Expression of prostanoid receptors in human ductus arteriosus

Abstract

1. Prostaglandins play a major role in maintaining ductal patency in utero. Ductal tone is regulated by both locally released and circulating vasodilatory prostaglandins. In infants with ductus arteriosus-dependent congenital heart disease, ductal patency is maintained by intravenous administration of prostaglandin (PG) E(1). Little information is available regarding the expression of prostaglandin receptors in man. 2. By means of RT-PCR and immunohistochemistry we studied the expression of the PGI(2) receptor (IP), the four different PGE(2) receptors (EP1, EP2, EP3 and EP4), and the receptors for thromboxane (Tx) A(2) (TP), PGD(2) (DP) and PGF(2alpha) (FP) in the ductus arteriosus of three newborn infants with ductus arteriosus-dependent congenital heart disease and intravenous infusion of PGE(1) and of one 8 month old child with a patent ductus arteriosus. 3. The EP3, EP4, FP, IP and TP receptor were markedly expressed at the mRNA and protein level, whereas the EP2 receptor was weakly expressed and the EP1 receptor was detected in two out of four tissue specimens only. The DP receptor was not detected in any of the samples. The most pronounced expression, which was located in the media of the ductus arteriosus, was observed for the EP4 and TP receptors followed by IP and FP receptor protein. 4. These data indicate that ductal patency during the infusion of PGE(1) in infants with ductus arteriosus-dependent congenital heart disease might be mediated by the EP4 and IP receptor. The data further suggest that a heterogeneous population of prostanoid receptors may contribute to the regulation of ductus arteriosus tone in humans.

Figure 1

Expression of prostanoid receptor mRNA in human DA. RNA was isolated from excised tissue, reverse-transcribed by oligo(dT) and PCR amplification for all tissue samples was repeated three times. A fragment of β-actin was amplified as internal control. A representative expression pattern of one tissue sample is shown, base pair markers (bp) are indicated on both sides.

Figure 2

Expression of the different prostanoid receptors relative to the expression of β-actin. RNA was isolated from excised tissue, reverse-transcribed by oligo(dT) and PCR amplification was performed for the indicated prostanoid receptors. Intensity of DNA bands is presented as percentage of amplification of β-actin fragment.

Figure 3

Immunohistochemical localization of prostanoid receptors in human DA. Cryosections were prepared and incubated with anti prostanoid receptor antibodies. Antibody binding was visualized by APAAP technique (for all except EP4 receptor) or ABC technique (for EP4 receptor). The target receptors of the used antibodies are indicated below each figure. Control represents staining without primary antibody. A representative experiment staining is shown, exemplarily stained cells are indicated by arrows. Light microscope, ×200. Lu, lumen of ductus arteriosus.