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The Effect of Small Doses of Prednisolone on the Incidence of Subcutaneous Sarcomas Induced by 3-Methylcholanthrene in Virgin Female Swiss Mice

Department of Pathology, Jinnah Postgraduate Medical Center, Karachi, Pakistan

The effect of small doses of prednisolone on the incidence of chemically induced subcutaneous sarcomas by 3-methylcholanthrene in virgin female Swiss mice was studied. Each animal received, in the middle of its back, a single s.c. injection of 2 mg of 3-methylcholanthrene dissolved in 0.3 ml of trioctanoin. Dosages of 0.083, 0.050, and 0.035 mg of prednisolone contained in 0.05 ml of normal saline were given by daily i.p. injections to all the test animals for 20 weeks. Each of the control animals received i.p. injections of 0.05 ml of normal saline daily for the same period. The animals were weighed at weekly intervals. Animals from the test group showed a 7% decrease in body weight from the 2nd to the 6th week. Later these animals gained in weight at the same rate as the control animals. This subsequent increase in weight in the prednisolone-treated animals was not related to any obvious evidence of edema. Three animals of the control group presented tumors at the end of the 6th week, whereas the 1st sarcoma in the test group was detected on palpation at the end of the 10th week. All tumors were allowed to grow for a further period of 2 weeks following their initial recognition. The respective animals were then sacrificed and sections of the masses examined under the microscope. The experiment was terminated at the end of 20 weeks. All of the 23 surviving control animals developed tumors by the end of the 16th week. Thus there was a 100% yield of tumors in the control group of animals; on the other hand, only 20 of the 35 surviving test animals developed tumors, so the yield of tumors in the test group of animals was only 57.1%. This highly significant inhibitory effect of prednisolone on tumorigenesis was apparently also reflected in the size and histologic appearances of the tumors. The tumors in the prednisolone-treated group were smaller and appeared histologically less malignant.

¹ Submitted in partial fulfilment of the requirements of the Master of Science degree.

² Present address: Fatima Jinnah Tuberculosis Sanatorium, Quetta, West Pakistan.

Received 7/ 1/65. Revised 1/19/66.