Inhibitory effect of D1-like and D3dopamine receptors on norepinephrine-induced proliferation in vascular smooth muscle cells

Abstract

The sympathetic nervous system plays an important role in the regulation of blood pressure. There is increasing evidence for positive and negative interactions between dopamine and adrenergic receptors; the activation of the α-adrenergic receptor induces vasoconstriction, whereas the activation of dopamine receptor induces vasorelaxation. We hypothesize that the D1-like receptor and/or D3receptor also inhibit α1-adrenergic receptor-mediated proliferation in vascular smooth muscle cells (VSMCs). In this study, VSMC proliferation was determined by measuring [3H]thymidine incorporation, cell number, and uptake of 3-(4,5-dimethylthiazol-2-yl)-diphenyltetrazolium bromide (MTT). Norepinephrine increased VSMC number and MTT uptake, as well as [3H]thymidine incorporation via the α1-adrenergic receptor in aortic VSMCs from Sprague-Dawley rats. The proliferative effects of norepinephrine were attenuated by the activation of D1-like receptors or D3receptors, although a D1-like receptor agonist, fenoldopam, and a D3receptor agonist, PD-128907, by themselves, at low concentrations, had no effect on VSMC proliferation. Simultaneous stimulation of both D1-like and D3receptors had an additive inhibitory effect. The inhibitory effect of D3receptor was via protein kinase A, whereas the D1-like receptor effect was via protein kinase C-ζ. The interaction between α1-adrenergic and dopamine receptors, especially D1-like and D3receptors in VSMCs, could be involved in the pathogenesis of hypertension.