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Background: Cyclooxygenase isoforms (COX-1, COX-2) may exert differential regulatory actions on enteric motor functions under normal or pathological conditions. Aims: To examine the occurrence and functions of COX-1 and COX-2 in the neuromuscular compartment of normal distal colon using human and murine tissue. Methods: Gene expression (human, mouse), protein expression (human), gene deletion (mouse), and the effects of dual and isoform specific COX inhibitors on in vitro motility (human, mouse) were investigated. Results: Reverse transcription-polymerase chain reaction (RT-PCR) showed mRNA expression of COX-1 and COX-2 in human and wild-type mouse colonic muscle whereas only COX-2 or COX-1 was detected in COX-1 or COX-2 knockout animals. Immunohistochemistry localised both isoforms in neurones of myenteric ganglia, COX-1 in circular layer myocytes, and COX-2 in longitudinal muscle. Indomethacin (COX-1/COX-2 inhibitor), SC-560 (COX-1 inhibitor), or DFU (COX-2 inhibitor) enhanced atropine sensitive electrically induced contractions of human longitudinal muscle. The most prominent actions were recorded with indomethacin or SC-560 plus DFU. These results were confirmed under pharmacological blockade of non-cholinergic nerves. Atropine sensitive contractions evoked by carbachol in the presence of tetrodotoxin were enhanced by indomethacin or DFU but not by SC-560. In wild-type mice, contractile responses to electrical stimulation were enhanced by indomethacin, SC-560, or DFU. SC-560 potentiated electrically induced contractions in COX-2, but not COX-1, knockout mice. In contrast, DFU enhanced the contractions elicited by electrical stimuli in COX-1, but not in COX-2, knockout mice. Conclusions: These results indicate that COX-1 and COX-2 are expressed in the neuromuscular compartment of normal human colon where they modulate cholinergic excitatory control of colonic motility at prejunctional and postjunctional sites, respectively.

Ductus arteriosus (DA) closure is initiated by oxygen rise postnatally and progresses in two, functional-to-permanent, stages. Here, using GeneChip Arrays in rats (normoxic and hyperoxic fetus, normoxic newborn), we examined whether oxygen alone duplicates the birth process in affecting DA genes. In addition, by comparing DA with aorta (Ao), we identified features in postnatal gene profile marking transitional adjustments in a closing (DA) vs. a persistent (Ao) vessel. We found changes in neonatal DA denoting enhanced formation and action of the constrictor endothelin-1 (ET-1). Likewise, ANG II type 1 receptor was upregulated, and the compound was a constrictor. Conversely, relaxant PGE2 became less effective. Among agents for functional closure, only ET-1 was affected similarly by oxygen and birth. Coincidentally, neonatal DA showed enhanced contractile drive with upregulation of Rho-Rho kinase and calcium signaling along with downregulation of contractile proteins. The latter effect was shared by oxygen. Changes denoting active remodeling were also seen in neonatal but not hyperoxic fetal DA. Ao, unlike DA, exhibited postnatal variations in noradrenergic, purinergic, and PGI2 systems with opposing effects on vasomotion. Contraction and remodeling processes were also less affected by birth, whereas lipid and glucose metabolism were upregulated. We conclude that several agents, including ANG II as novel effector, promote functional closure of DA, but only ET-1 is causally coupled with oxygen. Oxygen has no role in processes for permanent closure. Functional closure is associated with downregulation of contractile apparatus, and this may render neonatal DA less amenable to tone manipulation. Conceivably, activation of metabolism in neonatal Ao is a distinguishing feature for transitional adaptations in the permanent vasculature.

1 Prenatal patency of the ductus arteriosus is maintained by prostaglandin (PG) E 2 , conceivably in concert with nitric oxide (NO). Local PGE 2 formation is sustained by cyclooxygenase-1 (COX1) and cyclooxygenase-2 (COX2), a possible exception being the mouse in which COX1, or both COXs, are reportedly absent. Here, we have examined the occurrence of functional COX isoforms in the nearterm mouse ductus and the possibility of COX deletion causing NO upregulation. 2 COX1 and COX2 were detected in smooth muscle cells by immunogold electronmicroscopy, both being located primarily in the perinuclear region. Cytosolic and microsomal PGE synthases (cPGES and mPGES) were also found, but they occurred diffusely across the cytosol. COX1 and, far more frequently, COX2 were colocalised with mPGES, while neither COX appeared to be colocalized with cPGES. 3 The isolated ductus from wild-type and COX1À/À mice contracted promptly to indomethacin (2.8 mm). Conversely, the contraction of COX2À/À ductus to the same inhibitor started only after a delay and was slower. 4 N G -nitro-l-arginine methyl ester (l-NAME, 100 mm) weakly contracted the isolated wild-type ductus. Its effect, however, increased three-to four-fold after deleting either COX, hence equalling that of indomethacin. 5 In vivo, the ductus was patent in all mice foetuses, whether wild-type or COX-deleted. Likewise, no genotype-related difference was noted in its postnatal closure. 6 We conclude that the mouse ductus has a complete system for PGE 2 synthesis comprising both COX1 and COX2. The two enzymes respond differently to indomethacin but, nevertheless, deletion of either one results in NO upregulation. PGE 2 and NO can function synergistically in keeping the ductus patent.