LAUSR

HighlightsThe colon PGE2 of normal (wild type) rat and Pirc rat (an Apc‐mutant rat) were firstly accurately determined by specific and sensitive UPLC–MS/MS.PGE2 was confirmed to promote Pirc rat colon polyps.An optimized mobile phase (0.1% ammonia hydroxide) was found to greatly improve the chromatographic separation of prostaglandins. ABSTRACT An accurate and reliable UPLC–MS/MS method is reported for the quantification of endogenous Prostaglandin E2 (PGE2) in rat colonic mucosa and polyps. This method adopted the “surrogate analyte plus authentic bio‐matrix” approach, using two different stable isotopic labeled analogs — PGE2‐d9 as the surrogate analyte and PGE2‐d4 as the internal standard. A quantitative standard curve was constructed with the surrogate analyte in colonic mucosa homogenate, and the method was successfully validated with the authentic bio‐matrix. Concentrations of endogenous PGE2 in both normal and inflammatory tissue homogenates were back‐calculated based on the regression equation. Because of no endogenous interference on the surrogate analyte determination, the specificity was particularly good. By using authentic bio‐matrix for validation, the matrix effect and exaction recovery are identically same for the quantitative standard curve and actual samples – this notably increased the assay accuracy. The method is easy, fast, robust and reliable for colon PGE2 determination. This “surrogate analyte” approach was applied to measure the Pirc (an Apc‐mutant rat kindred that models human FAP) mucosa and polyps PGE2, one of the strong biomarkers of colorectal cancer. A similar concept could be applied to endogenous biomarkers in other tissues.