TOXICOLOGY

AND

APPLIED

PHARMACOLOGY

45.809-g

19 (1978)

Changes in Serum Enzymes in Rats After Inhalation Organic Solvents Singly and in Combination ROBERT T. DREW,’ J. M. PATEL,~ National

Institute

of Environmental

Received

October

AND FAN-NAN

Health Science, P.O. Box 12233, North Carolina 27709 12, 1977; accepted

February

of

LIN

Research

Triangle

Park,

17.1978

Changes in Serum Enzymes in Rats After Inhalation of Organic Solvents Singly and in Combination. DREW, R. T., PATEL, J. M., AND LIN, F. (1978). Toxicol. Appl. Pharmacol. 45. 809-819. Using death as an endpoint, it has been demonstrated that tetrachloroethylene (TCE) produces a greater-than-additive effect when given orally in combination with several other compounds. We have attempted to determine more sensitive indicators which would respond in a synergistic fashion when animals are exposed by inhalation to combinations of organic solvents. Male rats were exposed for 4 hr to various concentrations of TCE, dioxane, butyl ether (BE), acetonitrile (ACN), trichloropropane (TCP), and dichloropropane (DCP). The serum enzymes, glutamic oxalacetic transaminase (SGOT), glutamic pyruvic transaminase (SGPT). glucose-6-phosphatase (G-6-Pase), and ornithine carbamyl transferase (OCT) were measured in rats prior to exposure, immediately after exposure, and at 24 and 48 hr after exposure. The enzymes, SGOT, SGPT and OCT. were markedly elevated as a result of exposure to the above compounds, whereas G-6-Pase was only occasionally altered. Neither TCE in combination with dioxane, BE, or ACN nor TCP with DCP resulted in a greater-than-additive effect. On the contrary, in many instances the effects were significantly less-than-additive when tested for interaction.

Reports of studies on the toxicity of combinations of compounds are scarce in the literature. Recently, studies have been published in which investigators studied the effects of atmospheric oxidants when exposed together (Goldstein, 1976; Sidorenko et al., 1976; Hackney et al., 1975; Alarie et al., 1975). Sulfur dioxide has been shown to increase the incidence of lung tumors resulting from exposure to benzolalpyrene (Laskin et al., 1970). Earlier, researchers at the Mellon Institute reported on the relationship between LC50 values of individual vapors and composite vapors (Pozzani et al., 1959). Over a series of years this group studied the toxicity of a variety of chemicals and in 1969 reported on the joint peroral toxicity of 350 pairs of 27 industrial chemicals (Smyth et al., 1969). They compared the measuredvalue for the LC50 for a pair of chemicals to that predicted by Finney’s model for additive joint toxicity (Finney, 1952). Mathematical and intuitive treatment of the data indicated that those pairs where the ratio of measuredto calculated LD50 differed greatly from one may be reacting in other than random fashion. Inspection showed that tetrachloroethylene (TCE) and ’ Present address: Medical Department, Brookhaven National Laboratory, York 11973. ? Present address: Department of Pharmacology and Therapeutics, J. Miller Florida Medical School. Gainesville. Florida 32608. 809

Upton, Helath

Long Center.

Island. University

New of

0041-008X/78/0453-0809%02.00/0 CopyrIght (Q 1978 by Academic Press. Inc. All righlr of reproduction in any form reserved. Printed in Great Elritairl

DREW,

810

PATEL,

AND

LIN

carbon tetrachloride react in a greater-than-additive fashion with several different compounds. Withey and Hall (1975), taking note of Smyth’s work, also exposed rats per OS to various mixtures of TCE and either benzene or toluene. They determined that TCE and benzene gave values for the LD50 which were slightly less-than-additive, while mixtures of toluene and TCE had LD50 values which could not be predicted by an additive model. The endpoint in the above studies was death. The object of the studies reported here was to develop more sensitive indices of synergism, hopefully indices which could be measured in humans. Since human sera are readily available and since serum enzyme concentrations have been reported to change following exposure of animals to organic solvents (Carlson, 1974) the emphasis of this study was on serum enzymes. Serum glutamic oxalacetic transaminase (SGOT), serum glutamic pyruvic transaminase (SGPT), glucose-6-phosphatase (G-6-Pase), and ornithine carbamyl transferase (OCT) were studied. When TCE was given in combination with acetophenone, dioxane, butyl ether, polyethylene glycol, morphoiine, or acetonitrile, the toxicity of the pair was more than twice that predicted by Finney’s model (Smyth et al., 1969). Thus, we attempted to TABLE GLUTAMIC

