DNA fragmentation in programmed cell death in nucleate erythrocytes: A cytochemical analysis

The frequency and responsiveness to the TUNEL assay were used to compare th e DNA fragmentation associated with programmed cell death in erythrocytes o f the circulating blood from chickens, pigeons, bullfrogs and tortoise spec ies in which the life span and/or metabolic activities of these cells vary considerably. While most avian and adult bullfrog erythrocytes gave a posit ive response in this test, only 31% of the tortoise erythrocytes showed a p ositive TUNEL response, which was generally weak. The strongest positive re sponse was seen in bullfrog erythrocytes. The positive results for avian er ythrocytes may possibly be associated with their higher metabolic rate and body temperature while the lower response for tortoise erythrocytes may ref lect the very long life span and lower metabolic rate of these cells. Based on previous literature reports, the results for the bullfrog are unlikely to be associated with the animal metabolic rate and do not necessarily indi cate genomic inertness. Together with literature data showing divergent pat hways for programmed cell death in erythrocytes, the differences in DNA fra gmentation reported here indicate that further studies on vertebrate nuclea te erythrocytes are required for a better understanding of cell death in th ese cells.