Elevated expression of the proapoptotic BCL-2 family member, BAK, in the human endometrium coincident with apoptosis during the secretory phase of the cycle.
OBJECTIVE
To characterize the distribution of BAK (BCL-2 homologous antagonist/killer) protein in the human endometrium relative to the occurrence of apoptosis.


METHODS
A prospective, controlled study.


METHODS
An academic hospital.


METHODS
Premenopausal women with histologically normal endometrium who were undergoing hysterectomy and curettage.


METHODS
Endometrial tissues were collected.


METHODS
Detection of BAK protein by immunohistochemical and immunoblot analyses, and of apoptosis by in situ DNA end-labeling.


RESULTS
BAK protein was detected in secretory endometrium and was confined to the glandular epithelial cells of the functionalis layer. Immunoreactive BAK was absent from most of the cells of the proliferative endometrium. By immunoblot analysis, we confirmed the immunohistochemical data by demonstrating that a 30-kD protein corresponding to BAK was elevated in lysates prepared from secretory, as compared with proliferative, endometrium. The elevated levels of BAK coincided with the onset of apoptosis in endometrial glandular epithelial cells during the secretory phase of the menstrual cycle.


CONCLUSIONS
BAK protein localizes to glandular epithelial cells on the verge of apoptosis in the human endometrium. Thus, BAK likely functions with other members of the BCL-2 family in the regulation of apoptosis in the human uterus.
Department of Obstetrics and Gynecology, Massachusetts General Hospital/Harvard Medical School, Boston 02114, USA.
X J
XJ
Tao
R A
RA
Sayegh
J L
JL
Tilly
K B
KB
Isaacson
D000328:Adult; D017209:Apoptosis / Q000502:physiology*; D004249:DNA Damage; D004717:Endometrium / Q000378:metabolism*; D005260:Female; D006801:Humans; D015151:Immunoblotting; D007150:Immunohistochemistry; D008565:Membrane Proteins / Q000096:biosynthesis*; D008597:Menstrual Cycle / Q000502:physiology*; D008875:Middle Aged; D011446:Prospective Studies; D050998:bcl-2 Homologous Antagonist-Killer Protein
C494772:BAK1 protein, human; D008565:Membrane Proteins; D050998:bcl-2 Homologous Antagonist-Killer Protein