Co-occurrence of acrocentric chromosome associations with dicentric chromosomes in irradiated human lymphocytes.

PURPOSE: The occurrence of acrocentric chromosome association (ACA) after radiation exposure is an interesting cytogenetic endpoint, known to show a dose-dependent increase in irradiated lymphocytes suggesting its potential use in radiation biodosimetry. Here, an attempt was made to study the complexity and correlation of the occurrence of ACA with dicentric chromosomes (DC) in lymphocytes exposed to gamma radiation.

METHODS: Ninety metaphases each with DC and without DC were chosen randomly from lymphocytes irradiated with different doses (0, 1, 2, 3, 4 and 5 Gy) of gamma radiation. ACA along with chromosomal types of aberrations were scored and analyzed for complexity and co-occurrence, retrospectively.

RESULTS: The number of associations between 2 and ≥ 3 acrocentric chromosomes showed an increase with each irradiation dose. Concomitantly, the total number of chromosomal type of aberrations showed an increase in number at each radiation dose studied. The number of DC showed an increase, however, metaphases containing 1DC decreased while ≥ 2DC increased as the radiation dose increased. The number of tricentric chromosomes increased at doses higher than 2 Gy. Importantly, the association of DC with an acrocentric chromosome was noticed at doses 2 Gy and above. A significant (p < 0.05) increase was noticed in ACA frequency in 1DC and ≥ 2DC metaphases at 1 and 2 Gy, in 1DC at 3 Gy, and in ≥ 2DC 4 and 5 Gy compared to the frequency in no DC metaphases. When average ACA frequency was plotted against DC frequency, a significant (p = 0.0009) correlation was observed, producing regression equation y = 0.9025x + 0.1283; R2  = 0.9522.

CONCLUSION: The present analysis showed increasing ACA complexity with increasing radiation dose. Furthermore, a higher frequency of ACA in cells with 1DC or ≥ 2DC compared to the ACA in cells without DC from the same sample of irradiated lymphocytes demonstrated the co-occurrence of ACA and DC in the same cells.