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Comparison of the Fate of Vinyl Chloride Following
Single and Repeated exposure in Rats

•Tt1

X

P.C. Watanahe, .J.A. Zompel, P.,1. i 'ehr i ng

R&S 103903

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Toxicology X Applied Pharmacology

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K. R. Smith
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V. K. Rowe
Toxicology Researcii

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P. G. Watanahe
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Toxicology Research

636-1313

Midland

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COMPARISON OF THE FATE OF VINYL CHLORIDE FOLLOWING SINGLE
AND REPEATED EXPOSURE

IN RATS

by
P.

G.

Watanabe,

J.

A.

Zempel

and P.

J.

Gehring

R&S 103904

May 18,

1S77

Toxicology Research Laboratory
Health and Environmental Research
Dow Chemical U.S.A.
Midland, Michigan
48640

COMPAQI V)N OF-' Tin: FAT!: OF VTNY . ntF.niMi'K pou.owrNO
StNCLi: AN!) FFI’FATFD I”-; ’OSURF IN RATS

P.

G.

Watanabc,

J.

A.

Zempol

and R.

J.

Gehring

ABSTRACT

Rats were exposed by
chloride

fate of

6 hours/day,

(VC)

last day of

inhalation

14

5000 ppm nonlabeled vinyl

5 days/week

repeated exposure

the

to

for

7 weeks.

On the

^C-labeled VC was used.

J-VC was compared

in

The

the group of rats exposed

repeatedly to a group exposed simultaneously for a single

6 hour period to 5000 ppm
excretion of

14

mental groups.

14

C-VC.

The routes and rates of

C-activity were the same for the

two experi­

The activity of microsomal enzymes,

as

reflected by aniline hydroxylase and £-nitroanisole £demethylase of 9000 x g liver supernatants was essentially
the same

in rats exposed once,

control rats.

Covalent binding

repeatedly or in nonexposed
to hepatic macromolecules

was greater in rats repeatedly exposed when compared to
those subjected to a single exposure.

These results

that repeated exposure to VC does not induce
formation.

However,

its biotrans­

increase in hepatic macromolecular

that repeated exposure augments

the

reaction of electrophilic metabolites with macromolecules,
and this may be expected

to enhance potential

including carcinogenicity.

toxicity

R&S 103905

binding indicates

the

indicate

r &S 103906

1

-

-

TNTKODUCTION

While many pharmacokinetic and metabolic studies have been
conducted on vinv]

chloride

(VC),

most of

these

tions have concentrated on

the

following single exposure.

Since cancer has

investiga­

fate of VC durinq and
been

induced

by long-term repeated exposure of both experimental animals
and man to VC,

it is

important

to consider alterations in

the disposition of VC in the body which may occur after
repeated exposure.

In preliminary studies monochloroacetic acid was
identified as a major urinary metabolite
exposure

(6 hours/day,

nonlabeled VC

(Hefner,

14

C-VC

(Watanabe,

following repeated

5 davs/week for 9 weeks)

to 5000 ppm

et al.,

this meta­

bolite has not been found
to

tentatively

1975).

However,

ir. rats given ^

et al^. ,

1976).

single exposure

This raised

the question

whether the biotransformation of VC may be altered upon
repeated exposure.

A change in the biotransformation of VC after repeated
exposure is particularly important

in assessing

of exposure

to VC since evidence suggests

metabolized

to a

responsible

for

the hazard

that VC is

reactive metabolite which is ultimately
its

tr'xic manifestations.

This concept is

-2-

supportcd by studies showing an enhancement of
activity of VC

to bacteria when microsomal

enzymes are added
transformation
Rannug,

demonstrated

the

(Bartsch,
et £rl. ,

system to provide
et a_i. ,

1974).

