Document Detail

Cellular levels of O6-methylguanine-DNA methyltransferase in mammary epithelial cells and liver from virgin, pregnant and pituitary grafted mice.
MedLine Citation:
PMID:  1934259     Owner:  NLM     Status:  MEDLINE    
O6-Methylguanine-DNA methyltransferase (O6-MT) is a DNA repair protein that reverses alkylation damage at the O6 position of guanine. In the process, O6-MT undergoes suicide inactivation. To determine if this enzyme might be regulated by pregnancy-associated hormones we measured changes in the level of O6-MT in isolated mouse mammary epithelial cell homogenates during different reproductive states. These were pregnancy, ectopic pituitary transplantation, proestrus/estrus and diestrus. O6-MT levels were found to be similar in mice in proestrus/estrus (0.95 fmol/micrograms DNA) as compared to diestrus (0.94 fmol/micrograms DNA) and also mixed populations of virgin mice (1.09 fmol/micrograms DNA). A mean for all virgin mice (0.97 fmol/micrograms DNA) was used as a comparative index. O6-MT decreased 2-fold during pregnancy in mammary epithelial cells to a mean value of 0.45 fmol/micrograms DNA (P less than 0.05). A smaller decrease (0.65 fmol/micrograms DNA; P less than 0.01) in mammary epithelial cells was found at 3 weeks following pituitary isograft. The repair capacity of mammary epithelial cells to liver was compared by measurements made in liver homogenates from the same mice and are approximately 3-fold higher in liver from virgin mice (3.2 fmol/micrograms DNA) than mammary gland. Liver levels of O6-MT increased in pregnant (5.3 fmol/micrograms DNA) and pituitary transplanted (3.9 fmol/micrograms DNA) mice, and were 5- and 4-fold higher than the concentration in virgin mammary epithelial cells respectively.
T A Dutta-Choudhury; B H Bak; R C Guzman
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Carcinogenesis     Volume:  12     ISSN:  0143-3334     ISO Abbreviation:  Carcinogenesis     Publication Date:  1991 Oct 
Date Detail:
Created Date:  1991-11-25     Completed Date:  1991-11-25     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  8008055     Medline TA:  Carcinogenesis     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  1795-800     Citation Subset:  IM    
Department of Molecular and Cell Biology, University of California, Berkeley 94720.
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MeSH Terms
Colonic Neoplasms / enzymology,  pathology
Epithelial Cells
Epithelium / enzymology
Estrus / metabolism
Liver / cytology,  enzymology*
Mammary Glands, Animal / enzymology*
Methyltransferases / metabolism*
Mice, Inbred BALB C
O(6)-Methylguanine-DNA Methyltransferase
Pituitary Gland / physiology,  transplantation
Pregnancy, Animal / metabolism*
Tumor Cells, Cultured / enzymology
Grant Support
Reg. No./Substance:
EC 2.1.1.-/Methyltransferases; EC Methyltransferase

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