lysis was performed for selected genes which have not been studied previously in the human endometrium across the menstrual cycle. These included AKR1C3, CBR1, AKR1B1, PTGDR and PTGER1. The analysis aimed to determine whether the RNA transcripts MedChemExpress Butein detected by Q-RT PCR were translated into protein products and to determine their spatial and temporal expression across the menstrual cycle. All transcripts detected by RT PCR were shown to be translated into protein products. The staining intensity of the immunohistochemistry suggested protein expression was comparable to RNA expression obtained by Q-RTPCR except for staining of AKR1C3 and AKR1B1 in the midsecretory phase and PTGER1 in the proliferative phase. These differences suggested a modest decrease in protein expression compared with the RNA expression profile, although caution must be exercised when interpreting immunohistochemistry. Quantitatively interpreting immunostaining between a section with intense localized staining and a section with moderate staining intensity throughout may give a misleading impression of differences in global expression levels. Continued Expression profiles of the prostanoid system in the endometrium 187 PCR from endometrial samples taken from the menstrual, proliferative, early secretory, mid-secretory and late secretory phase of the menstrual cycle. Expression levels were measured compared with a calibrator RNA sample. The graphs show individual values for each sample, mean expression levels in arbitrary units normalized to 18S ribosomal RNA and error bars represent SEM. Mn, P, ES, MS and LS; Different letters represent statistically significant differences between groups; ns, not significant. AKR1C3 immunostaining was localized to the glandular and luminal epithelium and the blood vessels. Immunostaining was very prominent throughout the cycle, and in the menstrual phase staining in the blood vessels became more prominent. CBR1 immunostaining was localized predominantly to the glandular and luminal epithelium. Staining was observed in the stroma throughout the menstrual cycle but was faint and inconsistent. AKR1B1 immunostaining was localized predominantly to PubMed ID:http://www.ncbi.nlm.nih.gov/pubmed/19816210 the glandular and luminal epithelium and the blood vessels with less intense and scattered stromal perinuclear staining. In the late secretory phase and 
menstrual phase immunostaining was observed in a subset of stromal cells. PTGDR immunostaining was localized to the glandular epithelium, blood vessels and throughout the stroma but not to all cells. Intense immunostaining was observed in aggregating cells in the stroma in the secretory phase and menstrual phase. PTGER1 was shown to be localized to the glandular epithelium. Immunostaining of proliferative phase and early secretory phase endometrium was weak and confined to the nuclear region. In the mid- and late secretory phases immunostaining was intense and localized predominantly to the apical membrane of the glandular epithelium. Menstrual phase immunostaining was faint and localized to the nuclear region of the glandular epithelium. Discussion Inflammatory events have been described in the human endometrium during the period of endometrial receptivity and menstruation. These events are characterized by an increase in endometrial capillary dilation, permeability, stromal edema, blood flow, leucocyte number and secretion of pro-inflammatory factors. Pro-inflammatory enzymes PTGS1 and PTGS2 are key mediators of these inflammatory processes. Howe