IMMUNOHISTOCHEMICAL AND ULTRASTRUCTURAL EVIDENCE OF ADRENAL CHROMAFFIN CELL SUBTYPES IN SEA BASS DICENTRARCHUS-LABRAX (L)

Histology demonstrated chromaffin cells in the head kidney and opistho nephros of the sea bass. Immunohistochemistry showed the catecholamine -synthesizing enzymes tyrosine hydroxylase and dopamine beta-hydroxyla se in these cells. Phenylethanolamine N-methyltransferase was detected in a fraction of the chromaffin cells in the head kidney (59%) and in the opisthonephros (54%). Distinct noradrenaline- and adrenaline-synt hesizing cells are therefore suggested. Ultrastructural analysis confi rmed the existence of two main chromaffin cell types, distinguished by different types of the secretory granules. Cells that contain vesicle s with a round, electron-dense core were interpreted as noradrenaline cells, while cells with electron-lucent vesicles were identified as ad renaline cells. The ultrastructure of these chromaffin cell subtypes d oes not differ in the head kidney and opisthonephros. A minor populati on of chromaffin cells was identified, which typically show smaller ve sicles with an electron-dense core. This population may account for a limited number of not fully differentiated chromaffin cells. (C) 1996 Academic Press, Inc.