Endothelin A receptor is necessary for O₂constriction but not closure of ductus arteriosus

Abstract

In vitro and in vivo techniques were developed with genetically modified mice to determine whether endothelin-1 (ET-1) functions as an O(2) mediator in closure of the ductus arteriosus (DA) at birth. Wild-type CD-1 and 129/SvEv mice with ET(A) receptor -/-, +/-, and +/+ genotypes were used. Isolated DA from term ET(A) +/+ fetuses contracted to O(2) (5-95%) and a thromboxane A(2) analog (ONO-11113, 0.1 microM). Instead, ET-1 elicited a dual response with weak relaxation (0.1 nM) preceding contraction (1-100 nM). Indomethacin (2.8 microM) was also a constrictor. ET(A) -/- DA, unlike ET(A) +/+ DA, contracted marginally to O(2) and ET-1 but responded to ONO-11113. O(2) contraction was also reduced in ET(A) +/- DA. In vivo, DA constricted equally in tracheotomized ET(A) -/- and ET(A) +/+ newborns. Conversely, no DA constriction was seen in hyperoxic ET(A) -/- fetuses in utero, although it occurred in ET(A) +/+ and +/- littermates. We conclude that ET-1 mediates the DA constrictor response to O(2). Without ET-1, however, the vessel still closes postnatally, conceivably caused by the withdrawal of relaxing influence(s).

Oxygen Activates the Rho/Rho-Kinase Pathway and Induces RhoB and ROCK-1 Expression in Human and Rabbit Ductus Arteriosus by Increasing Mitochondria-Derived Reactive Oxygen Species

“…The temporal sequence of O 2 constriction of human (and rabbit) DA involves an early electrical phase (Kv channel inhibition, membrane depolarization, and activation of the L-type, voltage-gated calcium channel), 4,8,10 followed by a mediator phase (increased endothelin synthesis), 5,26 and finally, as this work shows for the first time, a calciumsensitization phase (activation of Rho-kinase; Figure 8). The electrical phase begins within 5 to 10 minutes of rising PO 2 ( Figures 1A, 1B, and 2A and Data Supplement Figure IIA), and the constriction is largely dependent on extracellular calcium ( Figure 3A and 3B).…”

Role of Store-Operated Calcium Channels and Calcium Sensitization in Normoxic Contraction of the Ductus Arteriosus

“…In the uterus, dilator prostaglandins are thought to play a role in keeping the ductus open, and after birth, endothelin helps to cause contraction. [17][18][19][20][21] However, normoxic contraction of the human ductus can be demonstrated in the presence of prostaglandin and nitric oxide synthesis inhibitors and endothelin blockers, 5 suggesting that these vasoactive substances are not essential for the onset of normoxic contraction. Although normoxic contraction is caused in part by the inhibition of K ϩ channels, membrane depolarization, and entry of calcium through L-type calcium channels, 6,7,22 the present studies show a significant normoxic contraction in the presence of the K v blocker 4-AP and the K Ca blocker TEA, indicating that another mechanism may be involved.…”

Role of Microsomal Prostaglandin E Synthase-1 (mPGES1)-Derived PGE2 in Patency of the Ductus Arteriosus in the Mouse

“…Body weight varied between 0.9 and 1.4 g, and only one fetus was used in each experiment. The procedure for dissection of the ductus arteriosus, normalization of internal circumference and mechanical record has been described previously (19). In brief, the animal was secured with its left side up in a dissection chamber containing ice-cold Krebs solution gassed with 5% CO 2 in N 2 .…”

“…Changes in ductus caliber through the transition from the pre to the postnatal condition were assessed by fixing the vessel in situ with the whole-body freezing technique (19,20). Briefly, animals were placed with their right side up in a Petri dish and were covered with an embedding medium (Tissue-Tek optimum cutting temperature compound; Sakura Finetek, Torrance, CA).…”