Protein digestion in isolated lysosomes inhibited by intralysosomal trypan blue

Control rats and rats treated with subcutaneous trypan blue were injected intravenously with denatured albumin-I(125). Lysosome-rich fractions of their livers, when incubated at 22 degrees C in osmotically protected medium (pH 7.4), retained their capacit to digest albumin-I(125). The rate of digestion was lower in suspensions pre-pared from rats treated with trypan blue than in control suspensions, but rates of lysosome breakage were not different. T'hese results and other experimental evidence suggest that trypanblue concentrated within lysosomes can inhibit intralysosomal digestion, probably by inhibition of lysosomal proteinases.

Methods for the Study of Embryotrophic Nutrition

In Early post-implantation stages of development, before the establishment of an intimate relationship between the maternal and foetal circulations, embryonic nutrition is carried out largely by the breakdown of macro-molecules in certain phagocytic extra-embryonic membranes. This communication is concerned with defining histochemica, electron microscopic and biochemical parameters which make it possible to identify the membranes concerned. In vivo and in vitro systems for the measurement of the amount of macromolecular breakdown occurring in certain foetal membranes are presented. It is suggested that interference with these catabolic processes may produce congenital malformations or result in abortion of the conceptus.

Lysosomal enzyme inhibition by trypan blue: a theory of teratogenesis

A mechanism of mammalian teratogenesis involving inhibition of embryotrophic nutrition is suggested and exemplified by the action of trypan blue on pregnant rats. There is evidence for the localization of trypan blue in heterolysosomes of the epithelium of the visceral yolk sac, and our experiments indicate that the dye is an inhibitor of a selection of hydrolytic enzymes present in lysosomal fractions from homogenates of rat visceral yolk sac. It seems likely that trypan blue inhibits the intracellular digestion of embryotroph by the visceral yolk-sac epithelium; the conceptus may therefore be deprived of essential nutrients at critical stages of development.

A histochemical and biochemical study of some aspects of placental function in the rat using maternal injection of horseradish peroxidase

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The relationship of chemical structure to teratogenic activity among bisazo dyes: a re-evaluation

Although the potency of trypan blue as a teratogenic agent in rodents has been known for almost twenty years the mechanism of its action remains obscure. The dye produces a variety of biological effects (see review by Beck & Lloyd, 1966) and most of these have at some time been suggested as possibly relevant to its teratogenicity. The investigation of such correlations would clearly be assisted by determining whether the biological effects of the dye are individually modified by small changes in its chemical structure, particularly if these changes also result in differences in its teratogenicity.

The first teratological study of dyes related to trypan blue was made by Gillman, Gilbert, Spence & Gillman (1951), who obtained negative results in rats with six dyes (methylene blue, trypan red, Sudan IV, Bismarck brown, Niagara blue and sky blue), but gave no experimental details of their investigation.

The Preparation and Teratogenic Properties of Pure Trypan Blue and its Common Contaminants

Trypanblueisthe sodium salt of the bluedisazo dye prepared by coupling tetrazotized o-tolidine with two molecular proportions of 8-amino-l-naphthol- 3, 6-disulphonic acid (Hartwell & Fieser, 1936). Its structural formula is:The dye has been extensively used as a vital stain, particularly for the cells of the reticulo-endothelial system and of the proximal convoluted tubule of the kidney.

Recently (Gillman et al., 1948) it was shown that trypan blue, when injected into pregnant rats, caused a considerable foetal mortality and produced deformities in a substantial proportion of the survivors. The effect of such an injection varied with the stage of pregnancy at which it was given, and injection on the ninth day (counting the 24-hour period after copulation as the first day of pregnancy) was found to produce the greatest number of malformations (Wilson et al., 1959). Later it was shown that the strain of rat used affected the percentage of deformed young produced (Gunberg, 1958; Tuchmann-Duplessis & Mercier-Parot, 1959; Beck et al., 1960).