Mechanical properties of mesenteric resistance arteries from Dahl salt-resistant and salt-sensitive rats: Role of endothelin-1

Objective Hypertension has been associated with altered structure and mecha nics of resistance arteries. This study assessed whether the passive mechan ics of mesenteric small arteries are altered in hypertensive Dahl salt-sens itive rats (Dahl-SS) vs normotensive Dahl salt-resistant rats (Dahl-SR). Th e role of endothelin-1 in determining small artery mechanics was also studi ed. Design Male Dahl-SR and Dahl-SS were treated with high sodium (4% NaCl) for 10 weeks. Subgroups of each strain were treated with the ETA-endothelin re ceptor antagonist, A-127722 (30 mg/kg/d), concomitantly. Third-order branch es of mesenteric arteries were mounted in a pressure myograph and exposed t o intraluminal pressures ranging up to 140 mmHg, Media thickness and lumen diameter were measured at each pressure, from which wall mechanics were cal culated. Results Tail-cuff systolic blood pressure was elevated with high sodium in Dahl-SS vs Dahl-SR, At the given dose, A-127722 decreased blood pressure in Dahl-SS slightly but significantly. Lumen diameter was lesser end media-lu men ratios were greater in vessels from Dahl-SS. Under isobaric conditions, vessels from Dahl-SS exhibited decreased wall stress and incremental elast ic modulus, However, there were no changes in isobaric incremental distensi bility or elastic modulus in relation to wall stress. A-127722 attenuated t he changes in media:lumen ratio and isobaric stress observed in Dahl-SS. Conclusions Dahl salt-sensitive hypertension was associated with altered st ructure of mesenteric resistance arteries, which decreased wall stress. End othelin-l may be involved in these changes. These arteries exhibit decrease d isobaric stiffness end no difference in geometry-independent stiffness, i ndicating that the decreased lumen diameter is a result of eutrophic remode ling. J Hypertens 1998, 16:1907-1912 (C) 1998 Lippincott Williams & Wilkins .