Pressure Dependence of Atrial Natriuretic Peptide During Norepinephrine Infusion in Humans

SUMMARY The relative contribution of increased blood pressure (BP) or norepinephrine (NE), or both, to the stimulatory effect of an NE pressor infusion on circulating immunoreactive atrial natri-uretic peptide (ANP) was evaluated in 10 healthy young men. They were studied during an infusion of NE, which was applied initially alone and then in combination with sodium nitroprusside. NE infusion rate was increased in four 30-minute intervals to a final dose of 200 ng/kg body weight per minute, leading to 12-fold higher plasma NE levels than were seen during control conditions. This increased mean BP (from a mean basal value of 94 ± 3 to 119 ± 4 [SEM] mm Hg; p<0.001) and plasma immunoreactive ANP (from 50 ± 7 to 112 ± 17 pg/ml; p<0.001), whereas heart rate decreased ( p < 0.001). The NE infusion was continued at the highest dose and an additional infusion of sodium nitroprusside was started to titrate mean BP in 30-minute intervals down to control values; a mean sodium nitroprusside dose of 0.95 /ug/kg/min restored mean BP to 93 ± 4 mm Hg (p<0.001), de-creased plasma immunoreactive ANP to basal values (51 ± 4 pg/ml; p<0.001), increased heart rate ( p < 0.001), and left plasma levels of NE largely unchanged. Plasma protein and hematocrit rose about 5 to 6 % (p<0.001) during the NE infusion and then decreased about 3 to 4 % (p<0.001 and p<0.01) when sodium nitroprusside was added. No consistent changes were observed for plasma levels o