Reiko Yanai

Inhibitory effects of potassium thiocyanate on normal and neoplastic mammary development in female mice

Abstract Effects of potassium thiocyanate (KSCN) on normal and neoplastic mammary development in female mice were studied. Administration of KSCN as drinking water (0.1 or 0.3%) for 12 weeks to 8-week-old SHN female mice resulted in the dose-related inhibition of development of normal mammary lobulo-alveolar system, hyperplastic alveolar nodules and spontaneous mammary tumors associated with marked decrease in plasma levels of triiodothyronine and thyroxine. On the other hand, the treatment affected little estrous cycles, ovarian structures, plasma prolactin levels and weights of body, anterior pituitary and adrenals. The incidence and number of pregnancy-dependent mammary tumors in GR/A female mice were also significantly suppressed by the similar treatment with KSCN with no influence on reproductivity as well as pituitary levels of prolactin and growth hormone. These results suggest that KSCN does not affect the secretion of pituitary and ovarian mammotropic hormones and that thyroid hormones are principally involved in normal and neoplastic development of mammary glands.

Quantitative Analysis of Prolactin by Disc Electrophoresis and Its Relation to Biological Activity

Summary The quantitative analysis of prolactin was investigated by disc electrophoresis. A linear relationship was found between the amount of standard prolactin preparation used and the optical density of the band obtained, indicating that this method can be employed for the quantitative determination of prolactin. One-2 mg of fresh pituitary from mature female rats was sufficient for clear detection of prolactin. A high correlation was obtained between the optical density and the biological activity of the eluate of the band. Chronic administration of large doses of prolactin to rats decreased the optical density of the prolactin band to 59% of that in the control pituitary. It was also demonstrated that prolactin released in vitro from the anterior pituitary of rats could be detected by disc electrophoresis.

Effects of progesterone on normal and prencoplastic mammary development in mice in relation to prolactin and estrogen

Abstract As a possible step to evaluate the role of progesterone in normal and neoplastic mammary development with special reference to its relation to prolactin and estrogen, the effects of alteration of circulating level of progesterone by prostaglandin (PGF 2 x or PGE 2 ) or an analogue of gonadotropin releasing hormone (TAP- 144 ) on precancerous mammary hyperplastic alveolar nodules (HAN) were studied in female mice. Plasma levels of prolactin and progesterone were assayed by radioimmunoassay and estrogen level was estimated by the uterine weight. Daily injections of PGE 2 ( 50 μg × 2 ) or TAP- 144 ( 10 μg ) for 20 days resulted in the increase in the rate of HAN formation associated with the elevation of circulating level of progesterone and no alteration of prolactin and estrogen. Furthermore, in ovariectomized, pituitary grafted mice given progesterone pellets and estrone as drinking water, the rate of HAN formation was found to depend upon progesterone level in the circulation. All observations indicate that elevated progesterone acts stimulatorily on HAN formation under no difference in the circulating levels of prolactin and estrogen.

Pituitary prolactin and growth hormone levels during different reproductive states in mice with a high or a low lactational performance

Abstract The pituitary prolactin and growth hormone (GH) levels were determined by disc electrophoresis on 10% polyacrylamide gel during the virginal and pregnant stages and on Day 12 of lactation, using C3H/He and C57BL/6 mice. The former had been shown to be superior to the latter in both mammary development and lactational performance. The pituitary prolactin levels were significantly higher in C3H/He mice than in C57BL/6 mice during the virginal and pregnant stages. However, no strain differences existed in the prolactin levels on Day 12 of lactation. Little difference in the prolactin levels was found between estrus and diestrus, and the levels declined gradually with the advance of pregnancy in both strains. The levels decreased after 1 hr of suckling preceded by 8-hr removal of young on Day 12 of lactation in both strains, but the difference between before and after suckling was statistically significant only in C3H/He mice. Both pituitary GH content and concentration were significantly higher in C3H/He mice than in C57BL/6 mice during the virginal stage and the content was also higher in C3H/He mice during the pregnant stage. However, there existed no strain difference in the levels on Day 12 of lactation. Little change in the pituitary GH levels was observed during the different reproductive states in both strains.

Effect of progesterone and estrogen on DNA synthesis of pregnancy-dependent mammary tumors in GR/A mice.

Abstract The effects of progesterone and estrogen on the growth and DNA synthesis of pregnancy dependent mammary tumors of GR A mice were studied. One group of mice with palpable mammary tumors received daily subcutaneous injections of 3mg progesterone plus 0.5μg estradiol benzoate in combination during days 14 and 19 of pregnancy and ovariectomized bilaterally on day 15. Another group of mice was given only the unilateral ovariectomy on day 15. These treatments resulted in the increase in mammary tumor size and the prevention of decrease in DNA synthesis (estimated by the in vivo incorporation of (3H) thymidine) of normal and neoplastic mammary glands on day 19 of pregnancy. On the other hand, mammary tumor size changed little and DNA synthesis of either gland was significantly decreased in ovariectomized mice receiving 2mg progesterone alone. Three mg progesterone increased DNA synthesis of mammary tumors, but not of normal glands as compared to 2mg progesterone. These results indicate that both progesterone and estrogen are essential for the growth of pregnancy-dependent mammary tumors and that there are some differences in responsiveness to progesterone between normal glands and pregnancy-dependent mammary tumors.

