Photodynamic action and chromosomal damage: a comparison of haematoporphyrin derivative (HpD) and light with X-irradiation.

Chromosomal aberrations (CA) are induced in human cells (NHIK 3025) in vitro when exposed to X-rays and to haematoporphyrin derivative (HpD) plus light. At the 0 . 1 survival level X-rays induce about 10 times more breaks per chromosome than the photodynamic treatment. There is some evidence for non-random distribution of the CA induced by HpD plus light; i.e. they seem to be localized at the centromeric and telomeric regions. Such non-random distribution of CA could be explained if centromeric and telomeric chromatin were associated with the inner nuclear membrane.