DISSOCIATION OF HEMODYNAMIC AND RENAL EFFECTS OF IV ALPHA-HANF (99-126) IN CONSCIOUS CALVES

The effects of i.v. human atrial natriuretic factor (alpha-hANF [99-12 6]) was investigated in 5 conscious calves (age 4 months, weight 94 +/ - 14 kg) with constant fluid (300 ml/h) and sodium intake over a perio d of 24 hours before and during the 3 hours of experimentation. We adm inistered 200 mug, 400 mug and 800 mug ANF at hourly intervals. Immedi ately (+ 2 min) after the i.v. injection the peptide's serum-concentra tion rose from, basal 13 +/- 3 to 802 +/- 191 (200 mug), 1707 +/- 419 (400 g) and 3483 +/- 878 pmol/l (800 mug) (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 pressur e decreased from, basal, 5.1 +/- 3 to 1.2 +/- 1, 0.4 +/- 1 and 0.8 +/- 2 mmHg (p < 0.000 1). Heart rate increased from, basal, 66 +/- 5 to 8 4 +/- 23, 111 +/- 29 and 114 +/- 13 b/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 ur inary sodium excretion rates decreased from, basal, 50 +/- 17 to 30 +/ - 13, 22 +/- 10 and 19 +/- 10 mmol/h (p < 0.0007), and the potassium e xcretion rates decreased from, basal, 43 +/- 19 to 39 +/- 16, 26 +/- 1 1 and 23 +/- 10 mmol/h (p < 0.0047). Endogenous clearance of creatinin e (basal: 182 +/- 30 ml/min) did not change (260 +/- 84, 218 +/- 66 an d 224 +/- 76 ml/h) following i.v. ANF. Inspite of this marked fluid re tention, the hematocrit, expressed as relative change, was increased b y 7.5%, 11.8% and 10.4%. In 2 calves we additionally measured an incre ased whole blood and plasma density possibly indicating increased liqu id permeation to an extravascular compartment. Thus, in calves the hem odynamic effects of ANF are comparable to those seen in man. However, the failure of ANF to stimulate diuresis and natriuresis indicates a d issociation of hemodynamic and renal effects of ANF in calves.