The adrenal chromaffin cells of Salmo gairdneri Richardson (Teleostei, Salmonidae).

The chromaffin cells of the adrenal homologue of Salmo gairdneri R. have been studied by light and electron microscopy. The chromaffin tissue was localised in the head kidney adjacent to the wall of the proximal part of the cardinal veins and their main branches. Specific histochemical techniques failed to demonstrate different types of chromaffin cells. With the electron microscope two different types of chromaffin cells were observed. The first type, characterised by numerous dense cytoplasmic granules of average diameter 90 nm, was interpreted as a noradrenalin cell; the second type was characterised by the presence of moderately electron-dense granules of average diameter of 85 nm, and was interpreted as an adrenalin cell. The reaction for acetylcholinesterase activity was present on nerve terminals and sometimes in the vacuolar membrane systems of both chromaffin cells.