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    In vitro vasoactive effects of dexmedetomidine on isolated human umbilical arteries
    (Comenius Univ, 2019) Arun, O.; Taylan, S. B.; Duman, I; Oc, B.; Yilmaz, S. A.; Tekin, A.; Celik, C.
    OBJECTIVE: We aimed to investigate the vasoactive effects of dexmedetomidine on isolated human umbilical arteries and possible mechanisms involved. METHODS: Human umbilical artery strips were suspended in Krebs-Henseleit solution and dose-response curves were obtained for cumulative dexmedetomidine before and after incubation with different agents; propranolol, atropine, yohimbine, prazosin, indomethacin, verapamil. Effects of calcium on cumulative dexmedetomidine-induced contractions were also studied. RESULTS: Cumulative dexmedetomidine resulted in dose dependent contraction responses. Incubation with propranolol (Emax: 93.3 +/- 3.26 %), atropine (Emax: 92.0 +/- 6.54 %), or indomethacin (Emax: 94.25 +/- 2.62 %), did not attenuate dexmedetomidine-elicited contractions (p > 0.05). There were significant decreases in the contraction responses of cumulative dexmedetomidine with yohimbine (Emax: 12.1 +/- 11.9 %), prazosin (Emax: 28.8 +/- 4.6 %) and verapamil (Emax: 11.2 +/- 13.6 %) (p < 0.05). In Ca+2 free medium contraction responses to cumulative dexmedetomidine was insignificant (Emax: 5.20 +/- 3.42 %). Addition of cumulative calcium to the Ca+2 free medium resulted in concentration dependent increase in contractions (Emax: 64.83 +/- 37.7 %) (p < 0.05). CONCLUSION: Dexmedetomidine induces vasoconstriction in endothelial-free umbilical arteries via both, alpha(1)- and alpha(2)-adrenergic receptors and also extracellular Ca+2 concentrations play a major role. beta-adrenergic receptors, muscarinic cholinergic receptors, and inhibition of cyclooxygenase enzyme are not involved in this vasoconstriction (Fig. 3, Ref. 36). Text in PDF www.elis.sk.