The Effects of the Carcinogen, 2-Acetylaminofluorene, on Larval and Adult Frogs

Abstract

2-Acetylaminofluorene is a po\verful carcinogen capable of inducing a variety of benign and malignant neoplasms in several species of anirl~als ancl is required only in very small amounts for relatively short periods of time. I t is sorne\\rhat sol~rble ( 1 . 3 rllgm. per 100 cc.) in water. Frog taclpoles \\,ere raised in solutions of various strengths. Even dilute solutions proved to be highly toxic to these animals. In those animals that sur\;ived it was found that 2-acetylaminofluorene inhibits both total body growtll ancl rate of tail regeneration; that the tadpoles remninetl dark (melanophores clilatecl) even on a light backgro~rnd; that lesions of the liver developed resembling those described in mammals resulting from treatment with the same and other carcinogens. It is not certain that these lesions are neo,plastic, but they may be of the type that precede or accompany liver cell carclnonla. This carcinogen \\.as also fed to or injected into adult frogs. E\.en small amounts \\-ere toxic to them and only a small nunlber survivetl for Inore t-han a few days. In the survi\rors, after six to eight n:eel;s, lesions of thc liver, including necrosis and cirrhosis, appeared. No distinct rleoplasrns were produced.The present investigation represents a study of the effects of a ltnown carcinogenic substance upon both larval and adult frogs in an attempt to produce neoplasia in these animals. Materials and MethodsThe carcinogen used in this investigation was 2-acetylaminofluorene (Eastman I<odalt Co.). I t is capable of inducing a variety of benign and malignant neoplasms in several species of animals. I t is required in very small amounts for relatively short periods of time. I t is somewhat soluble in water, 1 . 3 mgm. dissolving in 100 cc. (12,56). In some instances 2-aminofluorene was used. I t is similar in its action but is more soluble in water (3.0 mgm. per 100 cc.).Large mature R a n a pipiens obtained from the Carolina Biological Supply Co. were used in the production of eggs. Large numbers of eggs may be obtained and successfully fertilized by the method of Rugh (49) from September to April. The eggs thus obtained were raised in finger bowls, about 20 eggs in each, in t a p water a t room temperature. When the tadpoles were well established (three to four weelts of age) treatment with the carcinogen was begun.Even under uniform environmental conditions the tadpoles arising from a given egg mass show considerable variation in their degree of development a t any given time (46,53). For this reason only tadpoles of approximately the same size and a t the same stage of development mere selected for treatment with the carcinogens and as controls.Tadpoles were maintained in glass finger bowls such that there mas about 100 cc. of solution for each animal. The solutions were changed every other day, and, a t the same time, the finger bowls were washed in warm soapy water. Each tadpole, therefore, had the opportunity of absorbing 3-4 mgm. of the carcinogen per week. The tadpoles were fed fresh canned spinach in sm...