1975) ,

1975),

(Barbin,

transformation of VC is

(1975a)

1975;. Mniavielle,

In addition,

et al_. ,

et a 1. ,

recent reports
in vitro,

to the microsomes

protein sulfhydryl groups,

and adenosine

response was

for metabolic

that liver microsomal enzymes,

the binding of VC metabolites
et a_l.,

and soluble

RNTA

1975) .

involved intimately

mediate

(Kappus,

(Bolt,
That

et al. ,

the bio­

in its toxic

further substantiated when Reynolds,

et al.

showed that acute hepctotoxicity could be produced

by VC if the animals were pretreated with phenobarbetal or
Arochlor 1254,
Reynolds,

inducers of microsomal enzyme activity.

et al_.

(1975b)

also reported that a single 6-hour

exposure to 5% VC deactivates cytochrome P-450 and other
components of the mixed function oxidase system.

Since there is evidence suggesting that repeated exposure to
VC may alter its biotransformation and since the metabolism
of VC

is associated with

its

toxicity,

the objective of th=

current study was to determine whether the

fate of VC is

R&S 103907

1975;

to

the mutaejenic

-3-

indecd altered with repeated exposure.
by exposing rats

to nonlabeicd VC

last exposure to 14C-labeled VC.
was then followed for 72 hours

This was accomplished

for 7 weeks and on the
The

the 14C-VC

fate of

and compared to animals

receiving a single exposure.

METHOD

Material.

Vinyl chloride gas

(Matheson Gas Products)

99.9% minimum purity was used throughout the
labeled VC was synthesized from

prior to use

14

Lot #819-292,

(Wagner and Muelder,

14C)

Re­

1,2-dichloroethana

4.8 mCi/mmole)

1275).

immediatPxy

The synthesized

C-VC has been reported to be 95-96% radiochemically pure

(Wagner,

et al^. ,

3575).

14

was mixed with the *
activity.

(Matheson Gas Products)

C-material to obtain the desired specific

Typically,

mixture was

Nonlabeled VC

40 ml of

injected into a iC

the 14C-VC,

helium gas

liter Saran bag

(Anspec,

Inc.)

containing the desired quantity of nonlabeled VC.

Animals.
tory)
study.

Male Sprague-Dawley rats

with an initial weight of 160-180 g were used
All animals were housed in rooms

humidity,

8 PM)

(Spartan Research Labora­

temperature,

were maintained.

in the

in which a constant

and 12 hour light-dark cycle

(8 AM -

Food and water was provided ad

Iibiturn

R&S 103908

(New England Nuclear,

(1,2

study.

of

-4-

Kxpjr.utc:; wcro conducted

except durinq the L'Xposuro.
9:00 AM and

Exposure.

4:00

711

PM

(KST).

rats were exposed under dynamic conditions

a nominal concentration of
(control)

in 30

7 glass

into the chamber air
pump.

between

5000 ppm VC’

(treated)

inhalation chambers.

flow

(

6

1/min)

to

or icon air

VC was metered

with a dual

syringe

The nominal concentration of VC was determined

from

the ratio of the rate at which the VC gas was dispensed and
the total chamber air flew.

The analytical concentration of

VC was monitored continuously by recirculating a fraction of
the chamber atmosphere through an infrared spectrophotometer
(Wilks)

set at 10.6

...

The rats

were exposed 6 hours/day,
exposures

in

44 days).

repeatedly exposed to VC

5 days/week

for 7 weeks

(32

The mean analytical concentration of

VC over the 7 week exposure period was

4775+908

(SD)

ppm.

On the final day of exposure the animals were subjected to
a b hour exposure

to

14

C-labeled VC generated in the same

manner as described above.

On this

final day of exposure,

vals by gas chromatography,

and at the same

times

the

Re­

activity was determined by bubbling 1 ml aliquots of the
chamber atmosphere into a
Concifluor

scintillation solution containing

(Mai 1inckrodt Chemical),

2-methoxyethanol,

toluene

R&S 103909

the chamber atmosphere was also analyzed at hourly inter­

(6:11:83)

(WuLuriaL><_-,

c_t uj^. ,

determined by counting
meter.

