The Cells with Intracytoplasmic Calcium-rich Granules in the Kidneys of Salmonid Fishes

Abstract

The head kidneys of salmonid fishes, which had a unique dark brown color, were examined electron microscopically and were found to have a large number of cells with round to oval intracyto-plasmic electron-dense granules (EDG; 150-450nm in diameter) in hematopoietic tissue. Most of these cells were round-shaped with a peripherally located nucleus rich in chromatin. The EDG were surrounded by membrane structure. X-ray microanalysis showed that these granules contained a large amount of calcium when compared with other electron-lucent cytoplasm. By atomic absorption study, the calcium contents of kidneys in two salmonid fishes, rainbow trout Salmo gairdnerii and coho salmon Oncorhynchus kisutch, were significantly higher (150-190μg/g-tissue) than those of liver and spleen (56-108μg/g-tissue) in the same species and those of kidneys, liver, and spleen (59-114μg/g-tissue)in carp Cyprinus carpio.