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Proenkephalin A and the gamma-aminobutyric acid A receptor pi subunit: expression, localization, and dynamic changes in human secretory endometrium.

Quezada M, Henríquez S, Vargas M, Cardenas H, Tapia A, Rios M, Salvatierra AM, Orihuela PA, Croxatto HB, Velasquez L

Laboratorio de Inmunología de la Reproducción, Facultad de Química y Biología, Universidad de Santiago de Chile, Santiago, Chile.

OBJECTIVE: To compare mRNA and protein levels of proenkephalin A (PEA) and gamma-aminobutyric acid A receptor pi subunit (piGABA-R) in human secretory endometrium before and during receptivity and to determine the cell phenotypes where they are expressed. DESIGN: Prospective and observational, comparing prereceptive vs. receptive stages of secretory endometrium within the same nonconceptional menstrual cycle. SETTING: University and non-governmental organization (NGO)-based academic and clinical-research facilities. PATIENT(S): Seven healthy, multiparous, surgically sterilized women with spontaneous regular menstrual cycles. INTERVENTION(S): Endometrial biopsies were obtained on LH+3 and LH+7 within the same cycle. MAIN OUTCOME MEASURE(S): Levels of PEA and piGABA-R mRNA were determined by real-time PCR, and protein presence, by immunofluorescence. RESULT(S): The mRNA level of PEA fell, whereas that of piGABA-R increased, during endometrial receptivity. Positive immunostaining of PEA was found in the luminal and glandular epithelium, whereas that of piGABA-R was in luminal epithelium and stromal cells. CONCLUSION(S): The discrete cell-phenotype localization and timing of the changes in the level of PEA and of piGABA-R mRNA and protein suggest an important role for these molecules in switching the human endometrium from a refractory to a receptive state.

Published 27 November 2006 in Fertil Steril, 86(6): 1750-7.
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