E. Ertürk

Production of Urinary Bladder Carcinomas in Mice by Sodium Saccharin

Pellets weighing 20 to 24 milligrams and containing 20 percent sodium saccharin suspended in cholesterol were surgically implanted into the urinary bladder lumens of female Swiss mice (60 to 90 days old) under ether anesthesia. Incidences of mouse bladder carcinomas in animals exposed to these pellets were 47 and 52 percent as compared with incidences of 13 and 12 percent in control mice exposed to pellets of pure cholesterol. The exposure of the mouse bladder to saccharin was very brief, because the time required for 50 percent of the compound to be eluted from the pellets was about 5.5 hours.

Production of Mouse Urinary Bladder Carcinomas by Sodium Cyclamate

Sodium cyclamate was suspended in cholesterol pellets that were surgically implanted in the urinary bladders of mice. In duplicate experiments, incidences of mouse bladder carcinomas observed in animals exposed to these pellets were 78 and 61 percent compared with incidences of 13 and 12 percent in control mice exposed to pellets of pure cholesterol. The exposure of the mouse bladder to sodium cyclamate was very brief, as the time required for 50 percent of the compound to disappear from the pellets was about 1 hour. This experimental technique was found to be highly sensitive, reproducible, and predictive of the bladder carcinogenicity of orally administered cyclamate.

Induction of mammary tumors, estrous cycle abnormalities and endometrial hyperplasia in rats exposed to different doses of N-nitrosomethylurea☆

Groups of female Sprague--Dawley strain rats were given 3 i.v. injections of N-nitrosomethylurea in doses of 0.5, 1, 2, 3, 4 or 5 mg/100 g body weight at 4-week intervals. The first dose was given when they were 50 days old. By 23 weeks after the first injection, mammary tumors had developed in 0, 0, 33, 54, 72 and 100% of animals respectively. There was a direct relationship between the total dose of carcinogen administered and the degree of tumor anaplasia observed on histological examination. All of the tumors contained assayable amounts of estrogen and progesterone receptors, and the receptor concentrations were not related to the dose of carcinogen. Twenty-one rats, all exposed to the 4 highest doses of N-nitrosomethylurea, had arrest of the estrous cycle at the stage of estrus. In 15 of the 21 the walls of the uterine horns were thickened and grossly distended by fluid. Histological examination demonstrated the presence of endometrial hyperplasia. These uterine abnormalities were usually accompanied by polycystic disease of the ovaries. Both endometrial hyperplasia and abnormal estrous cycles without uterine changes were associated with elevated progesterone receptor to estrogen receptor ratios in the corresponding mammary carcinomas.

Effects of 4(5)-(3,3-dimethyl-1-triazeno)-imidazole-5(4)-carboxamide (NSC 45388) in proliferating rat tissues

Abstract Some effects of 4(5)-(3,3-dimethyl-1-triazeno)imidazole-5(4)-carboxamide (DIC) on normal proliferating tissues in rats were described. DIC caused marked but transient inhibition of labeled thymidine incorporation into DNA and presumably DNA synthesis of thymus, regenerating liver, spleen and small intestine. The inhibition was reversible and its duration dose dependent. When incorporation of precursors into DNA was markedly inhibited, no consistent concomitant effect on incorporation of precursors into RNA or protein was observed. Karyorrhectic cells appeared in the intestinal crypts as well as signs of necrosis in the thymus after administration of 125 mg/kg of DIC, but no significant pathologic changes were found in the spleen or regenerating liver. The relationship between selective inhibition of DNA synthesis and cytotoxic effect was observed.

Effect of progesterone administration on rat endometrial disease after exposure to N-nitrosomethylurea.