1976).

in a

The mean analytical

The

radioactivity was

liquid scirtiLlation spectro­
concentration determined cn

the

1 final exposure day when the animals were exposed to
labeled VC was 4600 ppm ±
was

311

(SD).

*C-

The specific activity

50 dpm per microgram VC.

The inhalation chamber was operated
to prevent contamination of
transit through the

in a laboratory fume hood

the working environment.

14C-VC was absorbed

inhalation chamber the

on activated charcoal.

These

After

traps were disposed of as

radio­

active waste according to standard regulations.

Procedure.

Eight rats were exposed

described previously.

On the

repeatedly to VC as

last day,

5 additional unexposed

rats and the 8 rats exposed repeatedly were exDosed to 5000
ppm
14

14

C-VC for 6 hours.

C-VC,

1ollowing

this

final exposure to

3 of the 8 exposed repeatedly and

once were placed in glass
collection of urine,

2 of

the

5 exposed

Roth-type metabolism cages

for

feces and expired air.

Room air was drawn through the cages at 400-500 ml/min.

*4C-VC and

through a series of
^COj.

The air

traps

leaving

The

to collect

the chamber

R &S 103910

exiting air was passed
the expired

the

-6-

was passed

firr.t

of Dricritc

(W.

through a glass
A.

tube I’ontaini m; about

Hammond Driorito Co.)

Subsequent transit through a series of
containing 50 ml of

toluene,

single trap containing

to

two cold

The cold

methoxyethanol,

dry

finger

ice baths

tion of exposure and analyzed

throughout

for

for

immersed

2C>2,

in

2-

the collection

at 12 hr

'ntervals

(immersed

for 72 hr;

At the termination of

in dry
and

activity.
(50% w/v)

liver)

3

hr;

ice bath)

the CO2 trap
were changed

feces were collected every

the study

were killed by a blow to the head,
kidney,

for

Expired

(72

hr)

the animals

and samples of

were collected

The remaining carcass was

tissues

for analysis of
skinned and homogenized

in distilled water and analyzed

for

The samples of excreta and tissue were prepared
lation counting as described previously

activity.
for scintil­

(Watunabe,

et al.,

R&S 103911

and urine receptacle

72 hr after termina­
activity.

VC was collected at 0.5 hr intervals

1976).

in

and a

14C-VC and

traps were

Samples of excreta were collected

(fat,

(80:20),

The trap for C02 was maintained at room temperature.

periods.

24 hr.

finger traps

5 M ethanolamine

mcthoxyethanol enabled the collection of
respectively.

remove moisture.

2-mcthoxyothnnol

120 ml of

40 g

-7-

Carbon

14 activity was determined by counting

or Mark

III

liquid scintillation spectrometer.

standard channels ratios were used
efficiency.

The remaining rats
singly to VC,

in

5 and

the countinq
to disinte­

standard quench curve.

3 rospectivley,

repeatedly and

were killed by a blow
A piece of

9000 x g super^atent in 1.15%

in order to determine aniline hydrolyxlase

1971)

and £-nitroanisole 0-demethylase

1966)

activity.

(LaDu,

(Kinoshita,

et al.,

et al. ,

Macromolecular binding of radioactivity to

hepatic tissue was determined by the method of Jollow,
(1974).

et al.

The carcass was analyzed for total radioactivity as

described above.

A second experiment was conducted to confirm parameters
obtained for binding of radioactivity to hepatic macromolecules.
The methodology was

the same as described above.

rats were repeatedly exposed

8 weeks.

to VC

(4821 ppm +

On the last day of exposure

additional 4

rats

were added.

analytical concentration of

the

*4C-VC on

exposure was

(SD)

and

34 dpm per microgram VC.

