The objective of this study was to determine the temporal and spatial expression patterns of genes encoding transporters, as well as selected secreted proteins that may be regulated by progesterone (P4) and/or the presence of the conceptus in the bovine endometrium. Estrus-synchronized beef heifers were randomly assigned to either: 1) pregnant, high P4; 2) pregnant, normal P4; 3) cyclic, high P4; or 4) cyclic, normal P4. Uteri were collected on days 5, 7, 13, and 16 of the estrous cycle or pregnancy. Localization of mRNAs for ANPEP, CTGF, LPL, LTF, and SLC5A1 in the uteri was determined by radioactive in situ hybridization, and expression quantified in the endometria by quantitative real-time PCR. ANPEP localized to luminal (LE) and superficial glandular (sGE) epithelia of all heifers on days 5 and 7 only. SLC5A1 mRNA was detected in the LE and sGE on days 13 and 16 in all heifers, and expression increased on day 16 in pregnant groups. CTGF localized weakly to the LE and GE on days 5 and 7 but increased on days 13 and 16 with an increase (P < 0.05) in CTGF expression in high P4 (day 7) and pregnant heifers (day 16). Both LPL and LTF localized to the GE only on days 5 and 7. In conclusion we have characterized the temporal expression pattern of these genes and modulation of their transcript abundance by P4 (CTGF, LPL) and/or the conceptus (CTGF, SLC5A1) likely modifies the uterine microenvironment, enhancing histotroph composition and contributing to advanced conceptus elongation.
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