Immunofluorescent imaging of beta(1)- and beta(2)-adrenergic receptors in rat kidney

Background. beta -Adrenergic receptors (beta -ARs) are known to participate in the regulation of glomerular filtration, NaCl reabsorption, acid-base b alance. and renin secretion, however. the precise histologic localization o f beta -AR at putative signaling sites involved in these processes remains an open issue. Methods. We used a set of subtype-specific rabbit antibodies to visualize b eta (1)- and beta (2)-AR in rat kidney by immunohistochemistry and specifie d cells and segments of the nephron thought to be regulated by catecholamin es. In addition. the relative proportion of beta -AR subtypes in cortical a nd medullary portions of rat kidney was determined by Western blotting and by competing [I-125]-cyanopindolol binding with the beta (1)- or beta (2)-s elective antagonists bisoprolol or ICI 118,551. respectively. Results. Immunoreactivity for beta (1)-AR was found in mesangial cells, jux taglomerular granular cells, the macula dense epithelium. proximal and dist al tubular segments, and acid-secreting type A intercalated cells of the co rtical and medullary collecting ducts. Immunoreactivity for beta (2)-AR was predominantly localized in the apical and subapical compartment of proxima l and. to a lesser extent, distal tubular epithelia (suggesting interaction s with luminal fluid catecholamines). Both subtypes were dense in the membr anes of smooth muscle cells from renal arteries. Concordant data were obtai ned by radioligand binding and immunoblotting of membranes prepared from co rtical and medullary portions of the kidney. Conclusion. Our data provide an immunohistochemical basis for the cellular targets of beta -adrenergic regulation of renal function. Moreover. they co uld help to devise therapeutic strategies directed at renal beta -ARs.