Relative importance of genotype and type of mammary tumor virus on mammary tumorigenesis in mice

Abstract Relative importance of genotype and type of mammary tumor virus (MTV) on determining the biological and morphological characteristics of mammary tumors appearing during reproductive states was studied in mice. Females of GR/A § , SHN, their reciprocal F1 hybrids [(GR × SHN)F1 and (SHN × GR)F1, GR/A fosternursed by SHN lactators (GR/SHN) and SHN fosternursed by GR/A lactators (SHN/fGR) were subjected to force breeding until the 3rd to the 5th pregnancy beginning 60 days of age. In GR/A, both F1-hybrids and GR/fSHN, mammary tumor incidence by the 3rd pregnancy was 88–100%, all tumors were pregnancy-dependent and almost all of them were diagnosed as plaques or mammary tumor type p. On the other hand, in SHN and SHN/fGR, mammary tumor incidence and percentage of pregnancy-dependent tumors were very low and most of the tumors were adenocarcinoma. Numbers of tumors per mouse were 2.2–3.2 and about 1 in the former four and in the latter two groups, respectively. Taking into consideration of the genotype(s) and type(s) of MTV of each group of mice, these results indicate that the relative importance as factors for determining the characteristics of mammary tumors during the reproductive states in mice is in the order of GR-genotype, SHN-genotype, GR type of MTV and SHN type of MTV.

The In Vitro mammary gland response to mammotropic hormones in mice with different mammary tumorigenesis

Abstract Mammary gland DNA synthesis estimated by the in vitro incorporation of [ 3 H]thymidine in response to mammotropic hormones was compared between high and low mammary tumor strains of virgin mice (SHN and SLN). In SHN, mammary gland DNA synthesis when cultured in the medium containing insulin (I), aldosterone (A), estradiol- 17 β (E), progesterone, prolactin (PRL) and growth hormone (GH) showed a peak on day 2 of culture and declined thereafter. Quite the opposite was the case in SLN mammary glands. There was little strain-difference in mammary gland DNA synthesis when cultured for 6 days in the medium containing complete hormone mixture. However, DNA synthesis of SHN mammary glands cultured in the medium deficient in PRL was less than one-third of the control, whereas that of SLN glands was two-thirds of the control. Moreover, mammary gland DNA synthesis was decreased significantly by deficiency in GH or E in SHN strain only. In both strains, mammary gland DNA synthesis declined with an increasing dose of PRL when cultured in the medium containing I, A and PRL, which was associated with an activated secretory function. However, the changes were much more marked in SHN than in SLN. The results have demonstrated the higher dependency of SHN mammary glands than SLN glands upon mammotropic hormones, especially PRL. They further indicate that mammary gland potential for both growth and function is well reflected by mammary gland sensitivity to PRL.

Inhibitory effect of Nocardia rubra cell wall skeleton on carcinogen-induced mammary tumorigenesis in rats

Abstract The inhibitory effects of the cell wall skeleton (CWS) of Nocardia rubra , a potent immunopotentiator, on carcinogen-induced mammary tumorigenesis and serum prolactin levels in rats were studied. Sprague-Dawley female rats were divided into four groups at 4 weeks of age; the first group served as the control and the second group received 150 μ g CWS of N. rubra every other week throughout the experiment. The third and the fourth groups were given CWS every other week only before and after the administration of 7,12 -dimethylbenz(a)anthracene (DMBA), respectively. CWS was injected intravenously (i.v.) for the first three injections and subcutaneously (s.c.) thereafter. All rats were given single i.v. injections of fat emulsion of 5 mg DMBA at 8 weeks of age. Both incidence and progression of mammary tumors were significantly inhibited in rats treated with CWS throughout the experiment and in rats given CWS only after DMBA administration. On the other hand, treatment with CWS only before DMBA injection had little effects. CWS of N. rubra reduced serum level of prolactin, an important hormone for mammary tumorigenesis.

Mammary tumour incidence in relation to the pattern of oestrous cycles in mice.

The patterns of oestrous cycles were examined in new strains of mice exhibiting a high (SHN) and a low (SLN) mammary tumour incidence. These mice originated from the same stock of Swiss albino mice. At the age of 3-4 months, SHN mice showed much longer cycles with continual dioestrous periods than SLN mice. The average lengths of cycles and dioestrous periods were, respectively, 8.3 +/- 0.3 and 6.0 +/- 0.4 days in SHN mice and 4.6 +/- 0.1 and 2.5 +/- 0.1 days in SLN mice. Furthermore, the distinct alteration in the patterns of cycles from SHN to SLN type was associated with complete reduction in mammary tumour incidence in highly inbred C3H/He female mice maintained by brother X sister mating with no selection for mammary tumourigenesis. The relation between the pattern of oestrous cycles and mammary tumourigenesis is discussed from the viewpoint of the endogenous hormonal milieu and the responsiveness of target organs.

Suppression of lactation by tumor promoters in mice.

Abstract As a possible step to evaluate the role of tumor promoters in normal cells, the effects of phorbol and its ester, 12-O-tetradecanoyl-phorbol-13-acetate (TPA), on normal mammary gland function and pituitary secretion of growth hormone (GH) and prolactin, were examined in lactating C3H/He mice. Daily subcutaneous injections of 400 μg phorbol or 4 μg TPA during Days 12 and 14 of lactation resulted in a significant decline in litter growth rate and the ratio of RNA synthesis: DNA synthesis of mammary glands associated with an increase in mammary gland DNA synthesis. On the other hand, pituitary synthesis and release of GH and prolactin, the pattern of estrous cycles and ovarian structures were affected little by these treatments. All findings strongly suggest that these tumor promoters can directly inhibit lactation by shifting mammary gland cells from a functional state to a mitotic state.