Specific binding activities and cyclic GMP responses by atrial natriuretic polypeptide in kidney epithelial cell line (LLC-PK 1)

Abstract

Receptor binding activities and cyclic GMP responses by α-human atrial natriuretic polypeptide (α-hANP) and its fragments were studied in a kidney epithelial cell line (LLC-PK 1). Binding of 125I-α-hANP to the cells at 0°C was saturable, time-dependent and reversible, indicating the presence of a single class of binding sites. α-hANP (7–23) NH 2 fragment inhibited most effectively the specific binding of 125I-α-hANP to the LLC-PK 1 cells, followed by α-hANP (17–28) and α-hANP (8–22), while α-hANP (1–6) and α-hANP (24–28) did not. α-hANP stimulated the formation of cyclic GMP in the LLC-PK 1 cells dose-dependently. Although no fragments of α-hANP used were effective for cyclic GMP formation in the LLC-PK 1 cells, α-hANP (7–23) NH 2 antagonized the action of α-hANP on cyclic GMP formation. These data suggest that the LLC-PK 1 cells retain specific receptors for atrial natriuretic polypeptide (ANP) and respond to ANP by stimulating cyclic GMP formation, and therefore this cell line may be useful for studying the mechanism of action for ANP in renal tubular cells.