Abstract
Perivascular adipose tissue (PVAT) and its vasomodulatory effects play an important role in the physiology and pathophysiology of blood vessels. Alterations in PVAT associated with reduction in its anticontractile influence are proven to contribute to vascular dysfunction in hypertension. The aim of this study was to examine whether the changes in PVAT properties could participate in progression of vascular abnormalities in developing spontaneously hypertensive rats (SHR). Normotensive Wistar-Kyoto (WKY) rats and SHR, both in 5th and in 12th week of age, were used. Systolic blood pressure was similar between WKY rats and SHR in 5th week of age; however, in 12th week, it was significantly increased in SHR comparing to WKY rats. The amount of retroperitoneal fat was higher in WKY rats in both age groups, whereas body weight was higher in WKY rats only in 12th week, when compared to age-matched SHR. From isolated superior mesenteric arteries, two ring preparations were prepared for isometric tension recording, one with PVAT intact and other with PVAT removed. In WKY rats as well as in SHR, arterial contractile responses to noradrenaline, applied cumulatively on rings, were significantly inhibited in the presence of intact PVAT. In both age groups, anticontractile effect of PVAT was higher in WKY rats than in SHR. Neurogenic contractions, induced by electrical stimulation of perivascular sympathoadrenergic nerves, were significantly attenuated in the presence of PVAT in WKY mesenteric arteries from both age groups; however, in arteries from SHR, intact PVAT had no influence on this type of contractile responses. The results suggest that in SHR impairment of anticontractile effect of PVAT precedes hypertension and might contribute to its development.
Highlights
Perivascular adipose tissue (PVAT) has recently attracted high attention in cardiovascular research
Since the period of first experimental findings regarding the anticontractile effect of PVAT [1] and the potential existence of PVAT-derived relaxing factor(s) [2], many data have been gathered about biologically active substances of various chemical origin which are produced in PVAT and are capable of influencing vascular tone, physiological and pathophysiological growth of particular components of vessel wall, function of vascular autonomic nerves, cell migration, or inflammation processes [3,4,5]
In 5th week of age, spontaneously hypertensive rats (SHR) differed from WKY rats in higher heart rate and relative heart weight, as well as in lower amount of retroperitoneal fat
Summary
Perivascular adipose tissue (PVAT) has recently attracted high attention in cardiovascular research. One of the most studied effects of PVAT is its anticontractile influence which is probably mediated by several PVAT-derived factors; the most important seem to be angiotensin 1-7, methyl palmitate, hydrogen sulphide, nitric oxide, hydrogen peroxide, etc These substances act as hyperpolarizing factors which increase the membrane potential of vascular smooth muscle cells by activating different types of potassium channels, and this process leads to inhibition of vasoconstriction [4]. In pathological conditions associated with cardiovascular and metabolic dysfunction, adipocytes might be an important source of free radicals and proinflammatory cytokines [7].
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