Mechanisms for perivascular adipose tissue-mediated potentiation of vascular contraction to perivascular neuronal stimulation: the role of adipocyte-derived angiotensin II.

In rat mesenteric arteries we have recently found that perivascular adipose tissue (PVAT) promoted vasoconstriction to perivascular neuronal activation (by electrical field stimulation, EFS) through generation of superoxide. In this study, we examined the role of adipocyte-generated angiotensin II in PVAT-mediated potentiation of contraction to nerve stimulation. In rat mesenteric PVAT, the presence of angiotesinogen and angiotensin I-converting enzyme (ACE) mRNA was confirmed by RT-PCR. Immunohistochemical staining showed the presence of angiotensin II in mesenteric PVAT. In rat mesenteric arteries, treatment of the vessels with an ACE inhibitor (enalaprilat) or angiotensin II type 1 receptor antagonist (candesartan) reduced PVAT-mediated potentiation of EFS-induced contraction. Exogenously applied angiotensin II enhanced EFS-induced contraction in arteries without PVAT, but not in the arteries with intact PVAT. Chronic treatment with an ACE inhibitor quinapril (14 days) lowered blood pressure and alleviated the potentiation effects of PVAT in EFS-induced contraction. Mesenteric arteries from quinapril-treated group now exhibited the potentiation response to exogenously applied angiotensin II in arteries with intact PVAT to a comparable level as in arteries with PVAT removed. Treatment with hydralazine reduced blood pressure to the same level as quinapril treatment, but did not affect PVAT-associated potentiation of vasoconstriction to EFS and the response to exogenously applied angiotensin II in PVAT-intact arteries. These results showed that adipocyte-derived angiotensin II is critically involved in PVAT-mediated potentiation of EFS-evoked contraction in rat mesenteric arteries.