Toxicology--Fd Costnet. Toxicol. Vol. 17 No. 6 689

Tests with human DNA have shown that tris-(2,3- was given weekly SC injections of 23 mg PVB in dibromopropyl)phosphate (TRIS) may have genetic aqueous suspension (injection volume 0.05 ml) for effects in eukaryotic cells as well as in bacteria (Cited 48 wk, followed by a 60-wk observation period. in F.C.7: 1979, 17, 98). Moreover, this flame retardant THPC and PVB were inactive when applied to the has been shown to migrate from fabrics during laun- skin, but TRIS induced significant numbers of skin dering (ibid 1976, 14, 512) and to undergo a variable tumours at the site of application and also in other degree of absorption through the skin (ibid 1977, 15, tissues. Some of these tumours, notably several sgua- 257). A close scrutiny of this and similar flame-proof- mous-cell carcinomas of the tongue or the gingival ing compounds proposed for use in clothing fabrics is, area, are rare in these mice and were probably in- therefore, an obvious necessity, and a variety of work duced by grooming. TRIS applications also increased has already been undertaken. significantly the incidence of stomach papillomas. In

A recent report presents the results of a skin addition, both of the TRIS doses applied were associ- application study in mice. Three flame-retardants- ated with a high incidence of papillary tumours of the TRIS. tetrakis(hydroxymethyI)phosphonium chloride lung, and in the 30 mice given the higher dose there (THPC) and polyvinyl bromide (PVB)-were applied was one tubular adenoma of the kidney. Tumours of three times weekly to the skin of female Swiss mice the latter type were previously found in a TRIS feed- for 420-496 days. TRIS was applied in doses of 10 or ing study, although the incidence then was not signifi- 30mg in @2 ml acetone, THPC in 2-mg doses in cant. PVB injections induced liposarcomas in 19 of 30 @2 ml 90% aqueous acetone, and PVB in O.l-ml doses mice, but this was considered to be a physical re- of a 40% suspension. Another group of Swiss mice sponse to the injection of the aqueous suspension.

TOXICOLOGY

Trypan blue teratugenesis

Beck, F., Swidzinska, P. & Gulamhusein, A. (1978). The effect of trypan blue on the development of the ferret and rat. Teratology 18, 187.

Although the potency of trypan blue as a terato- genie agent in rodents has been known for some time (Cited in F.C.T. 1968, 6, 663), the mechanisms in- volved have remained somewhat obscure. In rats, congenital malformations do not occur if the com- pound is given on or after gestation day 11.5 (Wilson rr al. Amt. Rec. 1959, 133, 115) the time at which a functional chorio-allantoic placenta is established. It is thought that the teratogenic effects of the com- pound at 8.5 days are due to interference with the histiotrophic function of the inverted yolk-sac endo- derm (Williams et al. Teratology 1976, 14, 343). The above-cited study compares the effects of trypan blue in rats with those observed in the ferret, in which species histiotrophic nutrition does not involve an in- verted yolk-sac system and is still of great importance at a relatively late stage of embryonic development.

Wistar rats received a dose of 1OOmg trypan blue/kg SC at either 8.5 or 11.5 days of gestation. The ferrets received either 25 or 50 mg/kg SC on day 13 or 18. so that both species were treated at comparable stages of embryonic development. As expected. ad-

ministration to rats on day 8.5 of gestation resulted in high abnormality rates, but there was a negligible ter- atogenic effect when the compound was given at 1 I.5 days. In contrast, the ferret showed a high malforma- tion (and resorption) rate following trypan blue ad- ministration at both 13 and 18 days of gestation. The types of malformation differed in the two species, with absence or deformity of the tail and malformations of the CNS predominating in the rat, and palatal non- closure and omphalocoele being the most common malformations in the ferret.

On the basis of these results, four suggestions are put forward to explain the mechanism of teratogenic action in the ferret. Considered by the investigators to be the most convincing is the possibility that the pres- ence of trypan blue in tissue fluid inhibits the phago- cytic action of the invading trophoblast of the ferret, as it inhibits pinocytosis by the yolk-sac epithelium of the rat. Alternatively pathological changes produced in the mother may be sufficiently severe to produce embryopathy in the ferret but not in the rat. A third suggestion is that the high incidence of cleft palate in the ferret may be part of a general pattern of delayed growth rather than a special effect in itself. Finally, although the dye cannot be seen in embryonic tissue with the light microscope, it is still possible that small protein-bound quantities are present in sufficient amounts to exert a teratogenic effect.