A ring-deleted analog of atrial natriuretic factor--des[Gln18, Ser19, Gly20, Leu21, Gly22] ANF4-23-NH2 (C-ANF4-23)--binds with high affinity to approximately 99% of ANF receptors in the isolated perfused rat kidney. In this preparation, C-ANF4-23 is devoid of detectable renal effects and does not antagonize any of the known renal hemodynamic and natriuretic actions of biologically active ANF1-28. In contrast, both C-ANF4-23 and ANF1-28 increase sodium excretion and decrease blood pressure in intact anesthetized rats. This apparent contradiction is resolved by the finding that the ring-deleted analog markedly increases plasma levels of endogenous immunoreactive ANF in the rat. The results show that the majority of the renal receptors of ANF are biologically silent. This new class of receptors may serve as specific peripheral storage-clearance binding sites, acting as a hormonal buffer system to modulate plasma levels of ANF.

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