OXALACETIC

TRANSAMINASE ACTIVITY IN RATS AFTER SOLVENTS SINGLY AND IN COMBINATION

TCE (2000 ppm)b TCE (1000 ppm) TCE (500 ppm) Dioxane (2000 ppm) Dioxane (1000 ppm) TCE (900 ppm) and Dioxane ( 1200 ppm) BE (2000 ppm) TCE (1000 ppm) and BE (2000 ppm) 1 ACN (3000 ppm) TCE (1000 ppm) and ACN (3000 ppm) TCP (500 ppm) DCP (1000 ppm) TCP (500 ppm) and DCP (1000 ppm)

EXPOSURE

TO SELECTED

Day 0

Day 1

Day 2

24.7 2 0.70

24.4 + 0.4

25.5 + 0.5

25.2 + 0.5

25.4 21.8 26.2 25.1 26.0

49.4 31.4 28.2 27.6 26.8

Day

Control

1

-1

+ 2 + k f

1.2 1.5 0.9 1.1 0.8

& * k k f

1.9c 1.2c 0.9’ l.lc l.l=’

105.6 51.1 34.2 49.8 33.1

t 6.5c k 2.0’ k 0.5' 5 l.lc t_ 0.T

141.1 63.8 27.1 54.4 33.9

_+ 4.T rf: 1.8' k 0.8 + 2.0c f l.lC

24.6 k 0.1

24.9 + 0.8

45.6 2 2.1'

46.0 & 1.4c

25.3 k 0.7

23.9 + 0.7

39.6 k l.lc

34.3 + 0.8'

25.3 f 0.6

23.4 f 0.5

66.6 +_ 1.8c

65.8 +_ 1.8'

26.4 & 0.3

26.3 f 0.5d

62.1 f l.gc

70.2 * 1.3c

25.7 2 0.4

27.2 + 0.5’

65.5 + 1.5c

81.0 + 2.2c

24.6 + 0.6 25.1 k 0.8

26.1 k O.Td 27.3 5 I.ld

41.7 + 1.9’ 41.4 k l.OC

44.4 + 1.7c 60.6 + 1.8c

23.4 k 0.6

26.2 f 0.9

60.5 + 2.1c

64.9 f. l.gc

u The data are expressed as means + SE. b Abbreviations used: TCE, tetrachloroethylene; BE, n-butyl ether; ACN; acetonW.-. TCP. trichloropropane; and DCP, dichloropropane. =Different than controls,g < 0.01. d Different than controls, p < 0.05.

SOLVENT ELEVATION

811

OF SERUM ENZYMES

expose rats to the combinations listed above. Technical difficulties were encountered in the generation of morpholine, polyethylene glycol, and acetophenone. Therefore, studies reported here include separate exposures to various concentrations of TCE, dioxane, butyl ether (BE), and acetonitrile (ACN) and combinations of TCE with the other three. In addition, since these studies were carried out as part of the U.S.-U.S.S.R. Scientific Information Exchange Program, we also studied 1,2-dichloropropane (DCP) and 1,2,3trichloropropane (TCP), two compounds of interest to our Soviet colleagues. For all the combination studies, the concentrations of each compound that raised the enzyme activity by a factor of 2 or 3 were selected so as not to exceed the maximum response. METHODS

Male CD 1 rats weighing 200 to 250 g were used in this study. Spectrograde test compounds were purchased from conventional sources and were assayed for purity by gas chromatographic analysis. In all cases compounds greater than 99% pure were used. Vapors were generated by passing air through a bubbler containing the test compound into a dilution airstream and then into an inhalation chamber. The stainless TABLE GLUTAMIC

2

PYRUVIC TRANSAMINASE ACTIVITY IN RATS AFTER EXPOSURE TO SELECTED SOLVENTSSINGLYANDINCOMBINATION

Day Control TCE (2000 ppm)b TCE (1000 ppm) TCE (500 ppm) Dioxane (2000 ppm) Dioxane (1000 ppm) TCE (900 ppm) and Dioxane ( 1200 ppm) BE (2000 ppm) TCE (1000 ppm) and BE (2000 ppm) 1 ACN (3000 ppm) TCE (1000 ppm) and ACN (3000 ppm) TCP (500 ppm) DCP (1000 ppm) TCP (500 ppm) and DCP (1000 ppm)

