A Comparison of Synthetic Rat and Human Atrial Natriuretic Factor in Conscious Dogs

The renal and hypotensive responses to intravenous infusions of 10, 50, 100, and 200 pmol/kg/min of synthetic rat atrial natriuretic factor (Argl0l-Arg-Ser-Ser-Cys-Phe-Gly-Gly-Arg-Ile”°-Asp-Arg-Ile-Gly-Ala-Gln-Ser-Gly-Leu-Glyl20-Cys-Asn-Ser-Phe-Arg-Tyr; disulfide bond between cysteines) were compared with those produced by synthetic human atrial natriuretic factor (Met110) in five conscious dogs. Increasing doses of rat or human atrial natriuretic factor lowered mean arterial pressure in a dose-related manner. At 200 pmol/kg/min, the maximally effective dose for both peptides, mean arterial pressure was reduced from 116 ± 4 to 96 ± 5 mm Hg and from 117 ± 5 to 100 ± 3 mm Hg (p < 0.01), respectively. Neither peptide affected heart rate. Fractional sodium excretion increased from 0.69 ± 0.22 to 3.95 ± 1.23% and from 0.69 ± 0.16 to 4.62 ± 0.72% during infusions of 200 pmol/kg/min of rat and human atrial natriuretic factor, respectively. Urine volume and fractional chloride excretion rose during infusions of rat or human atrial natriuretic factor in a manner that resembled the elevation in sodium excretion. The stimulation of fractional potassium excretion by both rat and human peptides was more variable and not as clearly dose-dependent. Glomerular filtration rate was enhanced by both rat and human atrial natriuretic factor, while neither peptide significantly changed renal plasma flow. Arterial plasma renin activity fell from 1.4 ± 0.4 to 0.6 ± 0.2 ng/ml/hr during administration of 200 pmol/kg/min of rat atrial natriuretic factor and from 0.8 ± 0.4 to 0.2 ± 0.2 ng/ml/hr during 100 pmol/kg/min of human atrial natriuretic factor. In conclusion, synthetic rat and human atrial natriuretic factor (101–126) peptides appear to elicit comparable degrees of hypotension, saluresis, diuresis, and renin inhibition in conscious dogs.