Nitric oxide modulates placental prostanoid production from late pregnant non-insulin-dependent diabetic rat

Severe reproductive dysfunction has been described in non-insulin-dependent diabetes mellitus (NIDDM), correlated with high glucose levels in the plasma. We have characterized an abnormal prostanoid profile in tissues from NIDDM rats, and a tight correlation between nitric oxide (NO) levels and prostaglandin production. Likewise, we have determined that parturition is delayed in NIDDM rats compared to control animals. In order to characterize the events which precede delayed parturition in NIDDM rats, we evaluate (a) the arachidonic acid (AA) conversion in placental tissue obtained from control (day 21 and 22) and NIDDM (day 21, 22 and 23) late pregnant rats into prostaglandin E2 (PGE2) and F2alpha (PGF2alpha), thromboxane B2 (TXB2) and 6-keto-prostaglandin F1alpha (6-keto-PGF1alpha), and (b) NO synthase (NOS) activity in control and NIDDM late pregnant animals. Placental arachidonate conversion from control rats into different prostanoids, namely PGE2, PGF2alpha, and TXB2, is higher in day 22 than in day 21, and radioconversion from diabetic rats into PGE2, PGF22, TXB2 and 6-keto-PGF1alpha on day 23 is higher than in day 21 and 22. 6-keto-PGF1alpha is lower and TXB2 is higher in diabetic tissues than in control. Placental AA conversion of control diabetic tissues on the day of delivery is decreased by N(G) monomethyl-L-arginine (LNMMA) (600 mM), a well known NOS inhibitor, while prostanoid production remains unaltered on previous days. NOS activity is higher in control on day 22 when compared to day 21, and in diabetic on day 23 when compared to day 22 of pregnancy. We conclude that elevated NO placental levels are observed in control (day 22) and NIDDM (day 23) rats, and may increase placental prostaglandin production on the day of delivery.