30

259,

SD)

for

^C-VC was used and an

(singly exposed group)

5005 ppm i

A group of

the

the

The mean

last day of

specific activity was

R&S 103912

following exposure.

liver was used to prepare a
KCl

to determine

the gre ’.ns exposed

immediately

II

F.xternal

The counts per minute were converted

grations per minute usiny a

to the head

in a Mark

R&S 103913

-8-

PKStU.TS
14

Excretion of

C-activity within 72 hours after a

' 4
repeated exposure to 5000 pom - C-VC
14

The percentage of
well as

the

groups.

shown

in Table

1.

C-activity excreted by. each route as

total mg equivalents VC

tially identical

is

single or

recovered were essen­

for the singly and repeatedly exposed

The majority of

14

C-activity eliminated was expiree

as VC per se.

The time course for expiration of 14C-VC per se

(Figure

and urinary excretion of

were also

^C-activity

(Figure 25

1)

essentially identical for the singly and repeatedly exposed
rats.

The curves were fit by linear regression analysis of

the logarithmically transformed data.
apparent first order
0.023 min ^
30 minutes.
biphasic.

±

0.01

rate constant for expiration of VC was

(SD)

which corresponds

The elimination of urinary
An estimate of the apparent

constant for the

to a half-life of

^C-activity was
first order rate

initial portion of the urinary excretion

curve from 12-36 hours was
corresponds

The estimate of the

0.155 hr”1

to a half-life of

±

0.02

4.47 hours.

(SD)

which

The data

for

the

slow phase of urinary excretion were extremely variable;
therefore no attempt was made

to estimate

rate.

the

Less

than 1 percent of

the excretion

radioactivity excreted in

the urine occurred during the slow phase.

-9-

Urinary

14

C-activity

graphy in n-butanol,
and n-butanol,

wig

separated by

acetone,

acetic acid,

t^O

The profile of radicactivity

thin

layer chromato­

(50:20:30) on cellulose
|W
(80:20:20) on silica gel.

for rats exposed repeatedly

or singly were qualitatively similar and no significant
radioactivity was associated with

the

value of a

standard of monochloroacetic acid.

i '.e concentration of radioactivity detected in tissue 72
hours after exposure revealed no statistically significant
difference between rats exposed once or repeatedly to
VC

(Table 2).

It does appear

that

in those exposed repeatedly

more radioactivity may have been retained in the
skin;

however,

liver and

the number of animals used does not provide

for an adequate statistical evaluation.

The effect of VC or xenobiotic drug metabolism by

liver 9000

x g supernatents as reflected by aniline hydroxylase and £nitroanisole-0-demethylase activity

is presented in Table 3.

Neither single or repeated exposure

to

discernibly

5000 ppm VC altered

the enzyme activity in either system when

compared to air exposed controls.

molecular binding of

^C-activity

the hepatic macro-

following single and repeated

R&S 103914

The total amount of VC biotransformed and

-10-

exposure arc shown in Table 4.

The

total amount of VC biotrans­

formed was not sign;fieantly different between

the two groups.

However the hepatic masromolccular binding in the
ment appeared to be

increased

first experi­

in the rats exposed repeatedly.

When the protein binding was corrected for the amount of VC

increase was

(S/A x 100}

found.

a statistically significant

Because the

increased binding in

repeatedly exposed rats was not definitive in the
experiment,

the experiment was repeated and

shown in the lower portion of Table 4.

first

the results are

The second study

confirmed tne observation that rats repeatedly exposed

to

VC bind about 20-25% more reactive metabolite to hepatic
macromolecules than rats exposed once.
the binding was

The magnitude of

slightly greater in the second experiment.

This was caused by a slightly higher concentration of ^C-VC
in the latter study

(5065)

ppm versus

the

former

These results indicate t.iat a larger fraction of

(4600 ppm).
the bio­

transformed VC reacts covalently with hepatic macromolecules
in rats exposed repeatedly.

