Atrial natriuretic peptide increases human capillary filtration and venous distensibility

OBJECTIVE: The main aim of this study was to examine whether atrial natriuretic peptide (ANP) alters capillary filtration and venous distensibility. DESIGN: The study was designed to examine the local effects of i.a. infusion of ANP upon capillary filtration and venous distensibility in human forearms of eight healthy volunteers. METHODS: Using a water plethysmograph, we measured venous distensibility and capillary filtration from changes in forearm volume when transmural venous pressure was increased in a stepwise manner and held constant during i.a. infusion of saline, ANP and sodium nitroprusside (SNP). The doses of ANP and SNP were chosen to double baseline forearm blood flow obtained during saline infusion. RESULTS: ANP and SNP infusion both increased venous distensibility to the same extent compared with saline infusion. Capillary filtration was greater during ANP than during saline or SNP infusion. Small vein pressure was comparable during infusion of the two drugs. CONCLUSION: Our results suggest that ANP increases venous distensibility and capillary filtration in human forearms.