Day 0

Day

28.8 & 0.7“

29.1 5 0.6

29.2 + 0.4

32.2 32.8 33.2 32.6 32.6

41.9 31.0 34.2 35.0 31.7

+ f k + k

-1

1.8 0.9' 0.8c 0.9c 0.8'

* l.lC f k + *

0.6c 0.6c l.5c 1.2

65.7 46.2 33.6 51.7 35.0

+ k t f

1

2.4c 2.4c 0.4c 1.5c

* 1.0’

Day

2

29.3 + 0.5 141.1 49.8 32.8 52.8 34.4

+ 6.4O _+ l.6c & 0.6c + l.4c * 0.5c

31.4 2 0.7d

29.4 k 1.0

44.3 & 1.4'

44.0 + 1.3'

30.2 + 0.8

28.6 k 0.6

50.4 + 1.6'

46.5 k l.oC

31.5 f 0.4'

29.9 + 0.2

59.4 5 1.9'

59.5 + 0.6c

30.2 + 0.5

30.2 k 0.5

62.1 k 1.7'

72.5 i- l.6c

30.2 k 0.6

31.7 + 0.6d

81.9 + 2.2c

91.0 k 2.4c

30.1 k 0.8 31.2 + 0.8

32.1 + l.od 31.1 * 1.7

54.4 & 2.w 44.0 k 1.7c

54.9 + 1.5c 66.5 & 2.2c

28.9 + 1.0

31.2 k 1.6

74.1 * 3.3'

69.1 & 2.6c

0 The data are expressed as the mean f SE. ’ Abbreviations used: TCE, tetrachloroethylene; propane; and DCP, dichloropropane. c Different than controls, p < 0.0 1. d Different than controls, p < 0.05.

BE, n-butyl

ether:

ACN;

acetonitrile;

TCP,

trichloro-

812

DREW,

PATEL,

AND

LIN

steel-Lucite chambers were 128 L and of the type described by Laskin et al. (1970). Concentrations were continuously monitored by an automatic gas sampling Varian 1400 gas chromatograph using a flame ionization detector or a Miran II infrared analyzer. Blood for the serum enzyme assay was drawn via heart puncture 24 hr prior to exposure (Day -l), within 1 hr after a single 4-hr exposure (Day 0), 24 hr after exposure (Day l), and 48 hr after exposure (Day 2). In this way each rat served as his own control. Each experiment started with 15 animals; however, consecutive daily heart punctures caused several deaths. Occasionally, a blood sample could not be obtained, was too small, or was lost. The data reported here are the average of all the samples available at the time point in question. The method of Karmen (1955) was used to measure SGOT and SGPT, and the results are reported in Karmen units per milliliter. Serum G-6-Pase and OCT were estimated by the methods of Koide and Oda (1959) and Reichard and Reichard (1958) respectively, using a Zeiss M.H.Q. III recording spectrophotometer. Glucose-6phosphatase is reported in micrograms of inorganic phosphorus per milliliter @g of Pi/ml). Ornithine carbamyl transferase is reported in Sigma units/ml. Analysis of variance procedures (Snedecor and Cochran, 1967) were used to assess the overall significance of treatment effects and interactions. The interactions were TABLE

ACTIVITY IN RATS AFTER EXPOSURE SINGLY AND IN COMBINATION

GLUCOSE-6-PHOSPHATASE

Day -1 Control

TCE (2000 ppm)b TCE (1000 ppm) TCE (500 ppm) Dioxane (2000 ppm) (1000 ppm) TCE (900 ppm) and Dioxane (1200 ppm) BE (2000 ppm) TCE (1000 ppm) and Dioxane

BE (2000 ppm) ACN (3000 ppm) TCE (1000 ppm) and ACN (3000 ppm) TCP (500 ppm) DCP (1000 ppm) TCP (500 ppm) and DCP (1000 ppm)

3

1

TO SELECTED

Day 0

Day

1

SOLVENTS

Day 2

3.95 + 0.02”