R&S 103915

biotransformed

-11-

Discunsior;

Repeated exposure of rats

to

5000 ppm

14

C-VC did not alter

discernibly the routes or rates of excretion of radio­
activity or qualitatively
from VC or VC per se.

the excretory products

These results

negate

formed

the previous

preliminary observation that monochloroacetic may be a
major biotransformation product of VC

(Hefner,

e_t a_l. ,

1975).

A most significant finding in the study was a significantly
increased amount of radioactivity bound covalently to macro­
molecules cf
exposed once.

rats exposed repeatedly to VC versus

those

An associated observation was the retention

of an apparently greater level of radioactivity in the

exposed once.
tions,

72 hours after exposure than those

These results

indicate that toxic manifes a-

including carcinogenicity,

associated with the reaction

of reactive metabolites of VC with macromolecules may be
enhanced by repeated exposure to VC.

While the binding of reactive metabolites of VC to hepatic
macromolecules was enhanced following repeated exposure,

no

differences were observed in the activity of hepatic micro­
somal enzymes

to the substrates aniline or £-nitroanisole

in any of

treatment groups when compared to non-exposed

the

R&S 103916

of repeatedly exposed rats

liver

control

rats.

Thus,

it did

at this concentration
However,

in contrast

by Reynolds,

et a_l.

not appear

than exposure*

to VC

influenced microsomal metabolism.
to

those

(1975b)

findirgs was

that

the observation

the cytochrome P-450 content

and the oxidative N-demethy 1ntion of amino-antipyrme and
ethylmorphine were markedly depressed in rats
exposure

for 6

hours.

The difference between

that of P^ynolds,

e_t a_l.

(197 5b)

to 50,000 ppm VC

our study and

substrates which cause a

"type

used substrates producing a
hepatic microsomes.

II"

binding

"type I"

that we used

spectra and they

The apparent discrepancy can be explained
"type

spectra when incubated with hepatic microsomes
et al.,

is

binding spectra with

by the recent observation that VC causes a

Ivanetich,

following

1977).

Thus

I" binding

(Salmon,

it appears that VC

1976,

is metabo­

lized by the hepatic microsomal enzymes and is capable of
inhibiting metabolism of other substrates which interact with
cytochrome P-450 producing similar type

In conclusion,

the results of these

repeated exposure

I binding spectra.

studies

showed

that

to high levels of VC did not alter dis-

cernibly the routes or rates of excretion of radioactivity when
compared
ppm

14

to rats subjected to a single 6-hour exposure to 5000

C-VC.

Of particular significance was evidence

that

binding of reactive metabolites of VC with hepatic macro-

the

R&S 103917

-12-

-13-

moleculcs was enhanced by repeated exposure
VC.

Associated with

to hiuh levels of

this may be expected an enhanced

including carcinogenicity.

The

toxicitv,

reason for the enhanced

covalent binding with repeated exposure

is under

investigation.

ACKNOWLEDGEMENTS

their appreciation to M.

Schlachter ior technical assistance.

M.

R&S 103918

The authors wish to express

-14rki'erklci:;'-

Barbin, A., BrentL, H., Croisy, A., .u'.ci|uu;.K'n, !'.,
Ha 1 av i« 1 Lv ,
Mi -at.', a.mo , i . and Itirt.jii, H.
(1975).
Liver mcrusomt: nediaLvd 1‘urnacion rif
alkylating agents from vinyl oromido and vinyl
chloride.
Biochem. Biouhvs. Krs. Comm., b7,
596 603.
Bartsch, H., Malaviello, C., and Montesano, R. (1975).
Human rat, and mouse liver mediated mutaaenicity of
vinyl chloride in Sal mo null a tvn,,iir.ur ium strains.
Int. J. Cancer, 15, 429-437.
Bolt,

H. M. , Kappus, 11. , Buchter, A., and Bolt, W.
Metabolism cf vinyl chloride.
Lancet, 1425.

(1975).

