid body and SIF (small intensely fluorescent)-cells, of male Fischer-344 rats at different ages. Catecholamines were demonstrated using the formaldehyde-induced fluorescence method. The number of paraganglia cells in the retroperitoneal area increased 13.6 fold between 3 and 33 months of age, and the volume of abdominal paraganglia approached 65% of the volume of one adrenal medulla. The emission color of some paraganglia cells shifted from greenish-yellow to yellowish-brown with aging, but differences were not observed in cell number of fluorophore color in the carotid body, a chemoreceptor type of paraganglion. The number of SIF cells (an intraganglionic variant of extra-adrenal chromaffin tissue) in the hypogastric ganglion increased significantly between 3 and 33 months. The pronounced increase of the volume of the paraganglia in aged rats may contribute to elevated concentrations of circulating catecholamines in these animals.