Prostaglandin (PG) is a general name for compounds that have the prostanoic acid structure. In the organism, most PGs are synthesized by a series of reactions carried out by cyclooxygenase (COX) and PG synthases. There are five well-studied PGs: PGE2, PGF2α, PGI2, PGD2 and thromboxane B2 (TXB2) collectively known as principal lipid mediators, possessing both physiological and pathophysiological functions;