Hefner, R. E. Jr., Watanabe, P. G., and Gehring, P. J.
(1975).
Preliminary studies of the fate of inhaled
vinyl choride monomer (VCM) in rats,
Ann. N.Y.
Acad. Sci., 246, 135-148.

Jollow, D, J., Thorgeirsson, S. S., Potter, W. Z.,
Hashimoto, M. and Mitchell, J. R. (1974).
Acet­
aminophen-induced hepatic necrosis VI., Pharmacology, 12, 251-271.
Kappus, H., Bolt, H. M., Buchter, A. and Bolt, W. (1975).
Rat liver microsomes catalyze covalent binding of
14C-vinyl chlorice to macromolecules, Nature, 257,
134-135.
-------------Kinoshita, F. K., Frawley, J. P. and DuBois, K. P. (1966).
Quantitative measurement of 'nduction of hepatic
microsomal enzymes by various dietary levels of DDT
and toxaphene in rats.
Toxicol. Appi. Pharmacol.,
9, 505-513.
-------------------------------LaDu,

B. N., Handel, H. G. and Way, E. L. (ed.) (1971).
Fundamentals of Drug Metabolism and Drug Disposition,
PP* 566-569, Die Williams and Wilkins Co., Baltimore,
Maryland.

Malavielle, C., Bartsch, H., Barbin, A., Camus, A. M. and
Montesano, R. (1975).
Mutagenicity of vinyl chloride,
chi oroethy 1 oru-cx icic , ch loroacvta ldohydo .md chloroethar.ol ,
Mioclum, Biophy;;. Rim. Comm., 63, 363-370 .

R&S 103919

Ivanetich, K. M., Aronson, I. and Katz, I. D. (1977).
The
interaction of vinyl chloride with rat hepatic micro­
somal cytochrome P-4 50 in, vitro.
Biochen. Biophvs.
Res. Comm., 7£, 1411-1418.

-15-

Rannug, U., Johansson, A., Hamel, C. and Washcmcister,
C. A. (197*1).
The mutaucnicitv of viiy 1 chloride after
metabolic activition, Air.bio, j., 194-J.97.
Reynolds, E. S., Moslen, M. T., Szabo, S., Jaeger, R. J.,
and Murphy, S. D. (1975a).
Hepatotoxicity of vinyl
chloride and 1,1-dichloroethylenc.
Am. J. Path., 81
(1), 219-231.
Reynolds, E. S., Maslen, M. T., Szabo, S. and Jaeger, R. J.
(1975b).
Vinyl chloride induced deactivation of cyto­
chrome P-45u and other components of the liver mixed
function oxidase system:
on ill vivo study.
Res.
Comm. Chem. Patn. Pharmacol,, 1_2(4), 685-693.
Salmon, A. G. (1976).
Cytochrome P-450 and the metabolism
of vinyl chloride.
Cancer Letters, 2, 109-117.
(1975) .
A procedure for
chloride.
Ann. N.Y.

Wagner, E. R., Muelder, W. W., Watanabe, P. G., Hefner,
R. E., Jr., Braun, W. H., and Gehring, P. J. (1975).
Gas chromatographic method for the preparation of
14C-labeled vinyl chloride, J. Labeled CcmDounds, 11,
535-542.
‘
Watanabe, P. G., McGowan, G. R., Madrid, E. 0. and Gehring,
P. J. (1976).
Fate of 14C-vinyl chloride following
inhalation exposure in rats.
Toxicol. Appl. Pharmacol.,
37, 49-59.
--------------------------------

R&S 103920

Wagner, E. R. and Muelder, W. W.
preparina ll*C-labeled vinyl
Acad. Sci., 246, 152-153.

R&S 103921

-16-

TABLE
Percentage

1

^C-Activity Eliminated During

Following Inhalation Exposure

to

Single Exposure(2)b
___JL(mg onuiv.

