The purpose of this study is to determine whether chronic removal of atrial appendages alters renal response to volume expansion in the conscious monkey. Chronic bilateral atrial appendectomy (ATX) was performed in six animals. Six additional animals served as sham-operated controls. Monkeys were studied 1-2 wk after chronic surgery. The protocol consisted of three consecutive 10-min urine collections followed by 20% ischemic blood volume expansion (VE) and 120 min of post-VE measurements. In sham animals, VE caused an increase in plasma atrial natriuretic peptide (ANP) levels (48 +/- 7 pg/ml to a peak of 108 +/- 34 pg/ml). Urine flow increased from 0.43 +/- 0.07 to 1.07 +/- 0.24 ml/min, sodium excretion increased from 17.9 +/- 2.6 to 74.9 +/- 12.0 mu eq/min, and fractional sodium excretion increased from 0.67 +/- 0.10 to 2.43 +/- 0.28%. ATX attenuated the increase in ANP (34 +/- 8 pg/ml to a peak of 38 +/- 9 pg/ml) in four of six animals. In these animals, renal response to VE was significantly attenuated. Urine flow increased from 0.21 +/- 0.05 to 0.30 +/- 0.01 ml/min, sodium excretion increased from 19.3 +/- 6.02 to 37.8 +/- 5.05 mu eq/min, and fractional sodium excretion increased from 0.79 +/- 0.08 to 1.43 +/- 0.17%. Renal response of two ATX animals with normal increases in atrial natriuretic factor was similar to the sham group. Effect of volume expansion on mean arterial pressure, central venous pressure, and renal hemodynamics was not altered by ATX. These findings demonstrate that bilateral atrial appendectomy in the monkey attenuates the increase in ANP and reduces renal response to VE.