Interactions of nitrilotriacetic acid (NTA) with Cr(VI) compounds in the induction of gene mutations in cultured mammalian cells

The Science of the Total Environment, 71 (1988) 567 Elsevier Science Publishers B.V., Amsterdam - - Printed in The Netherlands

INTERACTIONS

OF N I T R I L O T R I A C E T I C

D U C T I O N OF G E N E M U T A T I O N S

L. CELOTTI,

D. FURLAN,

ACID

IN C U L T U R E D

L. SECCATI

(NTA)

WITH Cr(VI)

MAMMALIAN

and A.G.

COMPOUNDS

567

IN THE

IN-

CELLS

LEVIS

D e p a r t m e n t of B i o l o g y U n i v e r s i t y of Padua Via L o r e d a n i0 35131 Padua - Italy

Data c o n c e r n i n g the m u t a g e n i c i t y of N T A are c o n t r a d i c t o r y b u t the w e i g h t of e v i d e n c e i n d i c a t e s that, a l t h o u g h N T A is not a v e r y strong mutagen, it is not c o m p l e t e l y l a c k i n g genotoxicity. W i t h r e g a r d to the p r o d u c t i o n of gene mutations in mamanalian cell systems, until now N T A was found inactive in mouse l y m p h o m a cells c u l t u r e d in vitro (induction of m u t a t i o n s at the TK locus), b u t a c t i v e in h u m a n cells c u l t u r e d in vitro (induction o f r e s i s t a n c e to the d i p h t e r i a toxin). We used the V79 C h i n e s e h a m s t e r cell line to d e t e c t the i n d u c t i o n of 6-thioguanine resistance, due to m u t a t i o n at the H G P R T locus, w i t h d i r e c t (methylmethanesulphonate) and i n d i r e c t (dimethylnitrosamine) m u t a g e n s as p o s i t i v e controls. N T A was t e s t e d w i t h i n a range of 10 -4 - 1.5xi0 -2 M concentrations: a l t h o u g h it was c y t o t o x i c above the 10 -2 M dose, it did not increase the freq u e n c y of m u t a t i o n s at any o f the tested c o n c e n t r a t i o n s , i n d e p e n d e n t l y of metabolic a c t i v a t i o n (rat liver S-9 m i x system). On the o t h e r hand, N T A is known to solubilize h e a v y m e t a l s and, therefore, to i n c r e a s e their genotoxicity. Here we found that an insoluble Cr(VI) compound, l e a d c h r o m a t e (PbCrO4), w a s not c y t o t o x i c nor m u t a g e n i c o n V79 cells, p r o b a b l y b e c a u s e it is taken up b y the cells v e r y slowly, w h e r e a s the p r e s e n c e o f N T A (2.5xi0 -3 M, in water) e l i c i t e d a d i r e c t c y t o t o x i c i t y and mutagenicity, w h i c h was d o s e - d e p e n d e n t w i t h i n a range of 10 -6 - 10 -4 M P b C r O 4. This e f f e c t w a s due to s o l u b i l i z a t i o n by N T A of c h r o m a t e anion, as d e t e r m i n e d by c o m p a r i n g s p e c t r o p h o t o m e t r i c d e t e r m i n a t i o n s o f Cr(VI) in P b C r O 4 t r e a t m e n t solutions w i t h a m u t a g e n i c i t y t i t r a t i o n curve o b t a i n e d w i t h a c o m p l e t e l y soluble Cr(VI) salt (potassium dichromate, K2Cr207).

S u p p o r t e d b y CNR, Full p a p e r

P.F.

published

"Medicina

Preventiva

e Riabilitativa".

in Murat. Res., 190 (1987) 35-39.