Molecular characterization of alpha(1)-adrenoceptor gene family and its role in salt-induced high blood pressure in rainbow trout (Oncorhynchus mykiss)

alpha1-Adrenoceptors (alpha1-ARs) are members of the G-protein coupled receptor superfamily of membrane proteins that mediate the actions of the endogenous catecholamines, adrenaline and noradrenaline. alpha 1-ARs are the prime mediators of vascular smooth muscle contraction and hypertrophic growth, and play a key role in the regulation of arterial blood pressure. Four weeks of high-salt diet (11% NaCl) significantly increased blood pressure (37.1%). An average two-fold decrease in alpha1D-AR mRNA expression was observed in the DA, ABA and EBA in high-salt diet fed trout. The chronically hypertensive fish exhibited a blunted vascular response to hypercapnia and exogenous catecholamines. These results suggest either a lowered vascular response capacity or that alpha1D-AR down-regulation occurred in high-salt diet fed fish as a consequence of the elevated blood pressure. The alpha1D-AR is, at least in part, involved in salt-induced high blood pressure in rainbow trout. This study is the first to characterize the alpha1-AR gene family at molecular level in any fish species, and provides the first evidence for a link between alpha1-ARs and salt-induced high blood pressure