@Copyright 1991 by The Humana Press, Inc. All rights of any nature, whatsoever, reserved. 01634984/91/3102-0139 $02.00

Modification of Cesium Toxicity by Calcium in Mammalian System

ADITI GHOSH,* ASIS KUMAR GHOSH, ARCHANA SHARMA,

AND GEETA TALUKDER

Genetic Toxicology Unit, Centre of Advanced Study in Cell and Chromosome Research, Department of Botany,

University of Calcutta, 35, Ballygunge Circular Road, and Vivekananda Institute of Medical Sciences, Calcutta 700 O19, India

Received January 25, 1991; Accepted February 15, 1991

ABSTRACT

The interaction between cesium chloride CsC1 and calcium chlo- ride CaCI2 was observed in bone marrow chromosomes of mice. The two salts were administered orally to laboratory bred Swiss albino mice in vivo singly or one followed by the other, or both simul- taneously. CsC1 induced chromosomal aberrations in frequencies di- rectly proportional to the dose administered. The frequency of aberra- tions was reduced significantly when the two chemicals were administered simultaneously or when CaC12 was given 2 h before CsC1. Thus, CaC12 is able to protect against the cytotoxicity of CsC1.

Index Entries: Cesium chloride; calcium chloride; clastogenecity; chromosomal aberrations; cesium---calcium interaction.

INTRODUCTION

Cesium, an alkali metal of Group IA, is p resen t in trace amoun t s in vegetables and animal tissues. It has primarily been s tud ied because of its effects on enzyme activation, toxicological problems related to its uptake a n d passage th rough food chains, and its applicat ion as a phar- macological agent (I). Ces ium is toxic to m a n y plants (2), mice and rats (3,4) and h u m a n s (5). At tempts have been m a d e to modi fy the clasto-

*Author to whom all correspondence and reprint requests should be addressed.

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140 Ghosh et al.

genic effects of cesium using vitamins (6) and plant products (7) that have yielded promising results.

The roles of interaction between metals in modifying the clastogenic action, e.g., Pb by Se (8), Hg by Se (9), Cd by Se (10), A1 by Ca (11), and Co by Ca (12) have been worked out in our laboratory and have shown positive results. Metals usually occur in combination and hence, these studies are of considerable importance (13). Since no information is available about the effect of Ca-Cs interaction at the level of cell and chromosome division, the present work was undertaken to study the modifications induced by calcium on the effects of cesium in bone mor- row cells of Mus musculus.

MATERIALS AND METHODS

Laboratory bred Swiss albino female mice (Mus musculus, 2n = 40), about 8-10 wk old, weighing 25--30 g with adjustment in the calibration of weight of animals and administration (to give the same dose&g) were used. The mice were housed in polycarbonated cages with filter tops. Ambient temperature (20 + 5~ relative humidity (50 + 15%), and photoperiod (12 h) were maintained throughout the study. The animals had access to standard pellet diet (Gold Mohur mice feed manufactured by Lipton India Limited) and water ad libitum. Two concentrations (125 mg and 250 mg/kg body wt) of cesium chloride (CsC1; Sisco Laboratories, India) and calcium chloride (CaCIa-2H20, Sarabhai M. Chemicals, India) were prepared in distilled water. The two solutions were orally adminis- tered by gavage to mice in vivo, according to Table 1. Five mice were used for each treatment set. Control sets were maintained for each set of treatment.

Two hours prior to sacrifice, mice were intraperitioneally injected 4 mg/kg body wt of colchicine. All the animals were sacrificed after 24 h by cervical dislocation and the bone marrow was flushed out and prepared for chromosomal analysis following the usual hypotonic-acetic acid:eth- anol fixative--Giemsa staining schedule (14). Slides were subsequently coded and scored blind for chromosomal aberrations.

For chromosomal aberrations, 50 metaphases/animal, making a total of 250 plates/treatment set were scored. Aberrations were scored from good scattered metaphases without overlapping of chromosomes. Indi- vidual aberrations were recorded separately. All aberrations (chromatid and chromosome gaps, chromatid and chromosome breaks, rearrange- ments) were considered equal, regardless of the number of breaks in- volved (15). Percentage of aberrant metaphase cells (excluding gaps) and number of breaks per cell were calculated. To determine the effective modulating dose for chromosomal aberrations, comparison between each treatment group and the control was made using the Student's t-test. A one-way ANOVA (16), followed by Duncan's multiple-range

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Cesium Toxicity 141

Table 1 Experimental Protocol

Experimental Concentrations mg/kg Treatment chemicals set body wt

Distilled water alone (control)

CaC12 �9 2H20

A

B

CsC1 C

CsCI followed by CaCI2 after 2 h D

Simultaneous feeding of CaC12 + CsCI E

CaCI 2 CsCI

B1 125 - -

B 2 250 - -

C1 - - 125

C2 - - 250 D1 125 125

D2 250 250 E1 125 125

E2 250 250

test (17), was used with the help of Harter's table (18) to detect significant differences among the different treatment groups.

