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Prepped by Ollie Stewart 

Document Number: 

97)11-1-311 

Docket Number: 

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Printed 4/18/2008 9:58:25 AM Sheet 97 of 182 
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£>- T-A-H-CJ' 

58 

FF \ «'. A DOCKET 

—A-N—UtTRA'STRUCTURAL STUDY OP THE EFFECTS OF LEAD IN THE 

CENTRAL NERVOUS SYSTEM OF THE RAT. 

H. Reyners, S.Gianfelici de Reyners and J.R.Maisin 

ABSTRACT t The glial balance is highly sensitive to lead intoxication, 

at least in 3 month old female rats, where doses as low as 100 ppm 

Pb given in food ( from bith ) can cause an increasein density of 

astrocytes and microglia compensated by a reduction of oligodendrocytes. 

INTRODUCTION t Lead is a powerful environmental toxic and its deleterious action on the nerve matter has often been reported. The poisonous 

* 

effect has generally been admitted to be due to a specific injury on 

vascular elements (ref 1). Nevertheless, this can be questioned because 

of the very high toxie levels assayed in current neuropathological research (refs 2 & 3). Indeed, we have recently noted that relatively 

mild doses can even produce hypervascularization in the cerebral cortex of the rat possibly in relation with a severe involution of the 

neuropile (ref 4) . In the present work, significant quantitative parenchymal modifications are revealed after very low level lead poisoning. 

MATERIAL & METHODS : Experimental lead encephalopathy is produced in 

rats by means of the Pentschew & Garro model (ref 1) but with the use 

of lower lead levels. Capillary and glial densities are evaluated in 

rat brains by morphometric methods (refs 4 & 5)« 

RESULTS & DISCUSSION : Capillary density although increased in mild 

intoxication ( 10000 ppm Pb in food ) does not reach the control 

level in 100 ppm lead treated rats. These variations appear correlated 

to the cortex thickness changes ( fig 1 ). Indeed, the product of capillary density by cortex thickness remains constant in the used dose 

range ; this indicates that the absolute number of cortical capillaries 

is not modified by lead. The changes in cortex parenchyme were thus 

considered as the independent variable of the system. In this paper, 

our interest is then focused on glial cells which appeared to be much 

more sensitive than previously supposed (ref 6), although in a sex 

-F 

P 

F 

p^~4. ~^ J iP-i... J ^„ tT..Auc^;w,» ^ p w Gnv ^ T ^ -»J ^ n..iiinA m m 
P.3 

59 

TABLE I 

Pb++ 

dose 

in 

ppm 

100 

1000 

5000 

10000 

Female Male 

Glial 

type 

A 

0 

M 

TOT: 

A 

0 

M 

TOT: 

A 

0 

M 

TOT: 

A 

0 

U 

TOT: 

A 

0 

M 

TOT: 

C 

495 

393 

109 

997 

449 

374 

107 

930ns 

533 

339 

125 

997s 

580 

344 

217 

S 

91 

92 

44 

74 

103 

37 

78 

84 

58 

84 

97 

115 

1141SSS 

450 

268 

215 

74 

63 

101 

933SSSBS 

+ 

+ 

+ 

+ 

4 

+ 

+ 

4 

4 

+ 

+ 

-t 

+ 

+ 

4 

4 

NS 

404 

301 

65 

375 

271 

70 

455 

255 

67 

496 

247 

102 

376 

205 

114 

£s 

18.4 

23.4 

40.4 

16.5ns 

27.5ns 

34.6ns 

14.6ns 

24.8ns 

46.4ns 

14.5s? 

28.2ns 

53.0s 

16.4ns 

23.5ns 

47.0 ns 

C 

481 

281 

118 

880 

469 

301 

114 

884ns 

425 

340 

113 

878ss 

545 

345 

190 

1080s 

S 

65 

73 

56 

72 

76 

60 

57 

'96 

45 

87 

84 

90 

+ 

4 

4 

4 

4 

4 

4 

4 

4 

4 

4 

4 

4 

NS 

416 

208 

62 

397 

225 

54 

368 

244 

68 

458 

261 

100 

*s 

13.5 

26.0 

47.5 

15-4ns 

25.3ns 

52.6ns 

13.4ns 

28.2ns 

39.8ns 

• 6.0ns 

24.4ns 

47.4ns 

;•! 

Table I : Effects of Lead and Sex '^n the Glial Balance in the rat at 

3 month old. The total of glial cells ( TOT: ) is subdivided into 

its 3 components : astrocytes (A), oligodendrocytes (0) and microglia (K). For each of these cell populations (C), satellite (S) and 

no satellite cells are counted and the percentage of satellitism 

estatlished. The significance of the desequilibriums between control 

and treated populations is estimated through a 2-way G test. 

dependent way. A G-test analysis of the glial balance between astrocytes, oligodendrocytes and microglia is able to reveal significant 

changes (table I) in their equilibrium. The oligo behaviour is sexlinked : these cells appear to be much more sensitive in female rats, 

a fact which can be correlated to the often reported major lead sensitivity of female individuals. Satellitism for nerve cells is also 

quantitatively evaluated but is not found very modified as in the 

case of x-irradiated brains ( Reyners et al., in prep.). 
60 

2-

1 -

cortex thickness, 

(mm) 

<t> -^ — r 

$9 

capillary density. 

(nVmm*) 

C

^^\ 4 

*~ " ^J ^^ 

**0.tSS*S '""• 

probability ot eurvn: br two *mr MOM . 

of pointt: by t Int. • P> 0.J5 

•• P; ait 

dose P&* 

T'SOO 

250 

10 100 1000 10000 ppm 

Fig 1 : The variations of capillary density in lead treated cortex 

are correlated to the changes in the cortex thickness. 

300 -f 

20U + 

100 + 

Glial density 

(n'/mm*) 

Microglia. 

CO dose Pb " 

10 too 1000 10000 PPm 

Fig 2 I Evolution of the glial populations in the cerebral cortex 

of rats intoxicated with various doses of lead acetate 

and observed at 3 month old. The effect of treatment is 
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61 

In conclusion, the present report shows that vascular elements are 

not the major and only factor at risk in experimental lead encephalopathy. Moreover, the significant glial population changes revealed 

here at doses which do not promote any visible vascular trouble pinpoint the glial nerve supply as a real target of heavy metals and 

consequently as a source of potential damage to brain function 

( ref 7). 

REFERENCES 

1. A Pentschew and F Garro, Acta Neuropath £,266 (1966) 

2. R A Clasen, J F Hartman, J A Starr, P S Coogan, S Pandolfi, I 

Laing, R Becker and G M Hass, Am J Path 74., 215 (1974) 

3. A D Toews, A Kolber, J Hayward, M R Krigman and P Morell, 

Brain Res 147, 131 (1978) 

4. H Reyners, E Gianfelici de Reyners and J R Maisin, Experientia 

32., 1416 (1976) 

5. D W Vaughan and A Peters, J Neurocytol 3_, 405 (1974) 

6. D V Markov and R N Dimova, Acta Neuropath _2j3, 25 (1974) 

7. G Winneke, A Brockhaus and R Baltissen, Arch Toxicol ^7., 247 

(1977) 
P.6 

<ZCSiQafOO "7 

UNITED STATES GOVERNMENT PROPERTY 

This book is the property of the United States 

Government Environmental Protection Agency. 

International Conference 

Management & Control of 

HEAVY METALS 

in the 

ENVIRONMENT 

London - September 1979 

Co-sponsors 

Commission ofthe European Communities Institution of Water Engineers & Scientists 

Institution of Public Health Engineers Institute of Water Pollution Control 

World Health Organisation