3.96 _+ 0.02

3.91 It 0.02

3.98 + 0.02

4.51 4.28 4.07 3.94 4.07

4.75 4.33 4.16 3.79 3.86

5.11 5.21 4.34 3.98 4.09

6.05 4.29 4.05 4.06 4.07

* 0.07r 4 0.07c * 0.05 k 0.03 +_ 0.06

+ 0.15c + 0.06c 5 0.06c f 0.05’ +_ 0.04

k 0.15’ k 0.04c k 0.03’ & 0.03 * 0.05

k 0.16c + 0.05c f- 0.03d + 0.03d +_ 0.05

4.11 2 0.04c

3.67 + 0.06c

3.96 + 0.03

3.99 & 0.03

4.02 + 0.08

3.88 + 0.08

4.04 k 0.06

4.13 * 0.07d

4.02 + 0.05

4.02 + 0.03

4.51 k O.lOC

4.19 i 0.04’

4.02 _+ 0.05

4.12 _+ 0.05’

4.96 _+ 0.09c

4.30 + 0.06c

4.09 f 0.06d

3.97 * 0.05

4.18 k- 0.04c

4.08 + 0.03d

3.82 2 0.03c 3.93 + 0.03

3.83 + 0.03c 3.85 + o.03c

4.01 + 0.02 4.02 & 0.02

3.93 + 0.02 3.91 +_ 0.06

3.93 t 0.03

3.44 + 0.04c

3.65 f 0.05c

3.94 & 0.04

” The data are expressed as means +_ SE. * Abbreviations used: TCE, tetrachloroethylene: propane; and DCP, dichloropropane. c Different than controls, p < 0.01. d Different than controls, p < 0.05.

BE. n-butyl

ether:

ACN,

acetonitrile:

TCP.

trichloro-

SOLVENT ELEVATION

813

OF SERUM ENZYMES

analyzed to compare the effects of the combined exposure to the sum of the effects expected when exposed to each of the compounds separately. Thus, the results can be significantly less-than-additive (antagonistic), additive (nonsignificant), or significantly greater-than-additive (synergistic). If significant among-group differences were detected, pairwise treatment vs control comparisons were made by Mann-Whitney U tests (Hollander and Wolfe, 1973). Each animal was also compared to its own Day -1 value by a Wilcoxon signed rank test (Hollander and Wolfe, 1973). These two procedures [comparing treated animals with (1) a separate control group and (2) their own pretreated values] generally yielded similar results.

RESULTS

Prior to testing any compounds, a series of controls was bled, sham-exposed and bled according to the protocol. These results are listed in the Tables and also plotted in Figs. 2 and 3. In one case, G-6-Pase on Day 2, the enzyme did differ significantly from the preexposure value @ < 0.05), but for 12 comparisons (four variables for 3 days) this is about what one would expect to find by chance alone. The actual numbers are in fact TABLE

4

ORNITHINE CARBAMYL TRANSFERASE ACTIVITY IN RATS AFTER EXPOSURE TO SELECTED SOLVENTS SINGLY AND IN COMBINATION Day -1 Control TCE (2000 ppm)b TCE (1000 ppm) TCE (500 ppm) Dioxane (2000 ppm) Dioxane (1000 ppm) TCE (900 ppm) and Dioxane (1200 ppm) I BE (2000 ppm) TCE (1000 ppm) and BE (2000 ppm) 1 ACN (3000 ppm) TCE (1000 ppm) and ACN (3000 ppm) I TCP (500 ppm) DCP (1000 ppm) TCP (500 ppm) and DCP (1000 ppm)

Day 0

213 + lO= 199 195 205 223 188

+ 9 & 11 + 13 +_ 10 * 10

217 + 7 566 401* 209 287 237

* 14c 13c + 14 f. 19< + 13

Day 1 214k8 1506 1199 461 574 453

+ + & + *

Day 2 222 _+ 10

46’ 54’ 16’ 19c 15c

1889 1262 229 602 440

+ 89’ & 38’ _+ 9 + lgc & 15’

231 f 10

298 + lc

906 +_ 36’

1079 +_ 22’

218 _+ 7

241 k 8d

229 + 6

219 + 7

392 k 12’ 882 + 35’

361 & 9’ 898 + 30c

247 + 5d

292 f 4’

781 + 31

903 1 25’

223 + 7

287 2 8’

700 & 32c

829 + 31c

239 f 8 194 + 8

263 + 8c 268 5 16d

492 + 14’ 663 k 11’

211*

309 * 9’

394 + lot 544 + 17’ 723 + 26’

10

772+21c

a The data are expressed as means + SE. b Abbreviations used: TCE, tetrachloroethylene; BE, n-butyl ether: ACN: acetonitrile: TCP, trichloropropane; and DCP, dichloropropane. c Different than controls,p < 0.01. d Different than controls, p < 0.05.

