Brain natriuretic peptide binding sites in rat kidney.

Specific binding sites for [125I] porcine brain natriuretic peptide-26 ([125I]BNP-26) were investigated in the rat kidney by using receptor autoradiographic and membrane binding techniques. The binding sites were discretely localized in the glomeruli and inner medulla. There were no differences between the localization of [125I] BNP-26 and [125I] alpha-rat ANP binding sites. [125I]BNP-26 binding to solubilized membranes from isolated glomeruli of the rat kidney was saturable, and a single class of high-affinity sites. [125I]BNP-26 bound to two sites in solubilized inner medullary membranes. The rank order of potency to inhibit binding was BNP-26 = alpha-rat ANP (1-28) greater than atriopeptin III [ANP-(103-126)] much greater than atriopeptin I [ANP(103-123)] greater than des-Cys105, Cys121-ANP-(104-126). The possibility that BNP-26 regulates, as a circulating hormone, kidney functions by binding to ANP receptors would have to be considered.