Role of β_2- 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±0.9m/s) compared to WKY rats (6.7±0.4m/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.

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