814

DREW,

PATEL,

AND

LIN

very close (3.95 vs 3.98) and the biological significance of this difference is minimal. Hence, the heart puncture procedure did not affect the results. The results are summarized in Tables 1 to 4 for SGOT, SGPT, G-6-Pase, and OCT, respectively for all of the various exposure conditions studied. The data for three different concentrations of TCE, two different concentrations of dioxane, and the combination of TCE and dioxane are shown in Fig. 1. At 2000 ppm, TCE markedly TETRACH-WTHYLEN

DIOXANE

DIOXANE (120O1+ TETRACHLOROETHYLENEB

i:,jj;;;/*z ~~~~~ L DAYS

.I 0 I 2 DAYS

-I 0 I 2 DAYS

FIG. 1. The effects of tetrachloroethylene (TCE), dioxane, and a mixture of the two on serum enzymes in the rat.

effects all four enzymes studied. This effect is present to a lesser extent at 1000 ppm and marginally present at 500 ppm. Dioxane at 2000 ppm also increases the enzyme concentrations, except for G-6-Pase. Only SGOT and OCT are markedly increased by a single 4-hr exposure to 1000 ppm of dioxane while SGPT is slightly increased 24 and 48 hr after exposure. For the combination exposure, nominal concentrations of 1000 ppm of both TCE and dioxane were selected. The actual average concentrations were 1200 ppm for dioxane and 900 ppm for TCE. For statistical analysis, the data were analyzed, assuming the nominal concentrations were attained. In addition, the sum of the enzyme concentrations estimated directly by linear extrapolation using the

SOLVENT ELEVATION

OF SERUM ENZYMES

815

individual compound data was calculated. The significance of the interaction was retested, based on these estimated values. Essentially the same results were found as those obtained from the analysis of variance procedures. A summary of the significant interactions for all the pairs is shown in Table 5. Since in some cases there were highly significant preexposure (Day -1) differences, the data were tested based on the difference from the preexposure values. The expected response in the combination group was calculated by adding the values obtained after exposure to the individual compounds and then subtracting the control value. This quantity was TABLE

5

SUMMARY OF INTERACTIONS OF ORGANIC SOLVENTS ADMINISTERED DIFFERENCE FROM PREEXPOSED VALUE~*~

Combination

SGOT

SGPT

1 2

; v

-

-u”

0

V -

V -

V -

Day 0

TCE’ + dioxane

TCE i- BE

1 2 0

TCE + ACN

TCP + DCP

TO RATS BASED ON

1 2

1

-

1

V u

-

-

-7

V

V

G-6-PASE

-uu

OCT

1: u

V

RThe expected value of the combination is the sum of the values obtained by exposure to the compounds singly minus the control value. b Definition of symbols: 1, observed value significantly lower than expected value @ < 0.05); #, observed value significantly lower than expected value @ 5 0.01); -, observed value not significantly different from expected value; and fi, observed value significantly higher than expected value (p I 0.01). c The abbreviations used are the same as those used in Tables 1 to 4.

compared to that observed after exposing the animals to the combination. After exposure to both TCE and dioxane there is a statistically significant less-than-additive effect for each of the enzymes immediately, and for all the enzymes but SGPT 24 hr after the exposure. After 48 hr the activity of SGOT and OCT were still lower than that expected if the effects were additive. Butyl ether, at 2000 ppm also causes elevated activity of SGOT, SGPT, and OCT both 24 and 48 hr after exposure. The nominal concentrations of 1000 ppm of TCE and 2000 ppm of BE were chosen for the combination exposure. The average values for the 4-hr exposure were 1040 and 1980 ppm, respectively. Unlike dioxane and TCE, BE and TCE when given together cause SGGT and SGPT concentrations at 24 and 48 hr to rise above those values obtained when each are inhaled singly (Fig. 2). However, the value for SGPT activity obtained at 48 hr is not as high as that expected (Table 5). The combination of TCE and BE causes lower G-6-Pase and OCT concentrations than a

