We have studied the effects of synthetic β-human atrial natriuretic peptide (β-hANP), an antiparallel dimer of α-hANP, on receptor binding and cGMP generation in cultured rat vascular smooth muscle cells and compared the effects with those of α-hANP. Characteristics of temperature-dependent binding and degradation of 125I-β-hANP were similar to those 125I-α-hANP. Scatchard analysis indicated a single class of binding sites for β-hANP with a maximal binding capacity one-half that of α-hANP. Parallel and antiparallel dimers were equipotent in inhibiting the binding and stimulating intracellular cGMP formation, of which the maximal effect was about one-half that of α-hANP. Reverse-phase high performance liquid chromatography revealed that most of β-hANP added to cells was converted to a small molecular mass component corresponding to α-hANP after incubation. These data suggest that the less potent effect of β-hANP in receptor binding and cGMP generation may be partly accounted for by the possible conversion of β-HANP to α-hANP at the site of target cells.
