Abstract
The ductus arteriosus (DA), a fetal connection between the pulmonary artery and the aorta, plays an important role in in utero cardiovascular circulation. Prostaglandin E (PGE) plays a principal role in maintaining the patency of the DA. The DA displays the higher sensitivity to PGE than other vascular smooth muscles. PGE activates adenylyl cyclases (ACs) via the EP4 receptor, resulting in an increase in the intracellular cAMP in the DA. ACs consist of 9 isoforms that demonstrate distinct tissue distribution and function. However, characterization of ACs remain undetermined in the DA. We examined the expression of AC isoform mRNAs in the DA by semi-quantitative and quantitative RT-PCR. Pooled tissues of the DA were obtained from Wistar rat embryos at embryonic day19 and day21, and neonates on the day of birth. AC2, AC3, AC4, AC5, AC6, AC7, and AC9 were expressed in the DA, while AC1 and AC8 were not detected. The expression of AC2, AC4, and AC6 mRNAs in the DA were significantly higher than that in the aorta. In particular, AC2 was expressed to a strikingly higher degree in the DA at embryonic day21 and the day of birth (~ 30% increase) than in the adult aorta. The expression of AC3, AC5, and AC7 mRNAs in the DA were comparable with those in the aorta. The present study identified multiple AC isoforms in the rat DA. AC2, AC4 and AC6 isoforms, in particular AC2, may play an important role in mediating PGE signal in the DA. [Jpn J Physiol 54 Suppl:S94 (2004)]
