Comparative patterns of hepatic drug metabolizing enzymes and their possible correlation with chromosomal aberrations in transplantable murine lymphoma: a time course study

Anticlastogenic potential of 1alpha,25-dihydroxyvitamin D3 in murine lymphoma

Vitamin D3, having gained scientific interest for so long because of its role in mineral homeostasis, has now received great importance as a possible antitumor agent. This study was undertaken in an attempt to visualize the possible anticlastogenic potential of the vitamin in an ascitic mouse lymphoma model namely, Dalton's lymphoma. Frequencies of structural type chromosomal aberrations, sister chromatid exchanges and micronucleus assays have been chosen as the genotoxic endpoints in the proposed investigation. All these cytogenetic markers have been found to be markedly elevated during the progression of lymphoma in bone marrow cells. Vitamin D3 effectively suppressed the frequencies of chromosomal aberrations and sister chromatid exchanges in the lymphoma-bearing mice during the entire phase of tumor growth that significantly coupled with almost two-fold increase in survival time (37 +/- 2 and 68 +/- 2 days in lymphoma controls and vitamin D3-treated lymphoma-bearing mice, respectively), thus substantiating the antineoplastic efficacy of this secosteroid. The outcome of this study also is clearly reflected in the depletion of circulating (serum) vitamin D3 levels in the lymphoma control mice compared with normal (vehicle) controls while a still higher level was maintained in the VD3-treated lymphoma mice. This anticlastogenic property of the vitamin has so far been neglected and this is the first attempt to unravel the vitamin D3's effect in combating tumor development in vivo by limiting the frequencies of chromosomal aberrations, sister chromatid exchanges and micronuclei at least in transplantable murine model studied herein.

Alterations in total iron, zinc, and calcium levels and their influence on the hepatic activities of gamma-glutamyl transferase and glucose-6-phosphatase in the host bearing transplantable murine lymphoma

The levels of iron, zinc, and calcium in liver as well as serum, together with the enzymatic activities of gamma-glutamyl transferase (GGT, EC 2.3.2.2) and glucose-6-phosphatase (G-6-Pase, EC 3.1.3.9) in liver, were critically monitored over various periods in male Swiss albino mice bearing Dalton's lymphoma (DL), a transplantable ascites-producing tumor. Both hepatic and serum contents of iron, zinc, and calcium were found to be maximally elevated (p < 0.001) on day 15 after tumor transplantation as compared with their contents in normal animals. There was a gradual increase in the activity of GGT in liver in lymphoma-bearing mice in comparison with their normal counterparts, which showed a maximum peak (p < 0.001) on day 15, followed by a continuous and sharp fall. Hepatic G-6-Pase activity was found to decrease continuously throughout the progression of lymphoma as compared with its levels to normal animals. Tumor-cell counts in peritoneal lymph fluids of mice containing DL yielded a maximum count of 155.7 x 10(3) cells/mm3 on day 15. A significant correlation was observed among the levels of different metals, enzymatic activities, and tumor-cell counts at different periods of study. From these results, it can be concluded that the metals studied may have a role in initiating and controlling cellular proliferations, through their effects on modulating the activities of the possibly preneoplastic and neoplastic marker enzymes named above.

Cadmium-induced alterations of hepatic lipid peroxidation, glutathione S-transferase activity and reduced glutathione level and their possible correlation with chromosomal aberration in mice: a time course study

Cadmium, a heavy metal, has been found to possess a potent toxic effect on liver and bone marrow. In the present study, attempts were made to understand whether or not any correlation existed between hepatic lipid peroxidation, glutathione S-transferase activity, reduced glutathione level and chromosome aberrations, micronucleus and mitotic index in bone marrow cells of Balb/C male mice. Cadmium chloride (2.5 mg/kg b.wt.), when administered subcutaneously for 7 alternate days, exerted duration-dependent toxic effects on hepatic biochemical and cytogenetic parameters of bone marrow. A shorter time interval (5 days) elicited no significant alteration in the case of biochemical parameters, but with the advancement of time (i.e. after 10 and 15 days) lipid peroxidation showed 102% (p < 0.001) elevation and after 15 days, glutathione S-transferase activity and reduced glutathione level decreased by 35%, (p < 0.001) and 32% (p < 0.001), respectively, from the control values with concomitant elevation of chromosomal aberrations (30%) and micronucleus (2.32%) but the mitotic index was inhibited by 1.26%. The results of our study, provided evidence of cadmium-induced duration-dependent depression of GSH-mediated GST-catalysed detoxication capacity of the host and that this was presumably related to the induction of chromosomal aberrations. The clastogenic efficacy of this heavy metal was thus evident from the study.

Beta-carotene inhibits rat liver chromosomal aberrations and DNA chain break after a single injection of diethylnitrosamine

Beta-carotene (BC) has recently been found to possess potent anti-tumour activity in chemically induced rat liver carcinogenesis. In the present study, attempts have been made to understand the basic cytogenetic and molecular mechanism of the anti-tumour effect of BC by monitoring its effect on rat liver chromosomal aberrations (CAs) and DNA chain breaks during the early preneoplastic stage of diethylnitrosamine (DEN)-induced hepatocarcinogenesis in male rats. DNA chain breaks, however, can be detected with great sensitivity by exposing crude cell lysates to alkaline solutions and monitoring the rate of strand unwinding so that one strand break per chromosome can easily be detected. Supplementary BC, in basal diet (120 mg kg[-1]), was given to rats 15 days before carcinogenic threat with DEN. Under these experimental conditions, BC was found to afford a unique protection against DEN-induced CAs 96 h after DEN injection. Long-term treatment with BC also triggered a protective effect on induction of CAs 15, 30 or 45 days after DEN treatment, which was maximal on structural aberrations followed by numerical and physiological types. BC treatment for 15 days before DEN injection was found to offer a significant (P < 0.001) protection in the generation of single-strand breaks compared with DEN control. Thus, BC ranks as a potential chemopreventive agent for the future so far as chemical rat liver carcinogenesis is concerned.

Role of beta-carotene on the changes in activity patterns and levels of biotransforming enzymes in transplantable murine lymphoma

The differential levels of induction of hepatic microsomal cytochrome P-450 (cyt. P-450), UDP-glucuronyl transferase (UDPGT) and cytosolic glutathione-S-transferase (GST) activities were evaluated over various periods of time, following tumor transplantation in male Swiss albino mice in the presence and absence of beta-carotene supplementation in their basal diet (100 mg/kg). An increase in the total hepatic microsomal cytochrome P-450 and UDP-glucuronyl transferase and cytosolic GSH-transferase activities (1.5 to 2 fold) occurred during the later stage of tumor progression (22 +/- 2 days onwards). However, beta-carotene supplementation throughout the study increased or decreased the random activity trends of the above markers significantly (P < 0.05- < 0.01). Finally, beta-carotene supplementation could enhance the survival of the host bearing lymphoma by almost 2-fold (50-60 days) over and above the lymphoma controls (30-35 days).