RESULTS AND DISCUSSION

The endpoint for screening was the frequency of chromosomal aber- rations, which included breaks, acentric fragments, dicentrics, gaps, and polyploids. The frequencies of chromosomal aberrations induced were significantly higher in the animals given CsC1 (D1 and D2) than in the controls. This enhancement was linearly dose-dependent and statis- tically significant at p - 0.05 level. The positive clastogenic effects of CsC1 had been observed earlier in our laboratory (3).

A combination of CaC12"2H20 and CsCI reduced significantly the level of clastogenicity of the latter, when the two chemicals were administered simultaneously, (E 1 and E2) by gavage. Administration of CaC12"2H20 2 h before exposure to CsC1 also reduced significantly the frequency of chro- mosomal aberrations. Both combinations (D and E) could reduce chro- mosomal aberrations effectively (Table 2). CaC12-2HaO was ineffective when it was given after CsCI.

Analysis of the results by one-way ANOVA, followed by the Dun- can's multiple range test, showed that the protection afforded by CaC12"2H20 against the clastogenic effects of the lower dose of CsC1 (125 mg/kg body wt), though significantly higher than the control, was not significantly different between the animals given CaC12.2H20 before (D1) and those given the chemicals simultaneously (E0 (Tables 3, 4). The results obtained with the higher dose of CsCI is similar to the lower dose,

Biological Trace Element Research I/ol. 31, 1991

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Biological Trace Element Research VoL 31, 1991

Cesium Toxicity

Table 3 Chromosomal Aberrations Induced in Female Mice by the Lower Dose of CsC1 [ANOVA (One-Way)]

143

Degrees of Mean sum freedom, Sum of of squares,

Source of variation df squares, SS MSS F

Between groups 4 353.2 88.3 18.62" Within groups 20 94.8 4.74 - -

*Highly significant; level of significance, p = 0.05.

Table 4 Chromosomal Aberrations Induced in Female Mice

by the Lower Dose of CsCI [Duncan's Multiple-Range Test]

Experimental set A E1 B1 D1 C1

Sample mean* 1 3.8 5.8 6 12.4

*The straight lines denote that there is no significant difference between the groups at p = 0.05.

Table 5 Chromosomal Aberrations Induced in Female Mice

by Higher Dose of CsC1 [ANOVA (One-Way)]

Source df SS MSS F

Between groups 4 583.6 145.9 95.98* Within groups 20 30.4 1.52 - -

*Highly significant; level of significance, p = 0.05.

Table 6 Chromosomal Aberrations Induced in Female Mice

by Higher Dose of CsC1 [Duncan's Multiple-Range Test]

Experimental set A E2 B 2 D2 C2

Sample mean* 1 6.4 6.6 7 16

*The straight lines denote that there is no significant difference between the groups at p = 0.05.

a l though the p ro tec t ion a f fo rded is less (Tables 5, 6). Thus , the m o d e of p ro tec t ion is t h r o u g h the act ion of Ca on the cellular s y s t e m s ra ther than t h rough b ind ing wi th Cs + .

Cs + can act as an ana log of po ta s s ium, a nutr i t ional ly essent ia l e lement , a n d t hus can be potent ia l ly ha rmfu l (19). It can activate N a + / K +- d e p e n d e n t ATPases in the absence of K + (20-23) , and is t r a n s p o r t e d into the cells via p a t h w a y s sensi t ive to ouaba in inhibi t ion (24,25). It also

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144 Ghosh et al.

blocks vo l t age -dependen t channels that normal ly conduc t Na + or K + ions (26). The only informat ion on the interact ion be tween Cs and Ca is that Ca is capable of reversing antimicrobial effects of Cs + (27).

The assimilat ion of Cs by plants and animals, coupled wi th its efficient transfer th rough food chains to h u m a n s , and depos i t ion in muscle and o ther tissues, makes it an impor tan t e l emen t f rom a tox- icological s tandpoin t . Hence, the use of o ther cations like Ca 2+ can be a posi t ive way to decrease the cytotoxic effects of ces ium in living systems.

A C K N O W L E D G M E N T S

The authors are grateful to the Universi ty Grants Commiss ion and Counci l of Scientific and Industr ial Research, New Delhi for financial assistance and to A. K. Sharma, P rog ramme Coordinator , Centre of A d v a n c e d S tudy in Cell and C h r o m o s o m e Research, Depa r tmen t of Botany, Universi ty of Calcutta for facilities and encouragement .

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Cesium Toxicity 145

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