Endothelin-1- and acetylcholine-mediated effects in human and rat vessels: impact of perivascular adipose tissue, diabetes, angiotensin II, and chemerin.

OBJECTIVE

To study the role of perivascular adipose tissue (PVAT) in the reactivity of rat and human vessels.

METHODS

Iliac and mesenteric arteries were obtained from normotensive Sprague-Dawley rats, hypertensive transgenic (mRen2)27 rats overexpressing mouse renin, and (mRen2)27 rats made diabetic with streptozotocin. Human coronary arteries were obtained from donors. Concentration-response curves were constructed to endothelin-1 and acetylcholine with and without PVAT. The contribution of NO and endothelium-dependent hyperpolarization (EDH) were determined making use of the NO synthase inhibitor L-NAME and the EDH inhibitors apamin + TRAM-34. The endothelin type A and type B (ET, ET) receptor blockers BQ123 and BQ788, the chemerin inhibitors α-NETA and pravastatin, and the angiotensin receptor blocker losartan were also used.

RESULTS

In rat iliac arteries, PVAT diminished endothelin-induced constriction, while the opposite was true in human coronaries. Coronary effects were unaltered by α-NETA, pravastatin, or losartan. ET receptor-mediated relaxation in iliac arteries occurred only with PVAT, and BQ123 blocked endothelin-1-induced constriction. Diabetes upregulated the anticontractile effects of PVAT. In rat mesenteric arteries, acetylcholine-induced relaxation with PVAT relied on NO, and on NO + EDH without PVAT. Diabetes upregulated the EDH component exclusively with PVAT.

CONCLUSION

PVAT modulates ET-1-induced constriction in a vessel type-dependent manner. Its enhancing effects in coronaries involved neither chemerin nor angiotensin II. Its anticontractile effects in rat iliac arteries involved ET receptor-mediated relaxation. Diabetes upregulated PVAT's anticontractile effects. In mesenteric arteries, PVAT counterbalanced the EDH component of the relaxant effect of acetylcholine. Diabetes reversed this effect by upregulating the EDH component.