Ovarian tumours and other ovarian changes induced in mice by two 19-nor-contraceptives

Pharmacology and toxicology of ethinyl estradiol and norethindrone acetate in experimental animals

For over 30 years various combinations of synthetic estrogens and progestins have been used in oral contraceptive formulations. Ethinyl estradiol (EE) and norethindrone acetate (NA) are common synthetic hormones used in oral contraceptives such as Loestrin, Brevicon, Ortho-Novum, Norlestrin, and Norinyl. In recent years these oral contraceptives have been considered for development in other therapeutic indications. Given the use of these agents for other clinical indications with different and larger target populations, an updated comprehensive review of the toxicology literature of estrogens and progestins is warranted. This review will summarize available data on the pharmacology and toxicology of estrogens and progestins with an emphasis on the specific synthetic hormones EE and NA. Ethinyl estradiol and norethindrone acetate alone or in combination, possess low acute and chronic toxicity. In some studies, EE and/or NA increased the incidence of specific tumors in susceptible strains of rodents and dogs, but not monkeys. These agents are not teratogenic when given in combination. Alone EE and NA have clastogenic properties. Overall, the animal data demonstrates that long-term exposure to EE and NA formulations pose very little health risks to humans.

Modulatory influence of oral contraceptive pills Ovral and Noracycline on 3-methylcholanthrene-induced carcinogenesis in the uterine cervix of mouse

The present study reports the modulatory influences of combined oral contraceptive formulations, Ovral (0.05 mg ethinylestradiol plus 0.5 mg norgestrel per pill) and Noracycline (0.05 mg ethinylestradiol plus 0.1 mg lynestrenol per pill), on methylcholanthrene (MCA)-induced carcinogenesis in the uterine cervix of Swiss albino mouse. Placement of cotton thread impregnated with beeswax containing approximately 300 micrograms of MCA yielded cervical tumors in 0.0%, 8.6% and 26% animals, respectively, in 30, 60 and 90 days. Concomitant treatments with doses D1 (1/2000th of a pill), D2 (1/200th of a pill) and D3 (1/20th of a pill) of Ovral yielded cervical tumors in 0.0%, 0.0% and 4.5% mice at 30 days, 0.0%, 6.2% and 10% mice at 60 days and in 3.3% (P less than 0.05), 3.4% (P less than 0.05) and 47% mice at 90 days, respectively. Likewise, concomitant treatments with doses D1 (1/2000th of a pill), D2 (1/200th of a pill) and D3 (1/20th of a pill) of Noracycline yielded cervical tumors in 0.0%, 0.0%, 16.6% mice at 30 days, 4%, 3.7% and 54% (P less than 0.05) mice at 60 days and 3.2% (P less than 0.05), 20% and 63% (P less than 0.05) of mice at 90 days, respectively. Both Ovral and Noracycline displayed biphasic action on MCA-induced cervical carcinogenesis in mice. At lower dose levels (D1 and D2), they were inhibitory while at the higher dose level (D3) they were augmentatory in their actions. Both pills also significantly enhanced the incidence of cervical hyperplasia.

Modulatory influence of injectable contraceptive steroid medroxyprogesterone acetate on methylcholanthrene-induced carcinogenesis in the uterine cervix of mouse

Methylcholanthrene (approximately 300 micrograms) plus beeswax-impregnated thread, when placed inside the canal of the uterine cervix of virgin female adult mice for 30, 60 and 90 days produced cervical tumors in 0.0, 10 and 30% of mice, respectively. Employing this experimental cervical carcinogenesis model system, the present study evaluated the modulatory influence of medroxyprogesterone acetate (MPA) on the incidences of precancerous and cancerous lesions in the cervical epithelium as well as on phase I and phase II drug metabolizing enzymes and acid soluble sulfhydryl level in the liver. Intramuscular administration of MPA (50 micrograms every 5th day) to the carcinogen-thread inserted mice for 30, 60 and 90 days produced cervical tumors respectively in 0.0, 13.3 and 60.5% (P less than 0.05) of mice. A significant increase (P less than 0.05) in hyperplasia was also observed in the present study. A significant decrease in cytochrome b5 was found after 30 days.

Carcinogenicity of some anticancer drugs--a survey

A list of 37 anticancer drugs with reported carcinogenicity or co-carcinogenicity has been compiled. These drugs include 16 alkylating agents, eight antimetabolites, four antibiotics, four hormones, one alkaloid, and four miscellaneous drugs. The reported carcinogenicity of these drugs in model systems and their possible mechanisms of action are reviewed together with structure-carcinogenicity relationships. These drugs have been reported to cause cancers in different sites in various test animals. Most of these drugs react with DNA, and the ultimate reactive forms of the drugs are electrophiles.

Studies of the components of an oral contraceptive agent in albino rats. II. Progestogenic component and comparison of effects of the components and the combined agent

Albino rats were fed norethindrone acetate in the diet for 2 yr at dosage levels (0.3--0.4 mg/kg) of about 10 and 100 times the recommended human dose as used in a combination estrogen-progestogen oral contraceptive. The treated rats had dose-related growth retardation and alopecia, but an enhanced survival rate. Dose-related changes in the male rats included testicular and accessory gonadal atrophy, and in the females, uterine changes. In animals of both sexes at the high dose level, there was liver enlargement with increased foci of cell alterations and cystic mastopathy. Females had increased adrenal gland weights, decreased ovarian weights, and ovarian atrophy. Females at both dose levels had an increased incidence of uterine polyps, and rats of either sex in the high-dose group had an increased incidence of liver neoplastic nodules. However, there were no significant differences with respect to tumor incidence, probability of tumor development, or number of tumors developing in treated compared to untreated rats. In fact, in the females there was a delayed onset of tumor formation.

Evaluation of the carcinogenic effects of estrogens, progestins and oral contraceptives on cervix, uterus and ovary of animals and man

Estrogens do not have the general biological effect of increasing the occurrence of cancer in various species of laboratory animals. The neoplastic effect of estrogens in animals is strain and species dependent. Estrogens may increase the incidence of uterine cervical cancer in some strains of mice, but not in other strains or other animal species. The progestins and oral contraceptives (OC) have not induced cervical cancer in animals and most studies demonstrate that the steroid anovulants do not increase the occurrence of abnormal cervical smears or cervical cancer in women. Estrogens increase the occurrence of endometrial cancer in the rabbit, occasionally in the mouse, but apparently not in other species. Case-control studies in menopausal and postmenopausal women indicate an increased risk of endometrial carcinoma (EC) associated with use of estrogen. However, in other studies estrogen has not been related to EC. Cases of EC have been reported in women using sequential OC but a causal relationship has not been established. Progestins alone may arrest progress or cause regression of EC in women. EC has not been related to use of the combination OC, and it is unlikely that use of these anovulants will lead to the development of endometrial cancer. Estrogens or OC do not induce a carcinogenic response in the ovary. A decrease in ovarian cysts, is observed during the clinical use of OC.

[Chlormadinone-induced changes in the proliferative activity of Ehrlich ascites tumor]

The effect of Chlormadinone on the proliferation of Ehrlich ascites tumour was studied by employing the stathmokinetic method. In a high percentage of female mice carrying the tumour and treated by Chlormadinone an increase in tumour cell proliferation was observed, while in a few animals the proliferative activity was decreased.

No significant changes were observed in tumour cell proliferation in the male mice.