DREW, PATEL,

816

AND LIN

similar concentration of TCE alone (Fig. 2). The combination produces a significantly less-than-additive effect for OCT at every time period investigated. Acetonitrile by itself also causes an increase in most of the enzymes measured. For the combination exposure the actual concentrations measured were 1075 ppm of TCE and 3030 ppm of TETRACHLOROETHYLENE

AND

BUTYL

DAYS

ETHER

DAYS TCE (1000)

2 \EICGO 2 5.C 600

TCEtBE

.5 L

L 0 200 -I

0

I

2

DAYS

FIG. 2. The effects of tetrachloroethylene (TCE), butyl ether (BE), and a mixture of the two on serum enzymes in the rat. TETRACHLOROETHYLENE

=I Cl00 L.3 c 5

60

6 $

20 -I

0

I

AND

ACETONITRILE

2

-I F

0

I 2 kTCE

2 1000 > 0L 5 -I

0 I DAYS

2

200 600

(1000) ABOOO) A+TCE

CONTROL k

-I

0 I DAYS

2

FIG. 3. The effects of tetrachloroethylene (TCE) and acetonitrile (ACN) and a mixture of the two on serum enzymes in the rat.

ACN vs target concentrations of 1000 and 3000 ppm, respectively. The results for TCE and ACN are qualitatively similar to the combination of TCE and BE (Fig. 3). However, SGOT responds in a significantly less-than-additive fashion 24 and 48 hr after the exposure, as do G-6-Pase and OCT at all times studied (Table 5). Finally, Fig. 4 shows a plot of the data for 1000 ppm of DCP and 500 ppm of TCP singly and in combination. The measured values were within 1% of the target values. Glucose-6-phosphatase is not changed by these compounds separately at these

SOLVENT

ELEVATION

OF

SERUM

817

ENZYMES

concentrations, although together they cause an initial depression. SGOT, SGPT, and OCT all are increased by both compounds. This effect at 24 hr is additive for SGOT and OCT. The only greater-than-additive result observed in the study was for SGPT, at 24 hr. By 48 hr, the combination does not produce an additive effect and in fact is significantly less-than-additive for SGOT, SGPT, and OCT (Table 5). DlCHLO.ROPROPANE

?I00 z-2 2 60 L ::

COMBINATION 1000 PPM DCP TCP

20 -I 0 I DAYS

2

8 TRICHLOROPROPANE

z 100 ; 80 Y 60 f

40

g 07

20

COMBINATION 1000 PPM DCP 500 PPM TCP

.I 0 I 2 DAYS 900

2700

COMBINATION 1000 PPM DCP

\ 2 32 500

500

PPM TCP

: 300 cl 100 -I

FIG. 4. The effects of dichloropropane serum enzymes in the rat.

0 I 2 DAYS

(DCP) and trichloropropane

(TCP) and a mixture of the two on

DISCUSSION

The transaminases have been shown to increase in sera as a result of exposure to many organic solvents (Todd-Sanford, 1969). SGOT is fairly nonspecific, being elevated in patients with cardiac disease and hepatic disease as well as with other specific conditions. SGPT is more specific, usually indicating only hepatobiliary disease. OCT is even more specific, being an index of acute hepatic injury. The results obtained thus indicate that the hepatocytes are injured, since qualitatively all three enzymes appear to parallel one another, and since the most dramatic increases are in OCT. G-6Pase has been shown to increase in preparations of liver homogenates after hepatic injury (Finney, 1952), and thus we attempted to measure it in serum. For the most part this enzyme is not nearly as susceptible to exposure to the solvents studied. The chemical structures of the three compounds tested with TCE are all markedly different. However, each, when exposed with TCE, gives a signi8cantly less-thanadditive or protective effect as measured by a decreased OCT response at all time points with each compound. The SGOT and SGPT results are somewhat ambiguous, about half the responses being significantly less-than-additive and about half the responses being additive. The original hypothesis, namely, that these enzymes might respond in a synergistic fashion was proven incorrect. The chemical structures of TCP and DCP are similar, and thus one would expect these enzymes to act in an additive fashion. With the exception of G-6-Pase, the enzyme

818

DREW, PATEL, AND LIN

activities were higher during the combined exposure than they were during exposure to the individual compounds. However, the increase was often not enough to describe the interaction as additive (Table 5). The single significant greater-than-additive effect observed for SGPT on Day 1 may not be too important since it is less-than-additive by the next day. These results suggest that these serum enzymes may not be good indicators of toxicity of combined exposures. Since each of the compounds tested with TCE often gives a less-than-additive response, the deaths resulting from combined exposure to these pairs are probably not due to liver damage. ACKNOWLEDGMENTS

