Aflatoxin B-1-induced micronuclei and cell cycle alterations in lung and bone marrow cells and their modulation by Piper argyrophyllum extract

Aflatoxin B-1 (AFB(1)) is a clastogen that causes cellular damage by covale nt modification of nucleic acids. In this investigation, male rats were inj ected i.p. with AFB(1) (8 mg/kg b.w.) in DMSO and the same dose of AFB(1) w as also administered intratracheally (i.t.) to the animals separately. The animals were killed after 26 h of the carcinogen treatment, femur bone was removed, and bone marrow cells were isolated and stained with Mayer's hemat oxylin and eosin. Micronuclei (Mn) were scored by using light microscopy. B ronchoalveolar lavage (BAL) was prepared from rats administered AFB(1) i.t. A part of BAL was fu;ed with 70% ethanol, stained with the fluorochrome DA PI, and analysed for cell cycle variations; the other part of the lavage wa s used for making slides to record Mn with a fluorescent microscope. A sign ificantly greater proportion of lung cells were found to enter cell cycle w ith extended S-phase due to AFB(1) treatment. Mn were induced in polychroma tic erythrocytes (PCE) as compared to normochromatic erythrocytes (NCE) in the bone marrow of AFB(1)-treated rats, where there was nearly a three-fold increase in the number of Mn of bone marrow cells. The administration of A FB(1) resulted in a two-fold rise in the Mn in the lung cells. The effect o f BSO, DEM, and PB, the modulators of AFB(1) metabolism, was studied on AFB (1)-induced Mn formation. A significant increase in the Mn score in PCEs of BSO- and DEM-treated rats was noted, while a slight reduction in the Mn sc ore was noted in the case of PB-treated rats. The administration of the met hanol extract of the leaves of Piper argyrophyllum (taken up in DMSO) to ra ts for a week exhibited normalising effect on AFB(1)-induced Mn in bone mar row cells. These observations record the induction of Mn in lung cells due to AFB(1) for the first time. We propose the utility of AFB(1)-induced Mn a s a model for screening plant extracts as inhibitors of genotoxicity. Preve ntion of genotoxic changes described above by phytochemicals is being pursu ed in our Laboratories. (C) 1998 Wiley-Liss, Inc.