Histochemical and experimental study on the adrenal of the freshwater catfish, Ompok bimaculatus (Bloch).

The adrenal tissue is situated around the cardinal vein and its branches in the pronephric head kidney. The medullary cells are largely confined to the wall of these blood vessels whereas the cortical cells are arranged in several layers around the medullary cells. The cortical cells are eosinophilic and give positive reaction to sudan black-B, Baker's acid haematein and Schultz's tests. In response to ACTH and thiourea treatments the cortical cells exhibited hypertrophy, degranulation and depletion of lipid content. Pronounced cortical atrophy was evident in the hypophysectomised specimens. Marked involution was noticed in the cortical cells in response to hydrocortisone treatment. The medullary cells are larger than the cortical cells and are eosinophobic. They give positive reaction to ferric-ferricyanide, PAS and ascorbic acid tests. Two types of medullary cells could be differentiated with the help of dichromate, iodate and glutaraldehyde-silver techniques. These cells did not exhibit any visible change after ACTH, hydrocortisone and thiourea treatments. However, reduction in the cellular size is obvious in the hypophysectomised fish.