The authors would like to thank Dr. Hans Falk, Dr. James McKinney, and Dr. E. W. van Stee for their suggestions and discussions about this project. The contributions of Mr. Willie Gibson in setting up methods of generation and characterization of the compounds are appreciated. Finally, we would like to thank Mr. M. T. Riley and Mr. F. Harrington for their assistance in carrying out the exposures. REFERENCES ALARIE, Y. C., KRUMM, A. A., BUSEY, W. M., ULRICH, C. E., AND KANT& R. J., II (1975) Long term exposure to sulfur dioxide, sulfuric acid mist, fly ash, and their mixtures. Arch. Environ. Health 30,254-262. CARLSON, G. P. (1974). Enhancementof the hepatotoxicity of trichloroethyleneby inducersof drug metabolism.Res.Commun.Chem.Pathol. Pharmacol.7,637-640. FINNEY, D. J. (1952).In Probit Analysis, 2nd ed., p. 131. CambridgeUniv. Press,London/New York. GOLDSTEIN, B. D. (1976). Combinedexposureto ozone and nitrogendioxide.Environ. Health Perspect.13, 107-l 10. HACKNEY, J. D., LINN, W. S., BUCKLEY, R. D., PEDERSEN, E. E., KARUZA, S. K., LAW, D. C., AND FISCHER, D. A. (1975).Experimentalstudieson humanhealtheffectsof air pollutants,I, II, III. Arch. Environ. Health 30,373-390. HOLLANDER, M., AND WOLFE, D. A. (1973). NonparametricStatistical Methods. Wiley, New York. KARMEN, A. (1955). A note on the spectrophotometricassay of glutamic oxalacetic transaminase in humanblood serum.J. Clin. Invest. 34, 13l-135. KOIDE, H., AND OT)A, T. (1959). Pathologicaloccurrenceof glucose-6-phosphatase in liver disease.Clin. Chim.Acta 4, 554-561. LASKIN, S., KUSCHNER, M., AND DREW, R. T. (1970).Studiesin pulmonary carcinogenesis. In Inhalation Carcinogenesis Conference691001 (M. G. Hanna, Jr., P. Nettesheim, and J. R. Gilbert, eds.), Clearinghousefor Federal Scientific and Technical Information, NBS, U.S. Dept. Commerce,Springfield,Va. POZZANI, U. C., WEIL, C. S., AND CARPENTER, C.P. (1959).The toxicologicalbasisof threshold limit values: 5. The experimentalinhalationof vapor mixturesby rats, with notesupon the relationshipbetweensingledoseinhalationand singledoseoral data.Amer. Znd.Hyg. Assoc. J. 20, 364-369. REICHARD, H., AND REICHARD, P. (1958).Determinationof ornithine carbamyltransferasein serum.J. Lab. Clin. Med. 52, 709-7 11. SIDORENKO, G. I. (1976). Methodological approachesto the study of the combinedeffect of atmosphericpollutantsasillustratedby chlorinatedhydrocarbons.Environ. Health Perspect. 13,111-116.

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ELEVATION

OF SERUM

ENZYMES

819

H. F., JR., WEIL, C. S., WEST, J. S., AND CARPENTER, C. P. (1969). An exploration of joint toxic action: Twenty-seven industrial chemicals intubated in rats in all possible pairs.

SMYTH,

Toxicol. Appl. Pharmacol.

G. W., Ames,Iowa.

SNEDECOR,

14,340-341.

AND COCHRAN,

W.

G. (1967). Statistical

Methods.

Iowa State Univ. Press,

(1969). In Clinical Diagnosis (I. Davidsohnand J. B. Henry, eds.), 15th ed. Sanders,Philadelphia,Pa. WITHEY, R. J., AND HALL, J. W. (1975). The joint toxic action of perchloroethylenewith benzeneor toluenein rats. Toxicology 4,5-15. TODD-SANFORD.

Changes in serum enzymes in rats after inhalation of organic solvents singly and in combination.

TOXICOLOGY AND APPLIED PHARMACOLOGY 45.809-g 19 (1978) Changes in Serum Enzymes in Rats After Inhalation Organic Solvents Singly and in Combinat...
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