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pp.34-50
The present study was undertaken to evaluate the antagonistic effects of water extracts of Chinese gooseberry (Actinidia chinensis P.) root on the natriuretic peptide receptor system in the rat kidney. By using in vitro receptor autoradiography, specific 125I-atrial natriuretic peptide (125I-ANP) binding sites were localized in glomerulus, inner medulla, intrarenal artery, vasa recta bundle, and renal pelvis of Sprague Dawley rat kidney. These specific bindings were competitively displaced by water extracts of Chinese gooseberry root in a dose dependent manner. Also, productions of 3',5'-cyclic guanosine monophosphate (cGMP) by activation of particulate guanylyl cyclase (GC) were stimulated by ANP in the glomerular and inner medullary membranes from rat kidney. These cGMP productions were inhibited by water extracts of Chinese gooseberry root in a dose dependent manner. The inhibitory effect of water extracts of Chinese gooseberry root on activation of GC was more potent rather than on 125I-ANP bindings to these renal structures. From affinity cross-linking study, the water extracts of Chinese gooseberry root inhibited the 125I-ANP labeling of GC-coupled natriuretic peptide receptor from renal glomerulus. Intravenous infusion of ANP elicits a potent diuresis, and urinary sodium and
chloride excretions in New Zealand White rabbit. The pre-treatment of intravenous water extracts of Chinese gooseberry root infusion decreased competitively various renal effects of ANP with out changes in systemic hemodynamics. These results indicate that the water extracts of Chinese gooseberry root specifically inhibits the GC-coupled natriuretic peptide receptor subtypes (NPR-A), and suggest that the water extracts of Chinese gooseberry root may contain an antagonistic molecule regulating the biological functions of ANP system in the kidney and other organs.
