PRODUCTION OF PROSTAGLANDIN-F2-ALPHA AND E-2 IN EXPLANTS OF INTRAUTERINE TISSUES OF GUINEA-PIGS DURING LATE PREGNANCY AND LABOR

Prostaglandin production in amnion and decidua is considered important JOY human parturition. We investigated in pregnant guinea pigs, a spe cies similar to women in regard to the endocrinology of pregnancy whet her the production rates of PGE(2) and PGF(2 alpha) in various intraut erine tissues are compatible with a role in parturition. Net productio n rates were measured at 45, 55 and 65 days of gestation and during la bor in amnion, chorion, myo-endometrium, the outer. layer of the myome trium, the site of placental implantation, and placenta. Net productio n rates in amnion increased between 45 days and labor (30-fold for PGE (2) and 8-fold for PGF(2 alpha), P < 0.0001). During labor, the produc tion rates in amnion of PGE(2) (P = 0.006) and PGF(2 alpha) (P = 0.019 ) were higher than at 45, 55, and 65 days of gestation; In myo-endomet rium, the production rates of PGF(2 alpha) were higher at 65 days of g estation than at 55 days and during labor (P = 0.046). Addition of ara chidonic acid (10(-5) M) increased production of PGE(2) and/or PGF(2 a lpha) in all tissues (P < 0.05) except placenta. In amnion, the respon se to arachidonic acid increased with advancing gestation. This sugges ts that 1) PGE(2) and PGF(2 alpha) produced by amnion have a potential role in the initiation and maintenance of labor, 2) PGF(2 alpha) prod uced myo-endometrium has a potential role in the initiation of labor, 3) cyclooxygenase (s) are not rate-limiting except in placenta, and 4) the expression of cyclooxygenase in amnion increases with advancing g estation.