Abstract
This work presents the distribution, histology and ultrastructure of chromaffin cells (CCs) and interrenal tissue (It) in the head kidney of Epinephilus tuvina.
Chromaffin cells are endocrine cells, found in small groups under the endothelium of the posterior cardinal vein (PCV) and its branches which involved the head kidney, and mostly closely associated with the interrenal tissue. Ultrastructure examination confirmed the existence of two main chromaffin cell types, distinguished by different types of secretory granules. The first type was characterized by the presence of vesicles with round, strongly electron dense core granules, which were eccentrically located. Such cells were interpreted as noradrenaline cells. Meanwhile, cells with vesicles that were completely electron lucent or containing small less dense eccentric granules were identified as adrenaline cells. Many unmyelinated nerve axons emerged from nerve bundle invading the clusters of chromaffin cells. Nerve endings were invaginated into the chromaffin cells through synaptic junctions.
Interrenal tissue consisted of nests, cords or strands of cells in contact with the PCV and interposed with haemopoietic tissue.
Ultrastructure analysis has revealed only one interrenal cell type, which contains abundant smooth endoplasmic reticulum (sER) and numerous mitochondria with tubulo-vesicular cristae, characteristics of steroid-producing cell. The interrenal tissue cells have different cytological aspects that can be linked to a steroidogenic cell cycle allowing a periodical renewal of organelles.