Effects of progesterone, ovariectomy and adrenalectomy on mammary tumours induced by 7,12-dimethylbenz(a)anthracene in sprague-dawley rats

Jabara, Anne G.; Harcourt, Alison G.

doi:10.1080/00313027109073735

Cited by 9 publications

(7 citation statements)

References 11 publications

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“…However, statistically the enhancing effect of progesterone on latent period (tumour incidence) in hypothyroid rats was equivalent to that previously observed in entire DMBAtreated animals (Jabara, 1967;Jabara and Harcourt, 1970). Progesterone administration did not modify-tumour growth behaviour in hypothyroid rats; a similar finding was observed previously when progesterone was given to the controls (Jabara and Harcourt, 1970).…”

Section: Discussionsupporting

confidence: 90%

“…As has been observed previously in entire rats (Jabara and Harcourt, 1970), in Group 1 and 2 neoplasms arose equally on both sides and most tumours were in the anterior 3 pairs of glands.…”

Section: Locations and Types Of Tumnourssupporting

confidence: 87%

“…Continuous progesterone administration to hypothyroid rats increased DMBA tumorigenesis compared with hvpothyroidism alone, although the tumour yield was still significantly lower and the latent period significantly longer than in the control groups treated with DMBA, either alone or combined with progesterone (Jabara and Harcourt, 1970). However, statistically the enhancing effect of progesterone on latent period (tumour incidence) in hypothyroid rats was equivalent to that previously observed in entire DMBAtreated animals (Jabara, 1967;Jabara and Harcourt, 1970).…”

Section: Discussionsupporting

confidence: 66%

“…Progesterone, while not carcinogenic per se, significantly enhances DMBA mammary tumorigenesis in entire rats when hormone injections are begun just before or after carcinogen administration (Jabara, 1967;Jabara and Harcourt, 1970). By contrast, ovariectomy performed 7 days before feeding DMBA totally inhibits mammary tumour development (Jabara and Harcourt, 1970) whereas adrenalectomy has no significant effect on tumorigenesis (Jabara and Harcourt, 1971). Reported effects of hypothyroidism on mammary tumour induction range from an enhancement of carcinogenesis Thomas, 1966, 1967;Davidson, Owen and Thomas, 1969) to a reduction (Helfenstein, Young and Currie, 1962; Cameron, Owen and Thomas, 1970;Kellen, 1972); Gruenstein et al (1968) found hypothyroidism to be without apparent effect on tumour development.…”

Section: Induction Of Mammary Tumours Bymentioning

confidence: 99%

“…The present experiments were undertaken to determine the effects of hypothy- (Jabara and Harcourt, 1970 Beginning 4 weeks after DMBA administration, all rats were palpated weekly and any mammary tumours recorded, measured and graphed as described previously (Jabara, 1967).…”

Section: Induction Of Mammary Tumours Bymentioning

confidence: 99%

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Effects of Hypothyroidism and Progesterone on Mammary Tumours Induced by 7,12-Dimethylbenz(a)anthracene in Sprague-Dawley Rats

Jabara¹,

Maritz²

1973

Br J Cancer

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Summary.-Hypothyroidism, alone or combined with progesterone, significantly decreased 7,12-dimethylbenz(a)anthracene (DMBA) mammary tumorigenesis relative to controls. However, the decrease was less in the progesterone-treated group, and statistical analysis showed that progesterone enhanced tumorigenesis to the same extent in hypothyroid animals as in the controls. Most tumours in hypothyroid progesterone-treated rats were adenocarcinomata; in the absence of the hormone most tumours were benign. However, the difference between the tumour types in the 2 groups was not statistically significant.The morphological changes observed in the endocrine glands, genital tracts and non-neoplastic mammary tissue, considered in relation to previously reported data, suggest that hypothyroidism reduced the tumour yield mainly by secondarily inhibiting somatotrophin production and secretion, although the effect of decreased food intake could not be excluded completely. The higher tumour yield in the hypothyroid progesterone-treated rats may have been due to higher circulating levels of prolactin in this group compared with those in the hypothyroid group which received no hormone. INDUCTION of mammary tumours by7,12-dimethylbenz(a)anthracene (DMBA) is influenced markedly by the hormonal environment of the animal. Progesterone, while not carcinogenic per se, significantly enhances DMBA mammary tumorigenesis in entire rats when hormone injections are begun just before or after carcinogen administration (Jabara, 1967;Jabara and Harcourt, 1970). By contrast, ovariectomy performed 7 days before feeding DMBA totally inhibits mammary tumour development (Jabara and Harcourt, 1970) whereas adrenalectomy has no significant effect on tumorigenesis (Jabara and Harcourt, 1971). Reported effects of hypothyroidism on mammary tumour induction range from an enhancement of carcinogenesis Thomas, 1966, 1967;Davidson, Owen and Thomas, 1969)

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Section: Discussionsupporting

confidence: 90%

“…As has been observed previously in entire rats (Jabara and Harcourt, 1970), in Group 1 and 2 neoplasms arose equally on both sides and most tumours were in the anterior 3 pairs of glands.…”

Section: Locations and Types Of Tumnourssupporting

confidence: 87%