Environmental regulation of the function of circulating erythrocytes via changes in age distribution in teleost fish: Possible mechanisms and significance.

The blood of fish has a continuous age distribution of erythrocytes. The properties of young and old erythrocytes differ with young erythrocytes being functionally much more versatile than old erythrocytes, which have higher haemoglobin content. Factors which affect the formation and breakdown of erythrocytes are reviewed. Erythropoiesis in fish is largely similar to that in mammals. However, definitive erythrocytes are mainly formed in the anterior part of the kidney, and erythropoietin is secreted mainly from the heart. Senescence of erythrocytes in fish has not been studied in detail, and consecutively the factors causing aging of erythrocytes in man are discussed. A major factor causing aging of erythrocytes is oxidative stress, which is also a major effect of toxicants on fish erythrocytes. Consequently, apparent age distribution of circulating erythrocytes will be affected by environmental pollution. At present, it is completely unknown, if the changes in age distribution of erythrocytes play a role in pollutant responses or if the age distribution of erythrocytes is actively regulated during environmental adaptation.
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