The contribution of gap junctions to endothelium‐dependent relaxation was investigated in isolated rabbit conduit artery preparations pre‐constricted by 10 μM phenylephrine (PhE). Acetylcholine (ACh) relaxed the thoracic aorta by ≈60 % and the superior mesenteric artery (SMA) by ≈90 %. A peptide possessing sequence homology with extracellular loop 2 of connexin 43 (Gap 27, 300 μM) inhibited relaxation by ≈40 % in both artery types. Gap 27 also attenuated the endothelium‐dependent component of the relaxation induced by ATP in thoracic aorta but did not modify force development in response to PhE. N G‐nitro‐L‐arginine methyl ester (L‐NAME, 300 μM), an inhibitor of NO synthase, attenuated ACh‐induced relaxation by ≈90 % in the aorta but only by ≈40 % in SMA (P < 0.05). Residual L‐NAME‐insensitive relaxations were almost abolished by 300 μM Gap 27 in aorta and inhibited in a concentration‐dependent fashion in SMA (≈50 % at 100 μM and ≈80 % at 10 mM). Gap 27 similarly attenuated the endothelium‐dependent component of L‐NAME‐insensitive relaxations to ATP in aorta. Responses to cyclopiazonic acid, which stimulates endothelium‐dependent relaxation through a receptor‐independent mechanism, were also attenuated by Gap 27, whereas this peptide exerted no effect on the NO‐mediated relaxation induced by sodium nitroprusside in preparations denuded of endothelium. ACh‐induced relaxation of ‘sandwich’ mounts of aorta or SMA were unaffected by Gap 27 but completely abolished by L‐NAME. We conclude that direct heterocellular communication between the endothelium and smooth muscle contributes to endothelium‐dependent relaxations evoked by both receptor‐dependent and ‐independent mechanisms. The inhibitory effects of Gap 27 peptide do not involve homocellular communication within the vessel wall or modulation of NO release or action.

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Its function has not been analyzed. Our goal was to determine the function of the MalX homologue by analyzing the phenotypes of mutants lacking the gene.METHODS: Using UTI89, a model UPEC strain, the malX homologue was deleted. The deletion strain was tested for growth on several sugars and swimming and surface motility with and without glucose.RESULTS: The malX homologue mutant had defective growth on glucose and xylose as carbon sources and lost both surface and swimming motility. A phylogenetic analysis suggests that the malX homologue is largely confined to the B2 phylogenetic group, which is the predominant group for UPEC.CONCLUSIONS: We propose that UPEC strains have a form of metabolism that is different from that of nonpathogenic E. coli strains, and that glucose transport is one aspect of metabolism that contributes to virulence.

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