Binding of synthetic β‐human atrial natriuretic peptide to cultured rat vascular smooth muscle cells

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Abstract
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.