The present study was performed to evaluate an overall effect of long-term consumption of excessive fluoride (F) amounts by rats on their erythrocytes. The animals were administered regular drinking water (0.4 ppm F) or the same water supplemented with 2, 10, and 20 ppm F (as NaF) for 12 months. Chronic exposure of the rats to increasing F doses induced a progressive rise of the plasma F concentration accompanied by a dose-dependent fall of hematocrit and decrease in the mean erythrocyte volume. Consumption of 10 and 20 ppm F resulted in appearance of morphologically abnormal cells (stomatocytes and echinocytes) in the peripheral blood. Rise of the water F concentration to 20 ppm F led to significant increase in the number of phosphatidylserine-exposing erythrocytes, although suppression of cell viability was revealed in all three groups of F-poisoned rats. A compensatory enhanced release of reticulocytes was not sufficient to compensate for erythrocyte loss. Dose-dependent accumulation of free cytosolic Ca(2+) appears to be a major pathophysiological process underlying the development of F-induced death processes in rat erythrocytes. In addition, 10 and 20 ppm F induced ATP depletion and generation of peroxides in erythrocytes, whereas superoxide and glutathione levels were not altered. Thus, long-term intoxication of the rats with F triggers premature death of their erythrocytes due to intrinsic death-associated biochemical defects and development of anemia.