The direct effect of levobupivacaine in isolated rat aorta involves lipoxygenase pathway activation and endothelial nitric oxide release.
BACKGROUND
Levobupivacaine is a long-acting local anesthetic with a clinical profile similar to that of racemic bupivacaine but with a greater margin of safety. Levobupivacaine produces dose-dependent vasoconstriction in vivo. Our goal in this in vitro study was to investigate the role of pathways involved in arachidonic acid metabolism in the levobupivacaine-induced contraction of isolated rat aorta and to determine which endothelium-derived vasodilators are involved in the modulation of levobupivacaine-induced contraction.


METHODS
Rat thoracic aortic rings were isolated and suspended for isometric tension recording. Cumulative levobupivacaine dose-response curves over a range of 10(-6) to 3 x 10(-4) M were constructed in 1) aortic rings with no drug pretreatment; 2) endothelium-denuded rings pretreated with quinacrine dihydrochloride (nonspecific phospholipase A(2) inhibitor: 2 x 10(-5), 4 x 10(-5) M), nordihydroguaiaretic acid (NDGA) (lipoxygenase inhibitor: 10(-5), 3 x 10(-5) M), indomethacin (nonspecific cyclooxygenase inhibitor: 10(-5) M), AA-861 (5-lipoxygenase inhibitor: 10(-5), 5 x 10(-5) M), fluconazole (cytochrome P450 epoxygenase inhibitor: 10(-5) M), verapamil (10(-5) M), or calcium-free solution; and 3) endothelium-intact rings pretreated with N(omega)-nitro-L-arginine methyl ester (L-NAME) (nitric oxide synthase inhibitor: 5 x 10(-5) M), indomethacin, or fluconazole. Levobupivacaine-induced contractile response at each concentration (10(-4), 3 x 10(-4) M) was assessed in endothelium-denuded rings. Dose-response curves for potassium chloride in endothelium-denuded rings were generated in the presence or absence of NDGA and AA-861. Intracellular Ca(2+) levels were monitored by Ca(2+) image analysis using Fluo-4 fluorescence in vascular smooth muscle cells treated with levobupivacaine alone or AA-861 plus levobupivacaine.


RESULTS
Levobupivacaine produced a tonic contraction in isolated rat aorta rings; this response was maximal at 10(-4) M levobupivacaine and gradually attenuated at 3 x 10(-4) M levobupivacaine. Levobupivacaine-induced contractions of endothelium-denuded rings were larger than those of endothelium-intact rings. Levobupivacaine-induced contraction of endothelium-denuded rings was attenuated by quinacrine dihydrochloride, NDGA, AA-861, verapamil, and calcium-free solution and, to a lesser extent, by indomethacin. L-NAME enhanced levobupivacaine-induced contraction of endothelium-intact rings and indomethacin slightly attenuated this contraction. NDGA and AA-861 attenuated the potassium chloride-induced contraction. AA-861 attenuated the levobupivacaine-induced intracellular calcium increase in vascular smooth muscle cells.


CONCLUSIONS
Our data indicate that levobupivacaine-induced contraction of rat aortic smooth muscle is mediated mainly by activation of the lipoxygenase pathway and in part by activation of the cyclooxygenase pathway. In addition, activation of the lipoxygenase pathway seems to facilitate calcium influx via L-type calcium channels. Endothelial nitric oxide attenuates levobupivacaine-induced contraction.
Choi
Yun Suk
YS
Department of Anesthesiology and Pain Medicine, Gyeongsang National University Hospital, Jinju 660-702, Republic of Korea. jtsohn@nongae.gsnu.ac.k.
Jeong
Young Seok
YS
Ok
Seong-Ho
SH
Shin
Il-Woo
IW
Lee
Seung Hwa
SH
Park
Jae-Yong
JY
Hwang
Eun Mi
EM
Hah
Young-Sool
YS
Sohn
Ju-Tae
JT
D000779:Anesthetics, Local / Q000494:pharmacology*; D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D016227:Benzoquinones / Q000494:pharmacology; D002045:Bupivacaine / Q000031:analogs & derivatives / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000502:physiology; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D066298:In Vitro Techniques; D000077554:Levobupivacaine; D008084:Lipoxygenase / Q000378:metabolism*; D016859:Lipoxygenase Inhibitors / Q000494:pharmacology; D008297:Male; D009637:Masoprocol / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism*; D011189:Potassium Chloride / Q000494:pharmacology; D011796:Quinacrine / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D014700:Verapamil / Q000494:pharmacology
D000779:Anesthetics, Local; D016227:Benzoquinones; D004791:Enzyme Inhibitors; D016859:Lipoxygenase Inhibitors; D009569:Nitric Oxide; D011189:Potassium Chloride; D009637:Masoprocol; C036837:2,3,5-trimethyl-6-(12-hydroxy-5,10-dodecadiynyl)-1,4-benzoquinone; D000077554:Levobupivacaine; D014700:Verapamil; D008084:Lipoxygenase; D011796:Quinacrine; D002118:Calcium; D002045:Bupivacaine