Endothelin ETA receptor antagonism attenuates the presser effects of nicotine in rats

The increased endotheIin-1 levels observed after smoking may result from ni cotine-stimulated endothelin-1 production by endothelial cells. In this stu dy, we investigated the effects of selective endothelin ETA receptors antag onist Cycle D-a-aspartyl-L-prolyl-D-isoleucyl-D-tryptophyl (JKC 301) and of endothelin ETB receptors antagonist N-cis-2,6-dimethylpiperidino-carbonyl- L-gamma-methyl-leucyl-D-L-methoxycarbonyl-tryptophanyl-norleucine (BQ 788) on the changes in mean arterial pressure, heart rate, and plasma thromboxan e B-2 (the stable product of thromboxane A(2)) levels caused by increasing doses of nicotine (0.6, 2, 6, and 20 mu mol/kg) in anesthetised rats. Nicot ine (0.6, 2, and 6 mu mol/kg) significantly increased the mean arterial pre ssure in control and BQ 788-pretreated rats, while only a nicotine dose of 2 mu mol/kg) increased the mean arterial pressure in JKC 301-pretreated ani mals. There were no differences in the nicotine-induced changes in heart ra te or in the increases in thromboxane B-2 levels among the groups treated w ith saline, JKC 301 and BQ 788. These results demonstrate that whereas the antagonism of-endothelin ETA receptors attenuated the increase in blood pre ssure after nicotine injections, endothelin ETB receptor antagonism had no such effect. In addition, the antagonism of endothelin ETA or ETB receptors did not affect thromboxane A(2) production after nicotine administration. These findings suggest that endothelin-1 may have a role in the acute effec ts of nicotine. (C) 2000 Elsevier Science B.V. All rights reserved.