ABSTRACT. Patients with chronic renal failure develop an autonomic dysfunction with impaired baroreflex control and attenuated cardiovascular β-adrenoceptor response to noradrenaline. In rats that underwent 5/6-nephrectomy (SNX), cardiac β-adrenoceptor responsiveness was reduced as well. Therefore, the aim of this study was to further investigate the mechanism underlying cardiac β-adrenoceptor desensitization in SNX rats. For this purpose, right and left ventricular β-adrenoceptor density, activity of the G-protein–coupled receptor kinase, and activity and density of the neuronal noradrenaline transporter (uptake1) were assessed in SNX rats. Seven weeks after SNX, rats had developed left heart hypertrophy. Plasma creatinine, urea, and noradrenaline levels were significantly increased; left and right ventricular noradrenaline content was significantly decreased when compared with sham-operated control rats. In these SNX rats, left, but not right, ventricular β-adrenoceptor density was significantly reduced, and membrane-associated G-protein–coupled receptor kinase activity was significantly increased compared with sham-operated rats. Although right and left ventricular activity of uptake1 was unchanged, the neuronal noradrenaline transporter density was significantly reduced in both ventricles of SNX versus sham-operated rats. An increase in left ventricular G-protein–coupled receptor kinase activity, possibly triggered by enhanced cardiac noradrenaline release, might be responsible for the decrease in left ventricular β-adrenoceptor responsiveness in SNX rats.
Concomitant Increase of G Protein-Coupled Receptor Kinase Activity and Uncoupling of β-Adrenergic Receptors in Rat Myometrium at Parturition