VC)

5000

72

Hours

ppm ^C-Vinvl Chloride13

Repeated E xposure( 3)b
%(nq
eguiv. VC)

Expired:
as VC

54.5+3.5

(14.0)

53.7+2.1

112.94)

as CC>2

8.0+1.4

(2.05)

9.011.6

(

2.27)

Urine

27.1+2.1

(6.93)

25.7+1.4

(

6.21)

Feces

3.2+2.5

(0.80)

1.4+0.4

(

0.32)

Carcass and

7.312.5

(1.89)

9.7 + 1.6

(

2.32)

TissJes

Total mg equivalents
VC recovered

(25.67)

(24.07)

Expressed as percentage of the total
C-activitv recovered, mean ±
^Number of rats.

SD

-17Table

Percentage

14

C-Activity per Gram Tissue 72 Hour Following

Inhalation Exposure

to 5000 ppm Vinyl Chloridea

„
14
Percentage
.C-Activi ty-'a Tissue
Single Exposure(i)
Repeated Exposure

Liver

0.1191.0.022

0.157+0.028

Kidney

0.062+0.026

0.070+0.006

Fat

N.D.C

N.D.C

Skin

0.046+0.015

0.080+0.019

Carcass

0.030±0.014

0.039+0.011

Expressed as percentage of the total 14C-activity metabolized,
mean + SD.
^Number of rats/group.
Q
Not detectable, detection limit of 3 ug VC equiv./g fat cr
0.03 percent 1'"C-activity metabolized per g tissue.

■b

R&S 103922

Tissue

2

-18-

Tab lc

j

Effect of Vinyl Chloride on Drug Metabolism Bv
A 9,000 x g Supernatent Fraction of Livera

Control

(4)b

Single VC
Exposure

.

liver/hour
p-Nitroanisole
O-Dcmethylase

65±16

226+22

71+7

254+45

83+10

217+31

(3)

Repeated VC
.
Exposure (5)°

Animals were killed immediately following the last exposure
and enzyme activity assayed.
Values are means + SD.
^Number of rats/group.

R&S 103923

ng nroduct/g
Aniline
—
Hydroxylase

Table 4

Total Metabolism and Hepatic Macromolecular Binding Following
Single or Repeated Exposure to 5000 ppm Vinyl Chloride3

A

B

lig VC Equivalents
Metabolized

yg VC Equivalents
Bound per g Protein

Binding Corrected
For Metabolism,
____B/A x 100b

Single Exposure

9265*1467

114+10

1.12+0.13

Repeated Exposure

8718*895

124i10

1.43 + 0.16°

<D
I
EXPERIMENT WAS REPEATED
Single Exposure

8746+882

148+25

1.69+0.28

Repeated Exposure

9421+482

195+24°

2.07+0.25°

aValues are means + SD

(3-5 rats/group).

'The ratio of B/A x 100 was calculated
c

*rom the individual animal data,

Statistically significant from the single exposure. Student t-test

PZ6£0l S9U

(p < 0.05).

B&S 103925

-20-

LEGENDS

Figure 1

Expired vinyl chloride

(mg)

following a 6 hour exposure
14

C-VC.

time

to 5000 ppm

Repeatedly exposed animals

and singly exposed animals

Figure 2

versus

(x)

(•).

C-activity excreted in the urine expressed
as percentage of the recovered radioactivity
versus time following a 6 hour exposure to
5000 ppm ^C-VC.
(x)

Repeatedly exposed animals

and singly exposed animals

(•).

R&S 103926

mg VC Expired

FIGURE 1

Percent of Recovered 14C-Activity

FIGURE 2

FIGURE 2

100

80
60
40
30

Percent of Recovered ,4 C-Activity

20

10
8
6

4
3
2

1

0.8
0.6

2

0.4
0.3
0.2

i

12

24

36

48

T'me (Hours)

i

72

84

R&S 103927

_!______L

0.1