Role of β2- and β3-adrenoceptors in arterial stiffness in a state of hypertension
An increase in arterial stiffness is associated with a high risk for morbidity and mortality in a state of elevated systemic pressure. The sympathetic nervous system plays an important role in the regulation of vascular tone via activation of β-adrenoceptors. The aim of this investigation was to determine the involvement of β-adrenoceptors in the control of arterial stiffness in a state of hypertension versus normotension. Pulse wave velocity (PWV), an index of vascular stiffness, was assessed in isoflurane-anaesthetized 13–14-week-old male spontaneously hypertensive (SH) and Wistar-Kyoto (WKY) rats. At baseline, PWV was significantly higher in SH (9.2±0.9 m/s) compared to WKY rats (6.7±0.4 m/s). The stimulation of β2- but not β3-adrenoceptors significantly reduced PWV in SH rats despite comparable reductions in blood pressure. Stimulation of β2- or β3-adrenoceptors did not reduce PWV in WKY rats. The administration of sodium nitroprusside (SNP) also significantly reduced PWV in SH but not WKY rats. Immunofluorescence revealed the expression of β2- and β3-adrenoceptors in endothelial cells and vascular smooth muscle cells of the abdominal aorta. There were no significant differences in the distribution of the expression of β2- and β3-adrenoceptors in endothelial and/or smooth muscle cells in blood vessels of SH compared to WKY rats. The evidence suggests that β2-adrenoceptor stimulation and SNP infusion reduce PWV independently from reduction in blood pressure in a state of high systemic arterial pressure. A reduction in vascular tone of the central arteries may play a key role in decreasing PWV that is elevated due to stiffer arterial wall.