Expression of phosphodiesterase 5 in maternal and fetal sheep

Objective: Ovine pregnancy is associated with elevated levels of nitric oxide. Nitric oxide stimulates cyclic guanosine monophosphate (cGMP), which results in vascular smooth muscle relaxation/vasodilation. Phosphodiesterase type 5 regulates cGMP in the urogenital track. The present study was designed to determine message expression of phosphodiesterase type 5 in the myometrium, uterine vessels, and placentome of the sheep and phosphodiesterase type 5 protein expression in the maternal and fetal placentome. Study design: Tissue was collected from 5 nonpregnant and 5 pregnant anesthetized animals (gestational day = 134 +/- 4) and frozen at -80 degrees C. Optimized reverse transcription polymerase chain reaction was performed on all tissues, and immunohistochemistry was performed on the placentome only. Results: Phosphodiesterase type 5 messenger ribonucleic acid levels were significantly higher in the myometrium and placentome, compared with the maternal blood vessels. Phosphodiesterase type 5 protein was immunolocalized to the vascular smooth muscle of the maternal vessels, stroma, and placental capsule only. Conclusion: Although phosphodiesterase type 5 messenger ribonucleic acid was present in the fetal placenta, phosphodiesterase type 5 protein was expressed only in maternally derived placental tissue. This suggests that regulation of cGMP levels and vascular tone in the umbilical circulation differs from the uterine circulation. (C) 2005 Mosby, Inc. All rights reserved.