Placental thromboxane and prostacyclin production in an ovine diabetic model

We hypothesized that streptozocin-induced ovine diabetes would cause alterations in the placental production of thromboxane and prostacyclin. With a tissue incubation technique, we examined the placental production of thromboxane and prostacyclin in cotyledons from seven normal near-term ewes (127 ± 3 days' gestation) and six streptozocin-induced diabetic ewes (125 ± 3 days' gestation). Diabetic status was verified with serial fasting blood glucose assessments. Placental tissue was incubated in Dulbecco's modified Eagle's medium for 48 hours at 37° C with 95% oxygen and 5% carbon dioxide. Samples were collected at 0, 1, 2, 4, 8, 20, 32, and 48 hours. Radioimmunoassay of the stable metabolites thromboxane B₂ and 6-keto-prostaglandin F_1α were used to determine thromboxane and prostacyclin production, respectively. Placental thromboxane production was reduced in diabetic animals when compared with control animals (5.63 ± 2.81 vs 7.32 ± 1.37 pg/mg per hour, respectively; p < 0.05). Prostacyclin production was also significantly reduced in the diabetic placentas compared with control placentas (11.44 ± 4.06 vs 16.29 ± 4.59 pg/mg per hour, respectively; p < 0.05). We conclude that the ovine placenta produces thromboxane and prostacyclin. The ovine thromboxane production rate is comparable to that of the human placenta but the prostacyclin production rate is approximately two to three times higher. The observed decrease in the placental production of thromboxane and prostacyclin may reflect an adverse effect of hyperglycemia directly on eicosanoid production or indirectly through decreased placental cellular proliferation.