[Inhibiting effect of thymogen on the development of tumors of the esophagus and forestomach induced by N-nitrososarcosine ethyl ester in rats].

Immunostimulating synthetic peptide thymogen being an analog of the thymus polypeptide drug thymalin was studied for its effect on carcinogenesis of the esophagus and forestomach in male rats. Rats received N-nitrososarcosine ethyl ester (NSEE) per os in the daily dose of 100 mg/kg of body weight during 8 weeks. After cessation of the carcinogen administration rats were treated with thymogen (the daily dose of 10 micrograms per rat) or immune-inactive polypeptide drug pulmolin from the alveolar tissue of lung (the daily dose of 0.5 mg per rat) during the following 32 weeks. Animals were killed 40 weeks after the experiment beginning. NSEE induced the esophagus and forestomach tumours, mainly papillomas and rarely carcinomas, practically in all rats, more than 5 tumours per rat, on the average. Thymogen decreased the tumour incidence by 12% and made tumour multiplicity 1.7 times as low. Pulmolin did not influence development of these tumours.