Urinary Polyamine Excretion During Growth and Regression of 7,12-Dimethylbenz[a]anthracene-Induced Rat Mammary Carcinoma

Abstract

The correlation of urinary excretion of polyamines and tumor mass was examined with the use of a controlled experimental model. Mammary carcinoma growth was induced in Sprague-Dawley virgin rats by intragastric administration of 7,12dimethylbenz[a]anthracene. Tumors were palpable after about 45 days. After a period of growth, regression of the estrogen-dependent tumors was induced by bilateral ovariectomy. Tumor volume and 24-hour urinary excretion of polyamines were measured during the course of tumor growth and regression. Urinary polyamines were analyzed after acid hydrolysis to determine the total amount of bound and free polyamines. Putrescine excretion followed closely the changes in tumor volume during the course of tumor growth and regression. Urinary spermidine excretion, however, remained essentially unchanged in ovariectomized rats; spermine was barely detectable in any of the urines. There was a high positive correlation between the 24-hour urinary putrescine excretion and urine volume. In nonovariectomized rats. the mammary tumor(s) continued to grow. An unexpected result of the advanced tumor progression was that urinary excretion of both putrescine and spermidine decreased steadily with time as did urine volume. This phenomenon may be due to the fact that tumor-bearing rats develop a state of overt malnutrition, involving complex disturbances of the host metabolism, manifested in decreasing body weight.