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At least 217 records · Page 12Linked to original sources
PubMed1979

Inhibitory effect of prostaglandin F2 alpha on the growth of a hormone-dependent rat mammary tumor.

Growth of the rat hormone-dependent mammary adenocarcinoma MTW-9 was inhibited by prostaglandin F2alpha (PGF2alpha) This inhibition of tumor growth was associated with a marked reduction in serum progesterone concentrations. The inhibitory effect of PGF2alpha on tumor growth was abolished by concomitant injections of progesterone. The growth rates of coimplanted prolactin-secreting pituitary tumor MtTW-5 and plasma concentrations of prolactin and estradiol were not affected significantly by PGF2alpha. Our data imply that the effect of PGF2alpha on growth of rat mammary adenocarcinoma is mediated by progesterone.

Adenocarcinoma↗
PubMed1979

Synergism of diethylstilbestrol and radiation in mammary carcinogenesis in female F344 rats.

One compressed 20-mg pellet containing cholesterol only or cholesterol mixed with 0.98, 1.6, 2.6, or 3.9 mg of diethylstilbestrol (DES) was implanted into each of 203 female F344 rats. Two days later, half the animals in each group were exposed to 150 R of X-rays, and the other half were sham irradiated. The rats were maintained until 350 days post implantation. Mortality increased with the higher doses of DES, with or without X-rays. DES at all dose levels, with or without X-rays, produced pituitary tumors and pyometritis. Only rats that received both DES and X-rays had mammary adenocarcinomas (AC). A synergistic AC response was found in the group that received 2.6 mg DES plus X-rays. Synergism was defined as a significantly greater incidence of rats with mammary neoplasia resulting from DES plus X-ray treatment when compared to the summed incidence from comparable individual treatments. For all other groups of rats that received both treatments, synergism was detected only when their data were combined. Synergism was not detected among rats that had fibroadenomas (FA). Both types of neoplasms were independent phenomena because no significant relationship was found between the incidences of FA and AC.

Adenocarcinoma↗
PubMed1980

Synergism of diethylstilbestrol and other carcinogens in concurrent development of hepatic, mammary, and pituitary tumors in castrated male rats.

Castrated male WF rats, given implants of pellets containing 5.0 mg diethylstilbestrol (DES), were given N-butyl-N-nitrosourea (NBU) in small amounts, which alone produced no mammary tumors in intact female rats. Treatment resulted in the high yield of hepatic tumors (HT), mammary tumors (MT), and pituitary tumors (PT) concurrently in each rat. If animals were further treated with prolactin, the development of HT and MT was accelerated, whereas that of PT was suppressed. None of the intact or castrated rats receiving NBU and/or prolactin developed tumors in any tissues if DES treatment was omitted. Exposure of male rats, preconditioned similarly to NBU treatment, to 200 rads of 14.1-MeV fast-neutron radiation also elicited HT, MT, and PT with an efficiency comparable to that of NBU-treated rats. These findings indicate that DES played an essential role in the whole carcinogenic process in each tissue and that castrated male rats, if conditioned properly with estrogens, are useful for the study of the carcinogenesis mechanism in these tissues.

Animals↗
PubMed1978

Effects of radiation type and dose and the role of glucocorticoids, gonadectomy, and thyroidectomy in mammary tumor induction in mammotropin-secreting pituitary tumor-grafted rats.

Three experiments on the induction of mammary neoplasms by total-body 11- to 100-rad neutron or 50- to 500-rad gamma-radiation of female Fischer or W/Fu rats are reported. Grafts of mammotropin-secreting pituitary tumor were used to elevate mammotropic hormone levels. The results (a) confirm and extend previous reports that neutrons are more efficient in carcinoma induction than are gamma-rays (the neutron relative biological effectiveness for first carcinomas was 3.68) and (b) demonstrate that the potentiation of carcinoma induction by adrenalectomy is reversed by glucocorticoid replacement. Statistical analysis of the data by procedures that take into account time at risk as well as tumor frequency indicates that multiple mammary tumors do not occur independently (i.e., a first mammary neoplasm significantly increases the probability of development of another neoplasm). The statistical procedure used in this analysis is presented.

Adrenal Glands↗
PubMed1983

Induction of angiogenic tumors in the duodenum of female Donryu rats by continuous oral administration of N-isobutyl-N-nitrosourea.

Four groups of female Donryu rats were continuously given 400, 200, 100 or 0 ppm N-isobutyl-N-nitrosourea (iso-BNU) in their drinking water, and were examined for the development of tumors. The incidence of digestive tract tumors was 25/28 (89%), 14/24 (58%), 6/25 (24%) and 0/17 (0%), in the 400, 200, 100 and 0 ppm groups, respectively. The predominant type of digestive tract tumor was angiogenic, and a few were of the epithelial type. A dose-effect relationship was clearly demonstrated not only in the incidence of digestive tract tumors but also in the average survival period of rats with these tumors.

Administration, Oral↗
PubMed1980

The biological significance of estradiol receptor binding to DNA.

MTW9-D, a rat mammary tumor derived from MTW9 by chronic administration of the dopamine antagonist drug R33,812 shows ovariectomy-induced regression (OIR). MTW9-MtT is also a variant of MTW9, grown by coimplantation of a mammosomatotropic tumor MtTW10, but it does not show OIR. However, when the mammosomatotropic tumor (MtT) is resected, the tumor regresses and shows rapid OIR; implantation of MtT into animals bearing MTW9-D prevents OIR following drug withdrawal. The estradiol receptor (ER) from MTW9-D cytosol binds to DNA-cellulose significantly more than that from MTW9-MtT. After MtT resection, the mammary tumor ER binds to DNA-cellulose, as well as ER from MTW9-D, whereas implantation of MtT into animals bearing MTW9-D decreases ER binding to DNA-cellulose. The significance of these findings in relation to possible clinical application is discussed.

Animals↗