WE RECENTLY reported the occurrence of estrous cycle abnormalities, polycystic disease of the ovaries, gross thickening of the uterine horns with accompanying hydrometria and endometrial hyperplasia in rats exposed to the mammary carcinogen N-nitrosomethylurea [ 11. Eventually a proportion of these animals develop infiltrative adenomatous hyperplasia, squamous metaplasia and carcinomas of the endometrium (unpublished findings). Thus the uterine changes which occur over time after treatment with Nnitrosomethylurea (NMU) appear to provide a useful model for human endometrial cancer. We have now demonstrated low serum progesterone levels in rats exposed to NMU and found that the uterine abnormalities can be prevented by chronic administration of progesterone. Our model, therefore, also reproduces clinical situations in which uterine tissue is exposed to estrogen stimulation unopposed by progesterone. Figure 1 illustrates the low serum progesterone levels and loss of the estrous cycle peak in NMUtreated rats. The carcinogen had been administered by i.v. injection on 3 occasions, the first when the rats were 50 days old, as previously described [Z], except that the dose was 4 mg/lOO g body weight. Serum samples were obtained from 6 NMU-treated rats 4.5 months after the first injection for 5 days between 7:00 and 7:30 p.m., and also from 10 controls. Progesterone was extracted from serum with petroleum ether [3] and measured by radioimmunoassay [4]. To demonstrate an inhibitory effect of progesterone administration on

Effects of reserpine administration on rat mammary tumors and uterine disease induced by N-Nitrosomethylurea

Reserpine 50 μg100 g body weight administered s.c. to female rats on the day before, of and after each of three N-nitrosomethylurea (NMU) i.v. injections, influenced a number of experimental observations. The total doses of NMU given to the various treatment groups were 15, 12, 9, 6, 3 and 1.5 mg100 g body weight. Tumor incidence ranged from approximately 100 to 0% in the control and reserpine-treated groups, depending on the dose of carcinogen given. Concurrent reserpine administration with the NMU decreased the number of tumors per rat; at 15 and 12 mg100 g body weight NMU doses the values were only 58 and 55% of the respective controls. Reserpine treatment at these 2 NMU doses also increased the percentage of well-differentiated mammary tumors compared with corresponding controls. Tumor estrogen receptor levels in controls ranged from 71 to 78 fmol/mg protein and in the reserpine-treated groups from 96 to 105 fmol/mg protein; significant elevations were present in the rats given reserpine and the 2 highest doses of NMU. Tumor progesterone and prolactin receptor levels were similar in control and reserpine-treated groups. The estrous cycle of the controls was frequently arrested at estrus and 2157 (37%) had a fluid-distended uterus and thickened uterine walls; only 252 (4%) of reserpine-treated rats had hydrometria and none exhibited cycle arrest at estrus. The effect of reserpine on mammary tumors was also studied when given after initial exposure to the carcinogen. NMU was administered to 65 rats in 3 doses of 5 mg100 g body weight by i.v. injections 4 weeks apart. Equal numbers of animals comprised 1 control and 2 reserpine treatment groups. Reserpine was given at a daily dose of 20 μg100 g body weight commencing 67 days after the first NMU dose (chronic regimen) or by the same schedule preceded by 50 μg100 g doses given on the day before, with and on the day after the second and third NMU injections (acute/chronic regimen). A fourth group of rats received chronic reserpine treatment but no NMU. All 3 NMU-exposed groups had a 100% tumor incidence; none developed in the reserpine-treated controls. The acute/chronic reserpine treatment increased the rate of tumor development but neither drug schedule altered the number of tumors per rat or the mean final total tumor areas. Reserpine administration was associated with greater degrees of anaplasia in mammary tumors induced by NMU (P < 0.01). The mean tumor estrogen receptor content was significantly higher in the acute/chronic reserpine-treated group (P < 0.0002) and the chronic reserpine-treated animals (P < 0.008) compared with controls. Tumor prolactin receptor content was unaffected by the drug. Peroxidase activity was higher in mammary tumors and lower in uteri from reserpine-treated rats compared with tumor-bearing controls. Also, there was a strong correlation (r = 0.82) between the mammary tumor estrogen receptor and tumor peroxidase activity for rats treated with the acute/chronic reserpine regimen.