Effect of Tar on Experimental Teratoids in the Rat.

Abstract

Carrel, 1 White, 2 Fisher, 3 and others obtained metastasising sarcomata by injecting into fowls a mixture of embryo pulp and dilute arsenious acid or embryo in combination with tar. In a previous publication, 4 it was found that rat embryo combined with arsenic did not produce malignant growths in the rat, and so far as determined, the arsenic did not influence favorably the development of teratoids. In the present experiments, coal tar in various dilutions was combined with embryo pulp to determine its effect on teratoid growth.

From a thick ether extract of coal tar a 1-1000 stock dilution was made in a 5% gelatin and from this the various higher dilutions were made by mixing with one per cent gelatin. Usually about one-half an embryo was drawn directly into a syringe fitted with a needle having a 1-mm. lumen and in the syringe mixed with an equal volume of the tar dilution. The injections into the subcutaneous groin tissue followed immediately. The rats averaged three-quarters grown.

Several factors influence the development of teratoids. The genetic relationship of the animals no doubt, is an important variant in an in-bred strain of animals, such as the one used in these experiments. However, when a 1-500,000 strength of tar was used (experiment 9) all rats showed distinct teratoid growth. When the embryo pulp was mixed with 1-200,000 tar, the teratoid growth took place irregularly and often failed. With tar concentrations of 1-25,000 (experiments 2, 3, and 8) no proliferation of the embryonic cells was demonstrable.

Embryonic rat cells brought into contact with tar have shown no tendency to undergo malignant transformations. The only influence observed was an inhibition of teratoid development by the tar in the greater concentrations.