Fd Chem. Toxic. Vol. 24, No. 6/7, pp. 653-654, 1986 0278-6915/86 $3.00+0.00 Printed in Great Britain. All rights reserved Copyright © 1986 Pergamon Journals Ltd

TRIFLUOROETHANOL A N D ITS OXIDATIVE METABOLITES: COMPARISON OF 1N VIVO A N D

IN VITRO EFFECTS IN THE RAT TESTIS

S. C. LLOYD, D. M. BLACKBURN and P. M. D. FOSTER Imperial Chemical Industries plc, Central Toxicology Laboratory, Alderley Park, Macclesfield,

Cheshire SKI0 4TJ, England

Introduction

2,2,2,-Trifluoroethanol (TFE) is a volatile solvent used in heat exchangers. In the rat it has been shown to produce damage to spermatogonia and sper- matocytes as early as 8 hours after a single ip dose of 25 mg/kg. TFE is mainly excreted in the urine of the rat as the glucuronide, with some trifluoroacetic acid (TFAA: 10-20%), indicating oxidative metabolism via triftuoroacetaldehyde (TFALD).

The purpose of the study reported here was to characterize the testicular effects of TFE both in vivo and in vitro and to investigate the role played by the two oxidative metabolites, T F A L D and TFAA.

Results

Both TFE and TFALD caused a dose-related reduction in testis weight 3 days after a single oral dose, whereas TFAA had no effect on testis weight. The reduction in testis weight was accompanied by morphological changes, involving specific damage to late pachytene spermatocytes after a dose of 10 mg TFE/kg, and also involving spermatogonia and early spermatocytes at 25 mg TFE/kg. T F A L D produced

similar effects to TFE, although at 10mg/kg the damage seemed to be slightly more extensive.

A Sertoli-germ cell culture system has been estab- lished to investigate the effects of toxicants on the testis. In this in vitro system, only T F A L D produced dose-related effects. Morphologically, T F A L D re- suited in a loss of pachytene spermatocytes from the monolayer at 10 -3 and 10 -4 M, but not at 10-SM. At 10-3M neither TFE nor TFAA caused changes in comparison with control cultures. T F A L D also pro- duced a dose-related increase in cell loss compared with the control at concentrations of 10 -4 and above (Fig. la). Leakage of the pachytene spermatocyte marker enzyme, lactate dehydrogenase X (LDHX) paralleled cell loss, being increased in a dose-related manner at 10 -3 and 10-4M-TFALD (Fig. lb).

Conclusions

T F A L D is a potent testicular toxicant and is probably responsible for the lesion produced by TFE in vivo. The initial lesion seen both in vivo and in vitro is specific for late pachytene spermatocytes. The lesion produced is similar to that seen with

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.9

E

o

a) (,.)

e - ( o )

5 -

4 -

3

2 -

0

C o n t r o l

35o (b l

T F A L D

_~ 2SO

==

'~ 150

g o

100

X i 5o

0 f 'A fl T F E T F A A C o n t r o l

Concn (MI

TFE TFAA

Concn (M)

TFALD

Fig. 1. (a) Cell loss and (b) lactate dehydrogenase X leakage from Sertoli-germ cell cultures treated with trifluoroethanol (TFE), trifluoroacetic acid (TFAA) or trifluoroacetaldehyde (TFALD).

653

654 S.C. LLOYD et al.

2-methoxyethanol (ethylene glycol monomethyl ether) and its oxidative metabolites, methoxy- acetaldehyde and methoxyacetic acid, although in vivo TFALD and TFE seem to be much more potent, producing the same lesion at much lower doses. In vitro, TFALD is only slightly more potent than methoxyacetaldehyde. It is interesting that although methoxyaeetic acid will cause spermatocyte damage

both in vivo and in vitro, TFAA does not. This may be due to differences in the inherent toxicity of the two acids, or to differences in metabolism between the two series of compounds.

This structure-activity relationship may help in predicting whether other low-molecular-weight alco- hols metabolized by the same route could produce a similar type of testicular lesion.