Contractile responses of the human umbilical artery to KCl and serotonin in Ca-free medium and the effects of levcromakalim.
It is known that K(ATP) channel openers inhibit the release and refilling of Ca(2+) from intracellular stores. The present study was designed to test the effects of levcromakalim in human umbilical artery (HUA) rings stimulated by serotonin (5-HT) and KCl in Ca-free medium. Umbilical cords were obtained at vaginal or cesarean deliveries from healthy, term pregnancies. After the isolation, HUA rings were placed in organ baths in solution with indomethacin (10(-5) M) and N(G)-nitro-L-arginine methyl ester (L-NAME) (10(-3) M) at 37 degrees C and aerated with 95% O(2) and 5% CO(2) for the measurement of isometric force. In Ca-free solution with Ethylene glycol-bis (ss-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) (2 mM) the contractions produced by 5-HT (10(-6) M) and KCl (40 mM) decreased significantly. Afterwards, HUA rings were treated with 5-HT and KCl in repeated manner in Ca-free medium. In contrast to KCl, 5-HT induced contractions reduced in each application, progressively. Levcromakalim (10(-4) M) abolished the contractions elicited by 5-HT. On the other hand, levcromakalim had a little but significant inhibitory effect on KCl induced contraction in Ca-free medium. These results suggest that Ca(2+) is not the only transduction pathway in KCl produced contractions of HUA smooth muscle cells.
Tufan
Hale
H
Department of Pharmacology, School of Medicine, Başkent University, Bağlica Campus, Eskisehir Road, 20 km, 06530 Ankara, Turkey. htufan@baskent.edu.tr
Ayan-Polat
Belgin
B
Tecder-Unal
Müge
M
Polat
Gurur
G
Kayhan
Zeynep
Z
Oğüş
Ersin
E
D002118:Calcium / Q000008:administration & dosage*; D002614:Chelating Agents / Q000494:pharmacology; D019806:Cromakalim / Q000494:pharmacology*; D004533:Egtazic Acid / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D007213:Indomethacin / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000502:physiology; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D011189:Potassium Chloride / Q000494:pharmacology*; D012701:Serotonin / Q000494:pharmacology*; D012996:Solutions; D014469:Umbilical Arteries / Q000187:drug effects* / Q000502:physiology; D014665:Vasodilator Agents / Q000494:pharmacology*
D002614:Chelating Agents; D004791:Enzyme Inhibitors; D012996:Solutions; D014665:Vasodilator Agents; D019806:Cromakalim; D012701:Serotonin; D004533:Egtazic Acid; D011189:Potassium Chloride; D002118:Calcium; D019331:NG-Nitroarginine Methyl Ester; D007213:Indomethacin