In addition, both COX-1 and COX-2 were higher in polyps when compared to adjacent mucosa of Pirc rats. The results showed that COX-1 expression levels were much higher than that of COX-2 in all the tested tissues including the colonic epithelium of F344 (28-fold) and Pirc rats (20-fold), colonic polyps of Pirc rats (8-fold), and biopsy specimens of SCC patients (11– 17-fold). Results: A robust LC-MS method for quantification of COX-1 and COX-2 was developed and validated and then used to calculate their apparent turnover numbers. The COX-1 and COX-2 turnover numbers were subsequently calculated based on apparent formation rates of PGE 2. Methods: An LC-MS method was developed and validated, then used for quantifying the absolute amounts of COX-1 and COX-2 in recombinant human COX-1 and COX-2, lysates from different cells, tissue microsomes of rodents and humans, Pirc rat colonic polyps, and biopsy specimens from squamous cell carcinoma (SCC) patients. Objective: We aim to quantify the absolute protein expression of cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2) in various cells and tissues to determine the relative contribution of COX-1 and COX-2 to PGE 2 production. Li Li, 1 Rongjin Sun, 1 Joseph Zenga, 2 Heather Himburg, 3 Lu Wang, 1 Shengnan Duan, 1 Jingwen Liu, 1 Dinh Bui, 1 Zuoxu Xie, 1 Ting Du, 4 Lijun Xie, 1 Taijun Yin, 1 Stu Wong, 2 Song Gao, 4 Ming Hu 1ġDepartment of Pharmacological and Pharmaceutical Sciences, College of Pharmacy, University of Houston, Houston, TX, USA 2Department of Otolaryngology and Communication Sciences, Medical College of Wisconsin, Milwaukee, WI, USA 3Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, WI, USA 4Department of Pharmaceutical Science, College of Pharmacy and Health Sciences, Texas Southern University, Houston, TX, USAĬorrespondence: Ming Hu, Department of Pharmacological and Pharmaceutical Sciences, College of Pharmacy, University of Houston, Houston, TX, USA, Email Song Gao, Department of Pharmaceutical Science, College of Pharmacy and Health Sciences, Texas Southern University, Houston, TX, USA, Email
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