Modulation by epidermal growth factor--urogastrone of contraction in isolated canine helical mesenteric arterial strips.

We have examined the effect of epidermal growth factor--urogastrone (EGF-URO) on the response of isolated canine helical mesenteric arterial strips contracted by norepinephrine (NE), KCl, and transmural electrical stimulation (TES). Although EGF-URO alone did not affect resting arterial tone, contraction caused by all three modes of stimulation (NE, KCl, and TES) was inhibited up to 50% in the presence of EGF-URO. The action of EGF-URO did not depend on the presence of intact endothelial cells. The most pronounced effect of EGF-URO was observed on KCl-mediated contraction. The inhibitory effect of EGF-URO was maximal at about 15 min after addition of the polypeptide to the organ bath and persisted (e.g., electrical stimulation) for up to 1 h. A half-maximal inhibitory effect of EGF-URO was observed at a concentration of about 1 nM. Washing the tissue free of EGF-URO reversed its inhibitory action. Although in the presence of indomethacin (3 microM) EGF-URO caused a small, variable elevation in resting tension, the presence of indomethacin did not affect the ability of EGF--URO to inhibit contraction mediated by KCl. Under conditions wherein contraction in response to maximally effective concentrations of either NE or KCl was made dependent on the addition of calcium, EGF-URO was able to inhibit the response in the presence of KCl but not in the presence of NE.(ABSTRACT TRUNCATED AT 250 WORDS)