Dissociation of Hemodynamic and Renal Effects of i.v. α-hANF (99-126) in Conscious Calves

Summary

The effects of i.v. human atrial natriuretic factor (α-hANF [99-126]) was investigated in 5 conscious calves (age 4 months, weight 94±14kg) with constant fluid (300 ml/h) and sodium intake over a period of 24 hours before and during the 3 hours of experimentation. We administered 200 μg, 400 μg and 800 μg ANF at hourly intervals. Immediately (+2 min) after the i.v. injection the peptide's serum-concentration rose from, basal 13±3 to 802±191 (200 μg), 1707±419 (400 μg) and 3483±878 pmol/l (800 μg) (p<0.0001), respectively. Mean arterial pressure decreased from, basal, 108±18 to 85±17, 76±16 and 69±18 mmHg (p<0.0001), and central venous pressure decreased from, basal, 5.1±3 to 1.2±1, 0.4±1 and 0.8±2 mmHg (p<0.0001). Heart rate increased from, basal, 66±5 to 84±23, 111±29 and 114±13b/min (p<0.0001). Following the administration of ANF the urine volume decreased from, basal, 261±145 to 195±72, 121±41 and 102±33 ml/h (p<0.0041). The urinary sodium excretion rates decreased from, basal, 50±17 to 30±13, 22±10 and 19±10 mmol/h (p<0.0007), and the potassium excretion rates decreased from, basal, 43±19 to 39±16, 26±11 and 23±10 mmol/h (p<0.0047). Endogenous clearance of creatinine (basal: 182±30 ml/min) did not change (260±84, 218±66 and 224±76 ml/h) following i.v. ANF. Inspite of this marked fluid retention, the hematocrit, expressed as relative change, was increased by 7.5%, 11.8% and 10.4%. In 2 calves we additionally measured an increased whole blood and plasma density possibly indicating increased liquid permeation to an extravascular compartment. Thus, in calves the hemodynamic effects of ANF are comparable to those seen in man. However, the failure of ANF to stimulate diuresis and natriuresis indicates a dissociation of hemodynamic and renal effects of ANF in calves.

Key words

Calf - Atrial Natriuretic Factor - Bolus Application - Renal Effect - Hemodynamic Effect