Primary Mammary Cells Research Articles

Differences in mediated mutagenesis and polycyclic aromatic hydrocarbon metabolism in mammary cells from pregnant and virgin rats.

The physiological state of pregnancy confers significant resistance to polycyclic aromatic hydrocarbon (PAH)-induced mammary tumorigenesis. We have tested the abilities of primary mammary cells from pregnant and virgin rats cultured on collagen-coated plates to metabolize PAHs and convert these carcinogens to mutagenic derivatives. Using a cell-mediated mutagenesis assay, we found that mammary epithelial cells from pregnant rats produced half the levels of mutagenic 7,12-dimethylbenz[a]anthracene (DMBA) metabolites formed by cells from virgin rats. Pregnant-derived mammary cells also showed consistently lower levels of metabolism of DMBA and benzo[a]pyrene (B[a]P) than cells from virgin rats. H.p.l.c. analysis of B[a]P metabolism by these cell populations indicated no significant qualitative differences in the extracellular and intracellular metabolites formed. We have previously shown that mammary cells from rat strains exhibiting significant differences in susceptibility to PAH-induced tumors have equivalent qualitative and quantitative abilities to metabolize PAH carcinogens. Our current data suggest that modifications in mammary tumor susceptibility found in various physiological states, unlike genetically determined differences, may be related in part to an altered ability to activate chemical carcinogens within the mammary gland.

Xanthine oxidase, an indicator of secretory differentiation in mammary cells

Elevated levels of xanthine oxidase were found in (1) lactating mouse mammary glands, compared with virgin and midpregnant glands; and (2) primary mouse mammary cells cultured on floating collagen gels, compared with non-secretory cells on attached gels. In primary culture, increase in xanthine oxidase activity above a basal level coincided with secretory activity as measured by casein production; intracellular levels of casein and xanthine oxidase showed a high degree of correspondence. It is suggested that xanthine oxidase levels can be used as an indicator of in vivo and in vitro secretory differentiation in mammary epithelial cells.

Failure to induce protection against transplanted mammary tumours by vaccination with the purified murine mammary tumour virus structural proteins GP52 and P28

Twelve-week-old female DBAf, ( BALB c × DBAf )F1 (CD 2) and GR mice were injected s.c. with the purified mouse mammary tumour virus (MTV)-derived proteins gp 52 and p 28 with adjuvant. Twenty days postvaccination, the DBAf mice were challenged i.p. with the MTV-containing L 1210 leukaemia; the vaccinated CD 2 and GR mice were challenged s.c. with solid primary mammary tumour cells. The vaccinated mice showed no delay in tumour appearance as compared to control animals which were treated with the adjuvant alone. With the leukocyte adherence inhibition assay performed on day 20 postvaccination, it was found that gp 52 induced good cellular reactivity; however, factors that block cellular reactivity were also demonstrated in the serum. Antibody titers as determined by an enzyme linked immuno assay were low or negative. MTV disrupted by freezing and thawing provided slight protection in DBAf mice against the growth of the L 1210 leukaemia. It is concluded that the immunogenic properties of gp 52 are too weak to provide a useful vaccine against transplanted mammary tumours.