Differences in aortic response to vasoactive stimuli in Japanese and Lyon rats. The role of hypertension

Objective We have previously shown that conduit arteries of normotensive (W KY) and hypertensive (SHR) Japanese rats differ from normotensive (LN) and hypertensive (LH) Lyon rats in terms of lower aortic thickness and higher c ollagen III content, whereas differences in vasoactive properties are unkno wn. Methods Aortic rings with (E+) and without (E-) endothelium were studied un der resting and noradrenaline-stimulated conditions in the presence of N om ega-nitro-L-arginine (L-NNA) alone or in association with indomethacin, bos entan and/or BQ123. Results Under resting conditions, aortas of normotensive and hypertensive J apanese rats differed from Lyon rats by higher developed tension in the pre sence of L-NNA and endothelium. In the absence of endothelium, normotensive s differed from hypertensives in terms of stronger developed tensions in th e presence of L-NNA in the two strains. Addition of indomethacin to L-NNA i nduced relaxation in E+ SHR and E- WKY and contraction in ELH. By contrast, tensions were unchanged after addition of bosentan and BQ123. Under stimul ated conditions, tensions were equally increased by L-NNA in E+ and unchang ed in E- both in Japanese and Lyon rats whether they were normotensive or h ypertensive, and indomethacin (but not bosentan) elicited higher response i n Lyon than in Japanese rats in E+ and E- aorta. Conclusion Under NO synthase inhibition, the vasoactive properties of Japan ese and Lyon aorta differ in the presence of a cyclo-oxygenase blocker but not endothelin blockers. These results indicate that the aorta vasorelaxant tone is associated to prostanoid regulation in Lyon but not in Japanese ra ts. This observation appears dependent on the genetic and/or environmental background linked to the origin and not the presence of hypertension. J Hyp ertens 1999, 17:1403-1411 (C) Lippincott Williams & Wilkins.